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2023 Volume 42 Issue 10
2023, 42(10): 100089
doi: 10.1016/j.cjsc.2023.100089
Abstract:
In the carbon dioxide reduction reaction (CO2RR), the activity of transition metal center depends largely on its electronic structure, since the electronic rich region enhances the adsorption of intermediates at active sites, thus improving the selectivity to reduction products. In this work, we prepared CuPc/DG composite (CuPc: copper phthalocyanine; DG: defective graphene) to achieve selective CO2-to-formic acid (HCOOH) electrochemical conversion through modulating the electronic structure of Cu active centers with DG via π-π stacking. Evaluated as the electrocatalyst, the CuPc/DG composite displays a high faradaic efficiency (FE) of 44.6% 0.78 V vs. RHE for CO2RR to HCOOH. Partial current density is 5.28 mA cm-2 for HCOOH together with an exceptional stability throughout at least 20 h of reaction. On the basis of density functional theory (DFT) calculation results, defects in DG can effectively promote the charge redistribution of dispersed CuPc, where electrons transfer to CuPc from defects, forming rich electronic environment around Cu sites. The abundance of electrons makes the d-band center of Cu approach to the Fermi level and decrease the energy barrier of CuPc/DG composite for the intermediate of *OCHO, thus accelerating the reduction of CO2 to HCOOH.
In the carbon dioxide reduction reaction (CO2RR), the activity of transition metal center depends largely on its electronic structure, since the electronic rich region enhances the adsorption of intermediates at active sites, thus improving the selectivity to reduction products. In this work, we prepared CuPc/DG composite (CuPc: copper phthalocyanine; DG: defective graphene) to achieve selective CO2-to-formic acid (HCOOH) electrochemical conversion through modulating the electronic structure of Cu active centers with DG via π-π stacking. Evaluated as the electrocatalyst, the CuPc/DG composite displays a high faradaic efficiency (FE) of 44.6% 0.78 V vs. RHE for CO2RR to HCOOH. Partial current density is 5.28 mA cm-2 for HCOOH together with an exceptional stability throughout at least 20 h of reaction. On the basis of density functional theory (DFT) calculation results, defects in DG can effectively promote the charge redistribution of dispersed CuPc, where electrons transfer to CuPc from defects, forming rich electronic environment around Cu sites. The abundance of electrons makes the d-band center of Cu approach to the Fermi level and decrease the energy barrier of CuPc/DG composite for the intermediate of *OCHO, thus accelerating the reduction of CO2 to HCOOH.
2023, 42(10): 100096
doi: 10.1016/j.cjsc.2023.100096
Abstract:
Decoration of metal-organic framework (MOF) has been considered as an effective route to improve the photoelectrochemical (PEC) performance of TiO2, but there is still a lack of understanding of the regulatory structure. Herein, Ni-MOF was rationally introduced by in-situ etching method, which helps for artificially regulating the coordination state of Ni sites. The photocurrent density (0.81 mA/cm2) and IPCE value (33.1%) of TiO2-MOF-2 are about twice higher than that of pristine TiO2 due to the rich unsaturated sites of Ni-MOF. Meanwhile, the saturated coordination has caused the decline of PEC performance because of the obvious steric hindrance. Therefore, this work presents an insight for the effect of coordination state on PEC activity especially in MOF system.
Decoration of metal-organic framework (MOF) has been considered as an effective route to improve the photoelectrochemical (PEC) performance of TiO2, but there is still a lack of understanding of the regulatory structure. Herein, Ni-MOF was rationally introduced by in-situ etching method, which helps for artificially regulating the coordination state of Ni sites. The photocurrent density (0.81 mA/cm2) and IPCE value (33.1%) of TiO2-MOF-2 are about twice higher than that of pristine TiO2 due to the rich unsaturated sites of Ni-MOF. Meanwhile, the saturated coordination has caused the decline of PEC performance because of the obvious steric hindrance. Therefore, this work presents an insight for the effect of coordination state on PEC activity especially in MOF system.
2023, 42(10): 100097
doi: 10.1016/j.cjsc.2023.100097
Abstract:
The slow oxygen reduction process at the cathode and the scarcity of platinum-based metals lead to limited applications in fuel cells and metal-air cells. Recently, transition metal and nitrogen co-doped carbon-based catalysts (M–N–C) are regarded as the most prospective non-precious metal catalysts for future fuel cell applications. It is verified theoretically and experimentally that the metal and nitrogen coordination structure is the main catalytic activity center of oxygen reduction reaction (ORR), so constructing M–N–C materials with high available surface area and structural stability is an effective way to accelerate ORR. Herein, we deliberately synthesize a one-dimensional ZIF structure to fabricate one-dimensional porous Fe–N–C nanostick via two-step pyrolysis. Excitingly, the as-synthesized exhibited an outstanding ORR activity in alkaline medium (E1/2 of 0.928 V), as well as superior stability (only changed 7 mV after 10,000 cycles in alkaline medium). Our results show that the reduction of electrocatalyst dimensionality can promote mass transport and increase the accessibility of active sites, thus optimizing their performance in ORR. This work is a good demonstration of the importance of a rational design of catalyst structure for efficient ORR.
The slow oxygen reduction process at the cathode and the scarcity of platinum-based metals lead to limited applications in fuel cells and metal-air cells. Recently, transition metal and nitrogen co-doped carbon-based catalysts (M–N–C) are regarded as the most prospective non-precious metal catalysts for future fuel cell applications. It is verified theoretically and experimentally that the metal and nitrogen coordination structure is the main catalytic activity center of oxygen reduction reaction (ORR), so constructing M–N–C materials with high available surface area and structural stability is an effective way to accelerate ORR. Herein, we deliberately synthesize a one-dimensional ZIF structure to fabricate one-dimensional porous Fe–N–C nanostick via two-step pyrolysis. Excitingly, the as-synthesized exhibited an outstanding ORR activity in alkaline medium (E1/2 of 0.928 V), as well as superior stability (only changed 7 mV after 10,000 cycles in alkaline medium). Our results show that the reduction of electrocatalyst dimensionality can promote mass transport and increase the accessibility of active sites, thus optimizing their performance in ORR. This work is a good demonstration of the importance of a rational design of catalyst structure for efficient ORR.
2023, 42(10): 100104
doi: 10.1016/j.cjsc.2023.100104
Abstract:
Construction of highly active and stable bifunctional catalysts for 5 hydroxymethylfurfural oxidation reaction (HMFOR) and hydrogen evolution reaction (HER) is meaningful but remains a challenge. Herein, the NiCo–Mo2N heterostructure nanosheets catalyst with excellent HMFOR/HER performance is obtained by a simple hydrothermal and calcination method. The heterogeneous interface between NiCo and Mo2N induces electron redistribution, regulating the electronic structure of the catalyst and thus optimizing the adsorption/desorption behavior of HMFOR/HER intermediates. Consequently, NiCo–Mo2N/NF exhibits superior catalytic activity with a potential of 1.14 VRHE/ 17 mVRHE (HMFOR/HER) at 10 mA cm–2, and the HMF conversion rate, FDCA yield, and Faradaic efficiency (FE) are ~100%, 99.98%, and 98.65%, respectively. Besides, it only requires a low voltage of 1.36 V to achieve 100 mA cm–2 for HMFOR-assisted H2 production. This study provides a strategy for the development of efficient bifunctional catalysts for sustainable production of high value-added products and hydrogen.
Construction of highly active and stable bifunctional catalysts for 5 hydroxymethylfurfural oxidation reaction (HMFOR) and hydrogen evolution reaction (HER) is meaