注册 English

Emerging two-dimensional nanocatalysts for electrocatalytic hydrogen production

Hong Chen ,  Yansong Zhou ,  Wei Guo ,  Bao Yu Xia

downloadPDF
Citation:  Hong Chen, Yansong Zhou, Wei Guo, Bao Yu Xia. Emerging two-dimensional nanocatalysts for electrocatalytic hydrogen production[J]. Chinese Chemical Letters, 2022, 33(4): 1831-1840. doi: 10.1016/j.cclet.2021.09.034 shu

Emerging two-dimensional nanocatalysts for electrocatalytic hydrogen production

English

  • 1. Introduction

    In recent years, the exponentially increased population and rapidly developed industrialization have raised the energy demand of human society [1]. Due to the exhaustion and environmental pollution of traditional fossil fuels, the exploration of alternative green energy carriers has drawn massive attention [2]. Hydrogen is considered as a promising clean energy carrier owing to its renewability and remarkable gravimetric energy density (140 MJ/kg) [3, 4]. Generally, hydrogen can be produced by photocatalytic and electrochemical water splitting, steam reforming process, iodinesulfur cycle, and so on [5, 6]. Compared to other technologies, electrocatalytic water splitting driven by sustainable energy would be more promising [7, 8].

    Like many chemical reactions, the electrochemical hydrogen evolution reaction (HER) requires high energy input called overpotential to overcome the barrier. Suitable catalysts are necessary to minimize the overpotential for HER. Generally, homogeneous catalysts have identified active sites with high catalytic activity and selectivity, but they usually have drawbacks of undesirable durability and post-reaction separation [9]. By contrast, heterogeneous catalysts have several advantages over homogeneous ones, and they are considered as potential candidates [10]. Among them, metal-based catalysts, especially noble metals such as platinum, has a minimized free energy for hydrogen absorption and reduced overpotential for hydrogen production. However, the rarity and expensive nature of noble metals limit their practical application in largescale water electrocatalysis. Thereby, various earth-abundant catalysts have been considered in different nanostructured architectures, including nanoparticles, nanowires, nanosheets, nanotubes, nanobelts, superlattices, etc. [11, 12]. Particularly, nanomaterials in two-dimension (2D) have emerged as a hotspot for nanocatalysts due to their unique structure as well as remarkable physical and electronic properties [13].

    In the past few years, 2D materials play an increasingly important role in efficient water electrolysis for hydrogen production, it is necessary to comprehensively summarize their research progress of 2D nanocatalysts for hydrogen evolution. In this feature review, we first introduce the fundamentals and performance evaluation criteria of HER. Then, the advances of 2D electrocatalysts in electrochemical HER will be discussed in details. The 2D electrocatalysts are classified into organic composites, such as metal organic frameworks (MOFs) [14, 15], covalent organic frameworks (COFs) [16]; and inorganic nanocatalysts, including metallic nanomaterials [17], metal-free nanomaterials [18, 19], transition metal dichalcogenides (TMDs) [20, 21], MXenes [22] and layered double hydroxides (LDHs) [23]. Their synthetic methodologies, modification strategies, and reaction mechanisms are summarized in this specific section. Finally, perspectives regarding the furtherance of this blossoming field are proposed. We hope this review will provide a comprehensive understanding of 2D nanocatalysts for electrochemical HER, which could promote the development of hydrogen energy technologies towards sustainable human society (Fig. 1).

    Figure 1

    Figure 1.  Hydrogen production by electrolysis of water splitting.
    DownLoad: Full-Size Img PowerPoint

    2. Fundamentals of HER

    2.1 Reaction mechanism

    Electrochemical HER is the cathodic reaction of water electrolysis in acidic or alkaline media, where three possible elementary steps are involved. The HER occurred in acidic media can be depicted by two serial steps (Fig. 2a). It begins with the electrochemical adsorption of hydrogen (Had) on electrode surface (Eq. 1, Volmer step). The immobilized hydrogen species are derived from the combination of free electrons and proton donors, i.e., hydronium ions (H3O+) in acidic electrolyte. Subsequently, hydrogen gas can be generated following the desorption process, where another proton binds to Had and is reduced by another free electron (Eq. 2, Heyrovsky step), or/and the coupling of two Had (Eq. 3, Tafel step) [24, 25].

    		 (1)

    		(2)

    		(3)

    Figure 2

    Figure 2.  Mechanism of HER on the surface of 2D materials in (a) acidic and (b) alkaline media.
    DownLoad: Full-Size Img PowerPoint

    Akin to the reaction in acidic media, the HER occurred in alkaline media is composed by two crucial steps (Fig. 2b): the first one is generation and immobilization of Had (Eq. 4, Volmer step) and the second one is desorption process of H2 evolution. Unlike in acidic electrolyte, the proton donors in alkaline electrolyte are obtained from the dissociation of H2O molecules. The absorbed Had can be conducted via Heyrovsky step (Eq. 5, Heyrovsky step) or Tafel step (Eq. 6, Tafel step) and both to yield H2 [26].

    		 (4)

    		(5)

    		(6)

    2.2 Evaluation criteria of HER catalysts

    2.2.1   Volcano plot

    According to the Sabatier principle, the interaction between HER electrocatalysts and intermediates (Had and H2) should be appropriate [25]. Fast Had adsorption and H2 desorption facilitate the HER kinetics. From the physicochemical points of view, the Had adsorption and H2 desorption can be evaluated by Gibbs free energy. The function between the experimentally measured exchange current density (j0) of HER and the calculated Gibbs free energy (△GH*) of the adsorbed hydrogen atoms on various metals can be plotted (Fig. 3a) [25]. This proposed "volcano-type" plot defines the best HER activity at the top with △GH* = 0, where the catalytic performance of Pt metal is identified to be prior to others. It also provides a strong theoretical basis for evaluating the kinetic activity of the catalysts [27]. With the development of computational science and theoretical calculations, more valuable information of △GH* about HER electrocatalysts have been achieved [28].

    Figure 3

    Figure 3.  (a) A volcano plot of experimentally measured exchange current density as a function of △GH*. Reproduced with permission [25]. Copyright 2014, the Royal Society of Chemistry. (b) Schematic illustration of the HER energetics. Reproduced with permission [27]. Copyright 2019, Wiley-VCH. (c) Schematic HER polarization curves on different electrocatalysts. Reproduced with permission [27]. Copyright 2019, Wiley-VCH.
    DownLoad: Full-Size Img PowerPoint
    2.2.2   Overpotential

    Basically, the reaction of water splitting in the electrochemical cell can start with a Nernst potential under the ideal standard temperature and pressure conditions. However, a greater potential is usually required in practical HER to overcome the energy barrier. The difference between practical potential and Nernst potential is called overpotential η (Fig. 3b). Consequently, the efficiency of water electrolysis is limited by the kinetic barrier for water dissociation. Minimizing the overpotential of HER is important for the further development of hydrogen economy.

    2.2.3   Tafel equation

    The Tafel equation can be used to describe the current-potential relationship under an apparent overpotential η, as described in Eq. 7, where j is the current density, j0 represents the exchange current density, and b is the corresponding Tafel slope [29].

    		 (7)

    The Tafel slope b represents the potential difference required to increase or decrease the current density tenfold. The HER reaction mechanism can be inferred through the experimentally measured Tafel slope [30].

    The exchange current density j0 is another important kinetic parameter in HER, which determines the electrochemical reaction rate under a certain applied potential (Fig. 3c) [27]. The ideal electrocatalysts with minimized Tafel slope and high exchange current density are taken together suggesting favorable reaction kinetics for electrochemical HER [31, 32].

    2.2.4   Stability

    The stability refers to the activity evolution of the catalyst over time. Because the electrocatalysts may experience chemical or structural alterations during operational use. Inadvertently, their stability in HER may be affected. Thus, measuring the electrocatalyst stability is important. The chronopotentiometry (current-time curve) or chronoamperometry (potential-time curve) and repetitive cyclic voltammetry (CV) measurements are usually used for evaluating the stability [33]. In the former two methods, a current density of 10 mA/cm2 is commonly applied as the descriptor, the catalytic stability can be assessed by the current or potential decay during the durability test. As for the CV test, the stability is evaluated by comparing the polarization curves before and after a continuous CV cycle (usually 500–10, 000 cycles).

    2.2.5   Faradic efficiency

    Faradaic efficiency (FE) describes the efficiency of charge transfer for target reaction in an electrochemical reaction system, which dictates the selectivity of electrocatalysts. FE is defined as the ratio of effective charge transfer to the total charge consumed in HER. The HER electrocatalyst with ideal FE can increase the productivity of H2 and eliminate the extra cost of product separation and purification. Generally, the actual H2 output measured by gas chromatography or water gas displacement method is compared with the theoretical H2 output calculated by constant current or constant potential electrolysis to calculate the FE of HER [34].

    3. 2D electrocatalysts for HER

    2D materials have diversified in many applications dictated by their unique atomic structure and intrinsic physical properties. The allure of 2D electrocatalysts in HER can be mapped to three aspects including specific surface area, 2D planer structure and electronic conductivity. 2D materials have maximal surface to bulk ratio, providing abundant active sites for hydrogen adsorption, and the atomically thin thickness guarantees the rapid transfer of free electrons. Besides, the open 2D planes can be directly modified by heteroatom doping, defect engineering, surface functionalization, and composite construction, resulting in enhanced electrochemical HER performance. The 2D electrocatalysts are classified into organic composites, such as metal organic frameworks (MOFs), covalent organic frameworks (COFs); and inorganic nanocatalysts, including metallic nanomaterials, metal-free nanomaterials, transition metal dichalcogenides (TMDs), MXenes and layered double hydroxides (LDHs). The corresponding synthetic protocols, modification strategies, and structure-performance relationship are discussed below.

    3.1 2D organic materials

    2D organic materials possess a periodic network of repetitive organic units arranged along two orthogonal directions in an isolated sheet structure, which endows them outstanding advantages including molecular diversity and adjustable functionality [35, 36]. The MOFs, COFs and a variety of their modified derivatives, are efficient electrocatalysts for HER.

    3.1.1   Covalent organic frameworks (COFs)

    The COFs are generally assembled by strong covalent conjunction between light elements such as carbon, nitrogen and oxygen with reticular arrangement [37]. The intimate interlayer electronic interactions within the porous COFs structures ensure the high electrical conductivity and facile electron migration across abundant catalytic sites, which make them promising catalysts in electrochemical HER [38-40]. Chen group reported porphyrin-based COF nanosheets for electrochemical HER in 1 mol/L KOH, with an overpotential of 398 mV and a small Tafel slope of 161 mV/dec, as well as the slight current attenuation (16.4%) after chronopotentiometry test for 10 h. The linkage between active centers of COF and butadiyne facilitates the charge migration across the electrodeelectrolyte interface thus promotes the progress of HER (Fig. 4a) [41]. However, the lack of active sites in pristine 2D COFs limits the catalytic performance. Theoretical studies by Ball et al. proved that the bipyridine-linked co-doped COFs with heteroatoms of silicon and phosphorus manifested facile charge transfer kinetics and desirable hydrogen atom adsorption Gibbs free energy (Fig. 4b) [42]. Doping with metal species also augments HER activity. Maiti et al. prepared Ru doped COFs with a positive onset potential of 159 mV in 1.5 mol/L H2SO4 and remarkable stability with negligible change of exchange current density and polymeric framework after 100 cycles. The incorporation of Ru increases the flexibility of the COFs structure and accelerates charge transfer (Fig. 4c) [43]. Besides, the heteroatom-doped COFs are promising precursors for fabricating heteroatom-doped carbon-based electrocatalysts [44]. Such COF-derived carbon materials have a spectrum of uniformly dispersed active sites, excellent stability, ordered porous and covalent conjunction structure, all of which are favorable merits for HER [45].

    Figure 4

    Figure 4.  (a) The TEM images of Co-COF and COF. Reproduced with permission [41]. Copyright 2019, the Royal Society of Chemistry. (b) Volcano plot of the average △GH* values of different catalysts. Copied with permission [42]. Copyright 2020, American Chemical Society (c) Impedance curves of the COF and Ru@COF. Copied with permission [43]. Copyright 2020, Wiley-VCH. (d) The structure of the MOF composing of CoO6 octahedra coordinated in a plane to ligands. Reproduced with permission [46]. Copyright 2019, Wiley-VCH. (e) The catalysis mechanism of HER in alkaline solution on the Co-MOF/MoS2 nanosheets. Copied with permission [54]. Copyright 2019, Wiley-VCH. (f) The charge density of Ni-BDC and NiRu0.13-BDC. Reproduced with permission [57]. Copyright 2021, Springer Nature.
    DownLoad: Full-Size Img PowerPoint
    3.1.2   Metal organic frameworks (MOFs)

    The MOFs with metal centers immobilized by organic ligands are an emerging class of porous layered materials. The tailorable nature by replacing the coordinated metal sites or organic linkers makes the ideal candidates in diverse heterogeneous catalytic processes (Fig. 4d) [46-48]. The MOFs in possession of porous structure, abundant metal active sites and excellent electrical conductivity, are another group of potential catalysts for HER [49-51]. Compared with single-metal center MOF catalysts, the bimetallic center MOF catalysts have more active sites. The synergistic effects between the bimetallic metal nodes can accelerate the reaction kinetics [52]. While the pristine MOFs suffer from high overpotential, hybrid MOF-based electrocatalysts have outstanding efficiency in HER originating from the synergistic effect between MOFs and foreign materials, as a result of optimized △GH* of the intermediate products, improved electrical conductivity, enhanced intrinsic catalytic activity and increased number of active sites [53].

    Zhu et al. reported the novel Co-BDC (C8H4O4)/MoS2 hybrid nanosheets from a facile sonication-assisted solution method, with an onset overpotential of only 155 mV and negligible potential shift of the polarization curve after 2000 CV cycles in Ar-saturated 1.0 mol/L KOH solution [54]. The MOF nanosheets facilitate the adsorption and dissociation of H2O molecules to provide abundant protons for the adjacent MoS2. Subsequently, the MoS2 nanosheets provide essential reaction active sites for H2 desorption and generation (Fig. 4e). Adding conductive materials or introducing extra metallic sites is another choice for optimizing the HER performance of MOF-based electrocatalysts [51, 55, 56]. Sun et al. introduced Ru single atoms into MOF materials, which exhibited a low overpotential of 36 mV at the current density of 10 mA/cm2 in 1 mol/L phosphate buffered saline solution. A tiny current decrease was observed after 30 h test and the faradic efficiency was estimated to be approximately 100% [57]. The dispersed Ru atoms provide extra active sites, and further modulate the electronic structure of the active centers for better H2O and H* adsorption (Fig. 4f). Likewise, Dong et al. selectively doped the molecular metal dithiodiamine into MOFs and gained the best performance among the same type of catalysts in 0.5 mol/L H2SO4 solution [58]. The integration of homogeneous metal complexes and heterogeneous MOFs enriches the catalytic active sites, as well as optimizes the adsorption and desorption energy of H through the strong coordination interaction. Akin to above mentioned COF materials as precursors for heteroatom-doped carbon catalysts, various metal-carbon catalysts with heteroatoms can derive from MOFs, such as single-metal/bimetallic-based electrocatalysts, metal oxides/sulfides electrocatalysts and their hybrids [59-61].

    3.2 2D inorganic materials

    2D inorganic electrocatalysts have many unique physicochemical properties, especially large surface area, short ion and charge transfer path, flexible and controllable compositions and structures, ultra-thin thickness and easy functionalization, which make them promising candidate materials for HER [62, 63]. In addition to the inorganic 2D metal-carbon hybrid composites derived from their corresponding MOF precursors, there are a wide variety of 2D inorganic electrocatalysts for electrochemical HER encompassing 2D metallic nanomaterials, 2D metal-free material, MXenes, TMDs and LDHs, as discussed in the following sections.

    3.2.1   2D metallic nanomaterials

    Recently, emerging 2D metallic nanomaterials composed of bare metal elements of multiple atomic sizes have attracted more attention and enriched the diversity of 2D materials [64]. 2D metal nanomaterials can be prepared through various methods, such as organic ligand-assisted growth, small-molecules-andions-mediated synthesis, 2D template-confined synthesis, seeded growth, photochemical synthesis, hydrothermal/solvothermal synthesis and exfoliation (Fig. 5a) [64, 65]. 2D metal nanosheets are potential candidates as hydrogen evolution catalysts owing to their innate electrical conductivity and electrochemical stability [64, 66, 67]. However, the current research of such electrocatalysts is limited in noble metals [68, 69]. Other electrocatalysts from earth-abundant metals need to be developed. Li et al. constructed IrRh metal nanosheets with an astonishingly low overpotential of 35 mV at current density of 10 mA/cm2 in 1.0 mol/L KOH solution, outperforming the commercial Pt/C catalysts (46 mV) (Fig. 5b). The electronic structure effect between Ir and Ru helps optimize the adsorption states and charge transfer properties [70].

    Figure 5

    Figure 5.  (a) Schematic showing of the fabrication of metal nanosheets. Copied with permission [65]. Copyright 2016, Wiley-VCH. (b) HER polarization curves for different catalysts. Copied with permission [70]. Copyright 2019, American Chemical Society. (c) The formation enthalpies values of RhPd and RhPd-H. Reproduced with permission [71]. Copyright 2020, American Chemical Society. (d) The HRTEM image of PtAgCo nanosheets. Reproduced with permission [72]. Copyright 2017, American Chemical Society. (e) Schematic representation for 2D-Pt on LDH synthesis and its application. Copied with permission [73]. Copyright 2020, American Chemical Society. (f) 2D suspended 10-fold material with quantities of defects in difference. Reproduced with permission [74]. Copyright 2019, American Chemical Society.
    DownLoad: Full-Size Img PowerPoint

    The catalytic performance of bare bimetallic nanosheets can be further improved by heteroatom doping with additional catalytic sites and altered the electronic structure. Fan et al. introduced H atoms into bimetallic RhPd nanosheets, resulting in a prominently low overpotential of 40 mV and predominant stability for over 10 h at 100 mA/cm2 in 1 mol/L KOH solution. The confined H stabilizes the RhPd nanosheets bimetallene and enhances the activity (Fig. 5c) [71]. Mahmood et al. prepared ultrathin porous PtAgCo nanosheets by doping Co into PtAg alloy. The Co atoms change the electronic structure of the PtAg alloy and contribute to the desorption of Had by downshifting the Fermi level of PtAg (Fig. 5d) [72].

    Loading porous Pt nanosheets onto nickel hydroxide iron sheets leads to fast charge migration and diffusion of electrolyte ions at an intimate 2D-2D interface (Fig. 5e) [73]. Yadav et al. combined 2D Al alloys in 2-fold decagonal quasicrystalline symmetry with WS2, forming a heterostructure with stack faults (Fig. 5f), as a result of enlarged the active areas. The hybrid catalyst manifested a low overpotential of 60 mV and long-term stability in the solution of 0.5 mol/L H2SO4 [74]. It is worthy noting that fabricating 2D metallic material-based composite can reduce the capital cost. This is expected to be applied in large-scale industry.

    3.2.2   2D metal-free alkenes

    Graphene is defined as a 2D honeycomb planar monolayer of carbon atoms with outstanding physical and chemical properties [75, 76]. While pristine graphene is electrochemically inert and exhibits negligible HER activity over a stable and large window. Chemically modified graphene, has been verified to exhibit improved electrocatalytic HER performance. For example, a suitable △GH* of 0.08 eV for the initial H* adsorption could be obtained over the N, P co-doped graphene (Fig. 6a) [18]. Hu et al. proposed the proton-penetration process over N-doped graphene wrapped NiCu bimetallic sheets. The number of the covered graphene layers were closely related to the HER activity of the catalyst. The penetrating ability of protons determined the HER activity. The graphene-cover strategy can also prevent the metal nanoparticles from corrosion in strong alkaline environment (Fig. 6b) [77]. Moreover, the graphene matrix composites by coupling alternating active MoS2 with reduced graphene oxides layers showcased excellent catalytic activity with a low onset overpotential of 140 mV and a large current density of 23 mA/cm2 at 200 mV in 0.5 mol/L H2SO4. The outstanding catalytic HER performance of MoS2/graphene composites descends from the sufficiently high exposure of active edge sites and high conductivity of graphene substrate [78].

    Figure 6

    Figure 6.  (a) Calculation of △GH* values for N- and/or P-doped graphene. Reproduced with permission [18]. Copyright 2014, American Chemical Society. (b) Probable HER mechanisms for graphene-covered metal catalysts. Copied with permission [77]. Copyright 2021, Springer Nature. (c) The atomic structures of H2O, H–OH, HO, and the corresponding adsorption free energies of different catalysts. Reproduced with permission [83]. Copyright 2019, American Chemical Society. (d) In-situ HR-TEM images of CoFeO@BP during HER. Copied with permission [84]. Copyright 2020, Wiley-VCH. (e) TEM image of a typical MoS2-BP nanosheet. Reproduced with permission [85]. Copyright 2017, American Chemical Society. (f) Charge transfer which induces a bound donor-defect complex between hydrogen and armchair edge. Reproduced with permission [86]. Copyright 2019, American Chemical Society.
    DownLoad: Full-Size Img PowerPoint

    Black phosphorus (BP) is a layered semiconductor composed of corrugated planes of phosphorus atoms with strong interlayer chemical bonding, high mobility, tunable band gap, large active surface area and abundant reserves on earth [79-81]. The honeycomb structure of BP can help to expose the lone pair electrons of metals. This strong activation effect of BP on metal atoms can improve the HER activity. Wang et al. bonded BP to Pt with an optimal △GH* of −0.02 eV, approximately towards to zero. This arose from the strong Pt-P interaction and remarkable durability of Pt-P bonds [82]. Li et al. further introduced Ru metal to BP-Pt catalyst, which exhibited greatly enhanced HER activity with a prominent overpotential of 22 mV at 10 mA/cm2 in a 1 mol/L KOH solution, much lower than that of commercial Pt/C (77 mV) and Pt NCs/BP (64 mV). The electrons accumulate on the hybrid interface, leading to shortage of electrons on Ru. Thus, the Ru atoms are favorable to the electron-rich H2O* and HO* species, resulting in moderate binding strength (Fig. 6c) [83].

    In addition, the BP could be a splendid substrate or modifier for constructing composite electrocatalysts, of which the electronic structure and conductivity of the hybrids can be tuned. For example, the CoFe oxide grown on BP substrate via a facile solvothermal strategy, exhibiting an overpotential of 88 mV at 10 mA/cm2 in 1 mol/L KOH solution. The metastable amorphous CoFe oxide can be turned to different active states during redox reactions and CoFe phosphides can be formed on BP substate as active centers of HER (Fig. 6d) [84]. Similarly, He et al. deposited active MoS2 on BP to construct a MoS2-BP heterogeneous interface (Fig. 6e). The hybrid catalyst exhibited an overpotential of 85 mV at 10 mA/cm2 and less than 3% degradation of current density after 10, 000 s in the media of 0.5 mol/L H2SO4. The electrons accumulated on MoS2 promote the coupling of electrons and protons at the catalyst-electrolyte interface, accelerating electron and mass transfer. Hence the kinetic barrier of elementary reactions is reduced [85]. Besides, density functional theory calculations affirmed that the fabrication of vacancies can effectively accelerate charge transfer and improve the inherent catalytic activity of BP, which is important for designing BP with high electrocatalytic activity (Fig. 6f) [86].

    3.2.3   Transition-metal dichalcogenides (TMDs)

    As binary analogues to graphene, TMDs have the general molecular formula of MX2, where M is a transition metal belonging to groups IVB to VIIIB and X is a chalcogen from group VIA (S, Se, Te). The M and the X are connected by a strong ionic bond. The crystal structure of 2D TMD consists of a X-M-X sandwich model with van der Waals interactions. TMDs have suitable aspect ratio structures and tunable layer-dependent electronic structure [87]. Through the different ways of interlayer X-M-X layer stacking, the chemical phase of MX2 can be divided into triangular (1T), the distorted 1T (1T') and hexagonal (2H) (Fig. 7a). 1T-phase TMDs possess metallic properties such as higher electrical conductivity, which is more beneficial to electrocatalytic HER. The unique phase transformation properties of TMDs open up a novel avenue to the rational design of high-efficiency electrocatalysts for HER [88].

    Figure 7

    Figure 7.  (a) Schematic structures of MoS2 with different phases of 1T, distorted 1T, 2H. Reproduced with permission [88]. Copyright 2017, American Chemical Society. (b) STM images of MoS2 nanoparticles on Au (111). Reproduced with permission [95]. Copyright 2007, American Association for the Advancement of Science. (c) Polarization curves of different phase states of MoS2 nanosheet electrodes before and after edge oxidation. Reproduced with permission [97]. Copyright 2013, American Chemical Society. (d) Schematic illustration of OH− functionality in upgrading HER on the di-anionic MoS2 interface and the probable reaction processes. Reproduced with permission [104]. Copyright 2020, Springer Nature. (e) TEM-HRTEM images and SAED patterns of different MoSe2 nanosheets. Reproduced with permission [102]. Copyright 2018, Wiley-VCH. (f) The calculated results of HER free energy and △GH* with Mo site and Se site in different cases. Reproduced with permission [111]. Copyright 2018, Wiley-VCH.
    DownLoad: Full-Size Img PowerPoint

    Molybdenum disulfides (MoS2) have been widely studied as electrocatalysts since 1970s [89], with edge sites proved to be active for HER [90]. As the development of size and morphology control of MoS2 [91-93], the Mo with 50% sulfur content was found to be the optimal edge surface [94]. HER activity showed a linear correlation with the length of edge on MoS2 catalyst. (Fig. 7b) [95]. Furthermore, studies have suggested that the HER activity is also essentially determined by the electronic structure of TMDs, which can be optimized by phase engineering, heteroatom doping, and interfacial design approaches (Fig. 7c). [96-98]. N-doped MoS2 nanosheets from a facile self-templating method have high density of active edge sites and upgraded electronic conductivity in basal plane, exhibiting outstanding HER performance with an overpotential of 114 mV to reach 10 mA/cm2 and long-term stability over 10 h in 0.5 mol/L H2SO4 [99]. Similarly, The Ni doping can effectively decrease the kinetic energy barrier of the initial step of water splitting and accelerate the desorption of the formed OH−, displaying superior HER activity in 1 mol/L KOH aqueous solution with an exceedingly low overpotential of ~98 mV at 10 mA/cm2 [100-103]. Besides, optimizing the reaction interface of MoS2 to preferentially adsorb reactants to inner Helmholtz plane is able to efficiently reduce kinetic resistance of HER. Luo et al. constructed a di-anionic MoS2 surface by OH−, which possessed controlled molecular substitution of S sites that were functioned as active sites. Furthermore, the OH− modified on the MoS2 interface endows strong non-covalent hydrogen bonding effect with the reactants (Fig. 7d) [104]. Similar studies were also noted for ReS2, VS2, RuS2, WS2 and other transition metal-dithio compounds [105-107].

    Akin to MoS2, MoSe2 has excellent HER performance [108]. The 1T-MoSe2 is better than 2H-MoSe2 because of much more predominant active area and higher conductivity [109]. Deng et al. designed a stable (1T-2H)-MoSe2 through phase modulation and Ndoping method to achieve efficient HER performance with a notably low overpotential of 137 mV at 100 mA/cm2 and a small Tafel slope of 32 mV/dec in a 0.5 mol/L H2SO4 electrolyte. The N doping can offer more electrochemical active areas, high electrical conductivity, and promote the phase transition from 2H to 1T (Fig. 7e) [102]. Chen et al. doped Co into MoSe2 to build a heterogeneous catalyst via chemical vapor deposition method. The Co dopants help to generate more distortions and defects, which consequently introduce more active sites and eventually boost the HER performance [110]. Except doping approaches, designing vacancies is also a potential strategy to increase active sites and stimulate intrinsic catalytic activity [101]. The feasibility of defect engineering has been demonstrated by introducing Se and Mo vacancies into MoSe2. The Se and Mo vacancies can regulate the electronic structure of the basal plane and edge, thereby optimizing the △GH* to nearly zero and generating more catalytic sites (Fig. 7f). Meanwhile, the Se and Mo vacancies are expected to increase the number of gap states and the density of electrons near the Fermi level, as a result of reduced kinetic barrier of HER in 0.5 mol/L H2SO4 media [111].

    3.2.4   MXenes

    MXenes in possession of excellent electrical conductivity and more catalytically active sites are potential substitutions of 2D metal-free alkene and TMDs for electrochemical HER [112]. The general formula of MXene is Mn+1XnTx, where M stands for an early transition metal, X can be C or N, and Tx is the surface functional group O, OH or F [113]. Generally, most of the MXenes are prepared from selective chemical etching of layered materials Mn+1AXn (A are main group elements such as Al) with HF, NH4HF2 or LiF/HCl mixtures [114]. WXC is predicted to have the highest catalytic activity among other Mxenes, according a calculated △GH* that is closest to 0 eV. However, this is not experimental documented because of its poor stability, high density covered F groups and unskillful preparation methods [115, 116]. The HER catalytic activity of MXenes also can be upgraded via defect engineering by adding ad-atoms or vacancies. Lind et al. studied the vacancy effect on the HER performance of W1.33C. They found that protons can transfer to the vacancies and transform to hydrogen atoms under a metastable condition at high cathodic potentials (Fig. 8a) [117]. Similarly, the Mo2TiC2Tx nanosheets with a large number of surface Mo vacancies derived from electrochemical exfoliation can improve the hydrogen absorption and desorption characteristics with low overpotentials of 30 and 77 mV at 10 and 100 mA/cm2 in a 0.5 mol/L H2SO4 media, respectively [118].

    Figure 8

    Figure 8.  (a) A landscape of relative energies of all configurations of adsorbed H on W1.33C. Copied with permission [117]. Copyright 2021, Wiley-VCH. (b) The SEM image of Ti3C2Tx nanosheets. Reproduced with permission [119]. Copyright 2019, Wiley-VCH. (c) The STEM-ADF image of an edge region in Mo2C film. Reproduced with permission [122]. Copyright 2017, Wiley-VCH. (d) The schematic structure of LDH. Copied with permission [126]. Copyright 2021, the Royal Society of Chemistry. (e) The XRD patterns of different materials. Copied with permission [127]. Copyright 2017, the Royal Society of Chemistry. (f) Schematic representation of formation of various bonds on the surface of the catalyst. Copied with permission [26]. Copyright 2011, American Association for the Advancement of Science.
    DownLoad: Full-Size Img PowerPoint

    The unique interface functional groups of MXenes are of vital importance to electrocatalysis performance. Thus, surface functionalization, such as oxidation and hydrogenation can improve the inherent activity adsorption ability of the reaction intermediates of the MXenes catalyst [115]. Jiang et al. reported the oxygenfunctionalized ultrathin packed accordion-like Ti3C2Tx nanosheets with a low overpotential of 190 mV at 10 mA/cm2 in a 0.5 mol/L H2SO4 electrolyte (Fig. 8b) [119, 120]. Besides, hydrogenated MXenes also displayed improved HER performance due to the increased density of covered H atoms on the surface of catalysts, which endowed minimized overpotential and near-zero △GH* [115].

    Furthermore, MXenes coupled with other materials can increase the number of active sites and conductivity. Xiao et al. fabricated a heterostructure of highly conductive MoSe2 and oxygen-terminated Ti3C2, as a result of accelerated charge transfer and reduced surface reaction kinetics [121]. In addition, Geng et al. fabricated a vertically large-area Mo2C/graphene integrated structure with high crystallinity and excellent electronic coupling, which can be used as a charge relay system for HER (Fig. 8c) [122]. The integration of MXenes and the atom-thin 2D electrocatalyst is beneficial to overcome the interfacial Schottky barrier, thereby increasing the catalytic activity for HER [123, 124].

    3.2.5   Layered double hydroxides (LDHs)

    The general formula of LDHs is [M1−x2+Mχ3+(OH)2]χ+ [Ap−χ/p]χ+·mH2O, where the M2+ and M3+ are bivalent and trivalent metallic cations, respectively (Fig. 8d). The An− represents an interlayer anion. X is the depiction of surface charge, which is subject to change for various applications [125-127]. Many highperformance 2D electrocatalysts are suitable in acidic media. In contrast, the LDHs have commendable adaptability in various alkaline media [128, 129]. The active areas of LDHs were usually buried inside or covered, leading to low inherent catalytic activity under alkaline environment. To solve this problem, Yang et al. fabricated vertically oriented array of noble metal-free Ni-Co LDH nanosheets doped by B, with low overpotentials of 151, 286 and 381 mV at large current densities of 100, 500 and 1000 mA/cm2 in 1 mol/L KOH solution, respectively. The improved electrocatalytic activity could be attributed to the deconstruction of the original crystalline structure, which is caused by the BO33− displacing the lattice OH− in LDH (Fig. 8e). This created more effective defects such as oxygen vacancies and unsaturated atoms, and finally increased the number of electrocatalytic active sites and enhanced its conductivity. Besides, the B dopants can raise the local electron density, advance the dissociation of absorbed H2O and transfer absorbed H onto the neighboring metal atoms to produce H2 [130]. Similarly, doping on a 2D single-layer Ni(OH)2 with platinum nanowires exhibited excellent electrocatalytic activity for HER in an alkaline solution with a low potential of −0.07 V at 2.48 mA/cm2. In this hybrid system, Ni(OH)2 substrates can effectively activate the HO–H bond, improving aqueous solubility of the catalyst (Fig. 8f) [26]. Besides, the unique 1D-2D ultrathin structure of the catalyst can expose more active areas, while improve the rate of electron transporting and lower dynamic barrier of Volmer step. The large contact area between Pt and LDH can effectively reduce any possible migration and aggregation, thus enhancing the catalytic stability [131].

    4. Conclusions and perspectives

    This comprehensive review summarized the recent advances of high-performance HER 2D electrochemical nanocatalysts. The corresponding strategies for engineering the catalytic performance are introduced. We shed light on the inherent electrochemistry arising from intrinsic elemental make-up, and upgraded performance by physical and chemical modifications, such as doping, defect, and phase engineering, as well as fabricating composites with different building blocks. Despite the significant progress has been achieved so far, the fundamental research and practical large-scale application of hydrogen energy fed by electrochemical hydrogen evolution are still in a developing stage. Many critical challenges still remain around the future landscape of this important research topic (Fig. 9).

    Figure 9

    Figure 9.  Panoramic prospects of 2D electrocatalysts for HER.
    DownLoad: Full-Size Img PowerPoint

    First, there have been significant progress and breakthrough in development of high-performance 2D electrocatalysts. It is desirable to achieve better HER catalysts superior to commercial Pt/C electrocatalyst. Despite enriching the family with more 2D electrocatalysts and modification strategies, some external field coupling could be considered, such as electric field, magnetic field, vibration and light illumination. They can adjust the intrinsic activity of the catalyst and provide additional driving forces to improve the reaction dynamics [132, 133].

    Second, many ambiguities still remain regarding the reaction mechanism of HER. Current characterizations of HER only provide the information before and after HER measurements while important information such as intrinsic structure evolution and absorbed intermediates during reaction is missing. Unfortunately, these are more essential for understanding the HER mechanism. Thus, the development of more operando characterization and high-resolution techniques to probe the active sites and the microstructure of electrocatalysts during the HER process is highly desirable to unveil the underlying catalytic mechanism, especially for hybrid 2D electrocatalyst systems.

    Third, currently used density functional calculations have been widely employed to predict HER transition states and intermediates. Most of time, it is not convincing enough to support the hypothesis implying from experimental results. Gaining insight into the mechanisms of HER is also beneficial for rationally guiding the design of high-performance catalysts. To date, the flourishment of artificial intelligence has made it possible to conduct automatic calculation and online simulation [134]. The mechanistic knowledge derived from these tools could be fed back to the active machine learning to screen the desirable candidates for experimental validation.

    Finally, the electrochemistry of 2D materials provides opportunities to discover their practical application in energy catalysis. Their capital cost and green-chemistry synthetic methods should be on the list of priorities. To expand the production from lab "hand-made" to industrial scale ones, low-cost materials and ecofriendly synthesis approches should be explored. Moreover, the electricity consumption of water electrolyzers cannot be neglected. Efficient anode materials, and alternative fine chemicals refinement reaction, coupled with these effective cathodic HER catalysts powered by the renewable electricity resource could be utilized to bloom the industrial-scale hydrogen production.

    In summary, the advance of extensive and in-depth researches on 2D materials make them a type of valuable catalyst in electrocatalytic hydrogen production. In view of their successful experience in electrocatalytic HER, the utility of 2D nanocatalysts could be extended in many other electrochemistry-related industries such as photocatalysis, batteries, semiconductors, biosensing and healthcare. The ultimate goal of sustainable development of human society will probably be achieved.

    Declaration of competing interest

    The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

    Acknowledgments

    This work was supported by the National Natural Science Foundation of China (Nos. 22075092, 21805103), the Program for HUST Academic Frontier Youth Team (No. 2018QYTD15), the Innovation and Talent Recruitment Base of New Energy Chemistry and Device (No. B21003) and the National 1000 Young Talents Program of China.


    1. [1]

      Q. Xu, J. Zhang, D. Wang, Y. Li, Chin. Chem. Lett. 32 (2021) 3771–3781. doi: 10.1016/j.cclet.2021.05.032

    2. [2]

      Y. Wang, Y. Zhao, X. Ding, L. Qiao, J. Energy Chem. 60 (2021) 451–479 doi: 10.3390/healthcare9040451

    3. [3]

      J. Chi, H. Yu, Chin. J. Catal. 39 (2018) 390–394 doi: 10.1016/S1872-2067(17)62949-8

    4. [4]

      L. Zhang, L. Zhuang, H. Liu, et al., Small Sci. 1 (2021) 2000027 doi: 10.1002/smsc.202000027

    5. [5]

      S. Li, J. Sun, J. Guan, Chin. J. Catal. 42 (2021) 511–556 doi: 10.1016/S1872-2067(20)63693-2

    6. [6]

      M. Grätzel, Nature 414 (2001) 338–344 doi: 10.1038/35104607

    7. [7]

      L. Zhang, H. Zhao, S. Xu, et al., Small Struct. 2 (2021) 2000048 doi: 10.1002/sstr.202000048

    8. [8]

      C.T. Hsieh, X.F. Chuah, C.L. Huang, et al., Small Method. 3 (2019) 1900234 doi: 10.1002/smtd.201900234

    9. [9]

      C. Chen, L. Wang, B. Zhu, et al., J. Energy Chem. 54 (2021) 528–554 doi: 10.1016/j.jechem.2020.05.068

    10. [10]

      Y. Zhang, K. Ren, L. Wang, L. Wang, Z. Fan, Chin. Chem. Lett. 33 (2022) 33–60. doi: 10.6023/cjoc202107066

    11. [11]

      H.C. Zeng, ChemCatChem 12 (2020) 5303–5311 doi: 10.1002/cctc.202001003

    12. [12]

      V. Polshettiwar, R. Luque, A. Fihri, et al., Chem. Rev. 111 (2011) 3036–3075 doi: 10.1021/cr100230z

    13. [13]

      Y. Gong, X. Xing, Y. Wang, et al., Small Sci. (2021) 2100006 doi: 10.1002/smsc.202100006

    14. [14]

      H.B. Aiyappa, J. Masa, C. Andronescu, et al., Small Method. 3 (2019) 1800415 doi: 10.1002/smtd.201800415

    15. [15]

      X. Liu, T. Yue, K. Qi, et al., Chin. Chem. Lett. 31 (2020) 2189–2201 doi: 10.1002/mma.6033

    16. [16]

      W. Liu, H. Zhang, C. Li, et al., J. Energy Chem. 47 (2020) 333–345 doi: 10.2147/nss.s248643

    17. [17]

      P. Prabhu, J.M. Lee, Chem. Soc. Rev. 50 (2021) 6700–6719 doi: 10.1039/d0cs01041c

    18. [18]

      Y. Zheng, Y. Jiao, L.H. Li, et al., ACS Nano 8 (2014) 5290–5296 doi: 10.1021/nn501434a

    19. [19]

      D. Liu, J. Wang, J. Lu, et al., Small Method. 3 (2019) 1900083 doi: 10.1002/smtd.201900083

    20. [20]

      D. Voiry, J. Yang, M. Chhowalla, Adv. Mater. 28 (2016) 6197–6206 doi: 10.1002/adma.201505597

    21. [21]

      Y. He, P. Tang, Z. Hu, et al., Nat. Commun. 11 (2020) 57 doi: 10.1038/s41467-019-13631-2

    22. [22]

      S. Intikhab, V. Natu, J. Li, et al., J. Catal. 371 (2019) 325–332 doi: 10.1016/j.jcat.2019.01.037

    23. [23]

      W. Fang, L. Huang, S. Zaman, et al., Chem. Res. Chin. Univ. 36 (2020) 611–621 doi: 10.1007/s40242-020-0182-3

    24. [24]

      A.J. Bard, Nature 368 (1994) 597–598 doi: 10.1038/368597a0

    25. [25]

      C.G. Morales-Guio, L.A. Stern, X. Hu, Chem. Soc. Rev. 43 (2014) 6555–6569 doi: 10.1039/C3CS60468C

    26. [26]

      R. Subbaraman, D. Tripkovic, D. Strmcnik, et al., Science 334 (2011) 1256 doi: 10.1126/science.1211934

    27. [27]

      Q. Gao, W. Zhang, Z. Shi, L. Yang, Y. Tang, Adv. Mater. 31 (2019) 1802880 doi: 10.1002/adma.201802880

    28. [28]

      Z.W. Seh, J. Kibsgaard, C.F. Dickens, et al., Science 355 (2017) eaad4998 doi: 10.1126/science.aad4998

    29. [29]

      B. Xiong, L. Chen, J. Shi, ACS Catal. 8 (2018) 3688–3707 doi: 10.1021/acscatal.7b04286

    30. [30]

      J. Zhu, L. Hu, P. Zhao, L.Y.S. Lee, K.Y. Wong, Chem. Rev. 120 (2020) 851–918 doi: 10.1021/acs.chemrev.9b00248

    31. [31]

      H. Vrubel, T. Moehl, M. Grätzel, X. Hu, Chem. Commun. 49 (2013) 8985–8987 doi: 10.1039/c3cc45416a

    32. [32]

      M. Zeng, Y. Li, J. Mater. Chem. A 3 (2015) 14942–14962 doi: 10.1039/C5TA02974K

    33. [33]

      J. Wang, F. Xu, H. Jin, Y. Chen, Y. Wang, Adv. Mater. 29 (2017) 1605838 doi: 10.1002/adma.201605838

    34. [34]

      A. Ali, P.K. Shen, Carbon Energy 2 (2020) 99–121 doi: 10.1002/cey2.26

    35. [35]

      S.L. Cai, W.G. Zhang, R.N. Zuckermann, et al., Adv. Mater. 27 (2015) 5762–5770 doi: 10.1002/adma.201500124

    36. [36]

      F. Yang, S. Cheng, X. Zhang, et al., Adv. Mater. 30 (2018) 1702415 doi: 10.1002/adma.201702415

    37. [37]

      M.X. Wu, Y.W. Yang, Chin. Chem. Lett. 28 (2017) 1135–1143 doi: 10.1016/j.cclet.2017.03.026

    38. [38]

      T. Sick, A.G. Hufnagel, J. Kampmann, et al., J. Am. Chem. Soc. 140 (2018) 2085–2092 doi: 10.1021/jacs.7b06081

    39. [39]

      S.Y. Ding, J. Gao, Q. Wang, et al., J. Am. Chem. Soc. 133 (2011) 19816–19822 doi: 10.1021/ja206846p

    40. [40]

      H. Sahabudeen, H. Qi, B.A. Glatz, et al., Nat. Commun. 7 (2016) 13461 doi: 10.1038/ncomms13461

    41. [41]

      H. Huang, F. Li, Y. Zhang, Y. Chen, J. Mater. Chem. A 7 (2019) 5575–5582 doi: 10.1039/c9ta00040b

    42. [42]

      B. Ball, C. Chakravarty, P. Sarkar, J. Phys. Chem. Lett. 11 (2020) 1542–1549 doi: 10.1021/acs.jpclett.9b03876

    43. [43]

      S. Maiti, A.R. Chowdhury, A.K. Das, ChemNanoMat 6 (2020) 99–106 doi: 10.1002/cnma.201900499

    44. [44]

      C. Yang, S. Tao, N. Huang, et al., ACS Appl. Nano Mater. 3 (2020) 5481–5488 doi: 10.1021/acsanm.0c00786

    45. [45]

      D. Wu, Q. Xu, J. Qian, X. Li, Y. Sun, Chem. Eur. J. 25 (2019) 3105–3111

    46. [46]

      A. Dhakshinamoorthy, A.M. Asiri, H. Garcia, Adv. Mater. 31 (2019) 1900617 doi: 10.1002/adma.201900617

    47. [47]

      X. Zhang, J. Han, J. Guo and Z. Tang, Small Struct. 2 (2021) 2000141 doi: 10.1002/sstr.202000141

    48. [48]

      X. He, F. Yin, H. Wang, B. Chen, G. Li, Chin. J. Catal. 39 (2018) 207–227 doi: 10.1016/S1872-2067(18)63017-7

    49. [49]

      X. Li, Z. Wang and L. Wang, Small Sci. 1 (2021) 2000074 doi: 10.1002/smsc.202000074

    50. [50]

      T. Xia, Y. Lin, W. Li, M. Ju, Chin. Chem. Lett. 32 (2021) 2975–2984. doi: 10.1016/j.cclet.2021.02.058

    51. [51]

      Y.P. Wu, W. Zhou, J. Zhao, et al., Angew. Chem. Int. Ed. 56 (2017) 13001–13005 doi: 10.1002/anie.201707238

    52. [52]

      L. Qi, Y.Q. Su, Z. Xu, et al., J. Mater. Chem. A 8 (2020) 22974–22982 doi: 10.1039/d0ta08094b

    53. [53]

      M. Zhao, W. Li, J. Li, W. Hu, C.M. Li, Adv. Sci. 7 (2020) 2001965 doi: 10.1002/advs.202001965

    54. [54]

      D. Zhu, J. Liu, Y. Zhao, Y. Zheng, S.Z. Qiao, Small 15 (2019) 1805511 doi: 10.1002/smll.201805511

    55. [55]

      M. Jahan, Z. Liu, K.P. Loh, Adv. Funct. Mater. 23 (2013) 5363–5372 doi: 10.1002/adfm.201300510

    56. [56]

      H. Huang, Y. Zhao, Y. Bai, et al., Adv. Sci. 7 (2020) 2000012 doi: 10.1002/advs.202000012

    57. [57]

      Y. Sun, Z. Xue, Q. Liu, et al., Nat. Commun. 12 (2021) 1369 doi: 10.1038/s41467-021-21595-5

    58. [58]

      R. Dong, Z. Zheng, D.C. Tranca, et al., Chem. Eur. J. 23 (2017) 2255–2260 doi: 10.1002/chem.201605337

    59. [59]

      Z. Chen, H. Qing, K. Zhou, D. Sun, R. Wu, Prog. Mater. Sci. 108 (2020) 100618 doi: 10.1016/j.pmatsci.2019.100618

    60. [60]

      M. Kuang, Q. Wang, P. Han, G. Zheng, Adv. Energy Mater. 7 (2017) 1700193 doi: 10.1002/aenm.201700193

    61. [61]

      G. Anandhababu, Y. Huang, D.D. Babu, M. Wu, Y. Wang, Adv. Funct. Mater. 28 (2018) 1706120 doi: 10.1002/adfm.201706120

    62. [62]

      S.M. Oh, S.B. Patil, X. Jin, S.J. Hwang, Chem. Eur. J. 24 (2018) 4757–4773 doi: 10.1002/chem.201704284

    63. [63]

      P. Karthick Kannan, P. Shankar, C. Blackman, C.H. Chung, Adv. Mater. 31 (2019) 1803432 doi: 10.1002/adma.201803432

    64. [64]

      Y. Chen, Z. Fan, Z. Zhang, et al., Chem. Rev. 118 (2018) 6409–6455 doi: 10.1021/acs.chemrev.7b00727

    65. [65]

      H. Liu, H. Tang, M. Fang, et al., Adv. Mater. 28 (2016) 8170–8176 doi: 10.1002/adma.201601180

    66. [66]

      R. Shen, J. Xie, Q. Xiang, et al., Chin. J. Catal. 40 (2019) 240–288 doi: 10.1016/S1872-2067(19)63294-8

    67. [67]

      X. Zeng, Y. Zhao, X. Hu, G.D. Stucky, M. Moskovits, Small Struct. 2 (2021) 2000138 doi: 10.1002/sstr.202000138

    68. [68]

      R. Gusmão, Z. Sofer, D. Bouša, M. Pumera, Angew. Chem. Int. Ed. 56 (2017) 14417–14422 doi: 10.1002/anie.201706389

    69. [69]

      C. Gibaja, M. Assebban, I. Torres, et al., J. Mater. Chem. A 7 (2019) 22475–22486 doi: 10.1039/c9ta06072c

    70. [70]

      C. Li, Y. Xu, S. Liu, et al., ACS Sustain. Chem. Eng. 7 (2019) 15747–15754 doi: 10.1021/acssuschemeng.9b03967

    71. [71]

      J. Fan, J. Wu, X. Cui, et al., J. Am. Chem. Soc. 142 (2020) 3645–3651 doi: 10.1021/jacs.0c00218

    72. [72]

      A. Mahmood, H. Lin, N. Xie, X. Wang, Chem. Mat. 29 (2017) 6329–6335 doi: 10.1021/acs.chemmater.7b01598

    73. [73]

      S.W. Jang, S. Dutta, A. Kumar, et al., ACS Nano 14 (2020) 10578–10588 doi: 10.1021/acsnano.0c04628

    74. [74]

      T.P. Yadav, C.F. Woellner, T. Sharifi, et al., ACS Nano 14 (2020) 7435–7443 doi: 10.1021/acsnano.0c03081

    75. [75]

      J.Q. Chi, M. Yang, Y.M. Chai, et al., J. Energy Chem. 48 (2020) 398–423 doi: 10.1016/j.jechem.2020.02.013

    76. [76]

      J. Wang, H. Zhang and X. Wang, Small Method. 1 (2017) 1700118 doi: 10.1002/smtd.201700118

    77. [77]

      K. Hu, T. Ohto, Y. Nagata, et al., Nat. Commun. 12 (2021) 203 doi: 10.1038/s41467-020-20503-7

    78. [78]

      X. Zheng, J. Xu, K. Yan, et al., Chem. Mat. 26 (2014) 2344–2353 doi: 10.1021/cm500347r

    79. [79]

      L. Li, D. Zhang, J. Deng, Y. Gou, J. Fang, J. Energy Chem. 49 (2020) 365–374 doi: 10.1016/j.jechem.2020.03.010

    80. [80]

      Y. Fujita, H.O. Venterink, P.M. Van Bodegom, et al., Nature 505 (2014) 82–86 doi: 10.1038/nature12733

    81. [81]

      J. Si, J. Yu, Y. Shen, M. Zeng, L. Fu, Small Struct. 2 (2021) 2000101 doi: 10.1002/sstr.202000101

    82. [82]

      X. Wang, L. Bai, J. Lu, et al., Angew. Chem. Int. Ed. 58 (2019) 19060–19066 doi: 10.1002/anie.201911696

    83. [83]

      Y. Li, W. Pei, J. He, et al., ACS Catal. 9 (2019) 10870–10875 doi: 10.1021/acscatal.9b03506

    84. [84]

      X. Li, L. Xiao, L. Zhou, et al., Angew. Chem. Int. Ed. 59 (2020) 21106–21113 doi: 10.1002/anie.202008514

    85. [85]

      R. He, J. Hua, A. Zhang, et al., Nano Lett. 17 (2017) 4311–4316 doi: 10.1021/acs.nanolett.7b01334

    86. [86]

      Y. Cai, J. Gao, S. Chen, et al., Chem. Mat. 31 (2019) 8948–8956 doi: 10.1021/acs.chemmater.9b03031

    87. [87]

      B. Zhao, Z. Wan, Y. Liu, et al., Nature 591 (2021) 385–390 doi: 10.1038/s41586-021-03338-0

    88. [88]

      C. Tan, X. Cao, X.J. Wu, et al., Chem. Rev. 117 (2017) 6225–6331 doi: 10.1021/acs.chemrev.6b00558

    89. [89]

      H. Tributsch, J.C. Bennett, J. Electronanal. Chem. 81 (1977) 97–111 doi: 10.1016/S0022-0728(77)80363-X

    90. [90]

      B. Hinnemann, P.G. Moses, J. Bonde, et al., J. Am. Chem. Soc. 127 (2005) 5308–5309 doi: 10.1021/ja0504690

    91. [91]

      J. Wei, G. Wang, Y. Zhang, et al., Chin. Chem. Lett. 32 (2021) 1191–1196 doi: 10.1016/j.cclet.2020.08.005

    92. [92]

      S. Hua, D. Qu, L. An, et al., Chin. J. Catal. 38 (2017)1028–1037 doi: 10.1016/S1872-2067(17)62830-4

    93. [93]

      K. Jiang, M. Luo, Z. Liu, et al., Nat. Commun. 12 (2021) 1687 doi: 10.1038/s41467-021-21956-0

    94. [94]

      H.I. Karunadasa, E. Montalvo, Y. Sun, et al., Science 335 (2012) 698 doi: 10.1126/science.1215868

    95. [95]

      T.F. Jaramillo, K.P. Jørgensen, J. Bonde, et al., Science 317 (2007) 100 doi: 10.1126/science.1141483

    96. [96]

      J. Hu, C. Zhang, Y. Zhang, et al., Small 16 (2020) 2002212 doi: 10.1002/smll.202002212

    97. [97]

      D. Voiry, M. Salehi, R. Silva, et al., Nano Lett. 13 (2013) 6222–6227 doi: 10.1021/nl403661s

    98. [98]

      E.E. Benson, H. Zhang, S.A. Schuman, et al., J. Am. Chem. Soc. 140 (2018) 441–450 doi: 10.1021/jacs.7b11242

    99. [99]

      H. Wang, X. Xiao, S. Liu, et al., J. Am. Chem. Soc. 141 (2019) 18578–18584 doi: 10.1021/jacs.9b09932

    100. [100]

      J. Zhang, T. Wang, P. Liu, et al., Energy Environ. Sci. 9 (2016) 2789–2793 doi: 10.1039/C6EE01786J

    101. [101]

      O. Lehtinen, H.P. Komsa, A. Pulkin, et al., ACS Nano 9 (2015) 3274–3283 doi: 10.1021/acsnano.5b00410

    102. [102]

      S. Deng, F. Yang, Q. Zhang, et al., Adv. Mater. 30 (2018) 1802223 doi: 10.1002/adma.201802223

    103. [103]

      Z. Luo, J. Ge, C. Liu, W. Xing, J. Energy Chem. 41 (2020) 15–19 doi: 10.1016/j.jechem.2019.03.031

    104. [104]

      Z. Luo, H. Zhang, Y. Yang, et al., Nat. Commun. 11 (2020) 1116 doi: 10.1038/s41467-020-14980-z

    105. [105]

      H. Huang, J. Zha, S. Li, C. Tan, Chin. Chem. Lett. 33 (2022) 163–176. doi: 10.1016/j.cclet.2021.06.004

    106. [106]

      Y. Zhang, D. Yao, B. Xia, et al., Small Sci. 1 (2021) 2000052 doi: 10.1002/smsc.202000052

    107. [107]

      X. Gao, B. Li, X. Sun, et al., Chin. Chem. Lett. 32 (2021) 3591–3595. doi: 10.1016/j.cclet.2021.03.053

    108. [108]

      J. Azadmanjiri, P. Kumar, V.K. Srivastava, Z. Sofer, ACS Appl. Nano Mater. 3 (2020) 3116–3143 doi: 10.1021/acsanm.0c00120

    109. [109]

      Q. Tang, D.E. Jiang, ACS Catal. 6 (2016) 4953–4961 doi: 10.1021/acscatal.6b01211

    110. [110]

      X. Chen, Y. Qiu, G. Liu, et al., J. Mater. Chem. A 5 (2017) 11357–11363 doi: 10.1039/C7TA02327H

    111. [111]

      D. Gao, B. Xia, Y. Wang, et al., Small 14 (2018) 1704150 doi: 10.1002/smll.201704150

    112. [112]

      W. Cui, Z.Y. Hu, R.R. Unocic, G. Van Tendeloo, X. Sang, Chin. Chem. Lett. 32 (2021) 339–344 doi: 10.1016/j.cclet.2020.04.024

    113. [113]

      L. Huang, L. Ding, H. Wang, Small Sci. (2021) 2100013 doi: 10.1002/smsc.202100013

    114. [114]

      K. Li, S. Zhang, Y. Li, J. Fan, K. Lv, Chin. J. Catal. 42 (2021) 3–14 doi: 10.1016/S1872-2067(20)63630-0

    115. [115]

      H. Pan, Sci. Rep. 6 (2016) 32531 doi: 10.1038/srep32531

    116. [116]

      Y. Gao, H. Zhuo, Y. Cao, et al., Chin. J. Catal. 40 (2019) 152–159 doi: 10.1016/S1872-2067(18)63197-3

    117. [117]

      H. Lind, B. Wickman, J. Halim, et al., Adv. Sustain. Syst. 5 (2021) 2000158 doi: 10.1002/adsu.202000158

    118. [118]

      J. Zhang, Y. Zhao, X. Guo, et al., Nat. Catal. 1 (2018) 985–992 doi: 10.1038/s41929-018-0195-1

    119. [119]

      Y. Jiang, T. Sun, X. Xie, et al., ChemSusChem 12 (2019) 1368–1373 doi: 10.1002/cssc.201803032

    120. [120]

      A.D. Handoko, K.D. Fredrickson, B. Anasori, et al., ACS Appl. Energy Mater. 1 (2018) 173–180 doi: 10.1021/acsaem.7b00054

    121. [121]

      W. Xiao, D. Yan, Y. Zhang, X. Yang, T. Zhang, Energy Fuels 35 (2021) 4609–4615 doi: 10.1021/acs.energyfuels.1c00123

    122. [122]

      D. Geng, X. Zhao, Z. Chen, et al., Adv. Mater. 29 (2017) 1700072 doi: 10.1002/adma.201700072

    123. [123]

      Y. Liu, H. Xiao, W.A. Goddard, J. Am. Chem. Soc. 138 (2016) 15853–15856 doi: 10.1021/jacs.6b10834

    124. [124]

      C. Cui, R. Cheng, C. Zhang, X. Wang, Chin. Chem. Lett. 31 (2020) 988–991 doi: 10.1016/j.cclet.2019.08.026

    125. [125]

      A. Han, Z. Zhang, X. Li, et al., Small Method. 4 (2020) 2000248 doi: 10.1002/smtd.202000248

    126. [126]

      P.M. Bodhankar, P.B. Sarawade, G. Singh, A. Vinu, D.S. Dhawale, J. Mater. Chem. A 9 (2021) 3180–3208 doi: 10.1039/d0ta10712c

    127. [127]

      J. Yu, Q. Wang, D. O'Hare, L. Sun, Chem. Soc. Rev. 46 (2017) 5950–5974 doi: 10.1039/C7CS00318H

    128. [128]

      Z. Cao, B. Li, L. Sun, et al., Small Method. 4 (2020) 1900343 doi: 10.1002/smtd.201900343

    129. [129]

      Y. Zhai, X. Ren, J. Yan, et al., Small Struct. 2 (2021) 2000096 doi: 10.1002/sstr.202000096

    130. [130]

      H. Yang, Z. Chen, P. Guo, B. Fei, R. Wu, Appl. Catal. B Environ. 261 (2020) 118240 doi: 10.1016/j.apcatb.2019.118240

    131. [131]

      H. Yin, S. Zhao, K. Zhao, et al., Nat. Commun. 6 (2015) 6430 doi: 10.1038/ncomms7430

    132. [132]

      C. Xia, Y. Zhou, C. He, et al., Small Sci. 1 (2021) 2100010. doi: 10.1002/smsc.202100010

    133. [133]

      L. Huang, S. Zaman, Z. Wang, et al., Acta Phys. Chim. Sin. 37 (2021) 2009035

    134. [134]

      Y. Yang, M. Wu, X. Zhu, et al., Chin. Chem. Lett. 30 (2019) 2065–2088 doi: 10.1016/j.cclet.2019.11.001

  • Figure 1  Hydrogen production by electrolysis of water splitting.

    下载: 全尺寸图片 幻灯片

    Figure 2  Mechanism of HER on the surface of 2D materials in (a) acidic and (b) alkaline media.

    下载: 全尺寸图片 幻灯片

    Figure 3  (a) A volcano plot of experimentally measured exchange current density as a function of △GH*. Reproduced with permission [25]. Copyright 2014, the Royal Society of Chemistry. (b) Schematic illustration of the HER energetics. Reproduced with permission [27]. Copyright 2019, Wiley-VCH. (c) Schematic HER polarization curves on different electrocatalysts. Reproduced with permission [27]. Copyright 2019, Wiley-VCH.

    下载: 全尺寸图片 幻灯片

    Figure 4  (a) The TEM images of Co-COF and COF. Reproduced with permission [41]. Copyright 2019, the Royal Society of Chemistry. (b) Volcano plot of the average △GH* values of different catalysts. Copied with permission [42]. Copyright 2020, American Chemical Society (c) Impedance curves of the COF and Ru@COF. Copied with permission [43]. Copyright 2020, Wiley-VCH. (d) The structure of the MOF composing of CoO6 octahedra coordinated in a plane to ligands. Reproduced with permission [46]. Copyright 2019, Wiley-VCH. (e) The catalysis mechanism of HER in alkaline solution on the Co-MOF/MoS2 nanosheets. Copied with permission [54]. Copyright 2019, Wiley-VCH. (f) The charge density of Ni-BDC and NiRu0.13-BDC. Reproduced with permission [57]. Copyright 2021, Springer Nature.

    下载: 全尺寸图片 幻灯片

    Figure 5  (a) Schematic showing of the fabrication of metal nanosheets. Copied with permission [65]. Copyright 2016, Wiley-VCH. (b) HER polarization curves for different catalysts. Copied with permission [70]. Copyright 2019, American Chemical Society. (c) The formation enthalpies values of RhPd and RhPd-H. Reproduced with permission [71]. Copyright 2020, American Chemical Society. (d) The HRTEM image of PtAgCo nanosheets. Reproduced with permission [72]. Copyright 2017, American Chemical Society. (e) Schematic representation for 2D-Pt on LDH synthesis and its application. Copied with permission [73]. Copyright 2020, American Chemical Society. (f) 2D suspended 10-fold material with quantities of defects in difference. Reproduced with permission [74]. Copyright 2019, American Chemical Society.

    下载: 全尺寸图片 幻灯片

    Figure 6  (a) Calculation of △GH* values for N- and/or P-doped graphene. Reproduced with permission [18]. Copyright 2014, American Chemical Society. (b) Probable HER mechanisms for graphene-covered metal catalysts. Copied with permission [77]. Copyright 2021, Springer Nature. (c) The atomic structures of H2O, H–OH, HO, and the corresponding adsorption free energies of different catalysts. Reproduced with permission [83]. Copyright 2019, American Chemical Society. (d) In-situ HR-TEM images of CoFeO@BP during HER. Copied with permission [84]. Copyright 2020, Wiley-VCH. (e) TEM image of a typical MoS2-BP nanosheet. Reproduced with permission [85]. Copyright 2017, American Chemical Society. (f) Charge transfer which induces a bound donor-defect complex between hydrogen and armchair edge. Reproduced with permission [86]. Copyright 2019, American Chemical Society.

    下载: 全尺寸图片 幻灯片

    Figure 7  (a) Schematic structures of MoS2 with different phases of 1T, distorted 1T, 2H. Reproduced with permission [88]. Copyright 2017, American Chemical Society. (b) STM images of MoS2 nanoparticles on Au (111). Reproduced with permission [95]. Copyright 2007, American Association for the Advancement of Science. (c) Polarization curves of different phase states of MoS2 nanosheet electrodes before and after edge oxidation. Reproduced with permission [97]. Copyright 2013, American Chemical Society. (d) Schematic illustration of OH− functionality in upgrading HER on the di-anionic MoS2 interface and the probable reaction processes. Reproduced with permission [104]. Copyright 2020, Springer Nature. (e) TEM-HRTEM images and SAED patterns of different MoSe2 nanosheets. Reproduced with permission [102]. Copyright 2018, Wiley-VCH. (f) The calculated results of HER free energy and △GH* with Mo site and Se site in different cases. Reproduced with permission [111]. Copyright 2018, Wiley-VCH.

    下载: 全尺寸图片 幻灯片

    Figure 8  (a) A landscape of relative energies of all configurations of adsorbed H on W1.33C. Copied with permission [117]. Copyright 2021, Wiley-VCH. (b) The SEM image of Ti3C2Tx nanosheets. Reproduced with permission [119]. Copyright 2019, Wiley-VCH. (c) The STEM-ADF image of an edge region in Mo2C film. Reproduced with permission [122]. Copyright 2017, Wiley-VCH. (d) The schematic structure of LDH. Copied with permission [126]. Copyright 2021, the Royal Society of Chemistry. (e) The XRD patterns of different materials. Copied with permission [127]. Copyright 2017, the Royal Society of Chemistry. (f) Schematic representation of formation of various bonds on the surface of the catalyst. Copied with permission [26]. Copyright 2011, American Association for the Advancement of Science.

    下载: 全尺寸图片 幻灯片

    Figure 9  Panoramic prospects of 2D electrocatalysts for HER.

    下载: 全尺寸图片 幻灯片
  • 加载中
WeChat 扫一扫看文章
计量
  • PDF下载量:  0
  • 文章访问数:  854
  • HTML全文浏览量:  143
文章相关
  • 发布日期:  2022-04-15
  • 收稿日期:  2021-06-25
  • 接受日期:  2021-09-08
  • 修回日期:  2021-07-24
  • 网络出版日期:  2021-09-13
通讯作者: 陈斌, bchen63@163.com
  • 1. 

    沈阳化工大学材料科学与工程学院 沈阳 110142

  1. 本站搜索
  2. 百度学术搜索
  3. 万方数据库搜索
  4. CNKI搜索

/

返回文章

All Rights Reserved by the Chinese Chemical Society   中国化学会 版权所有 京ICP备05002797号

本系统由北京仁和汇智信息技术有限公司开发    技术支持: info@rhhz.net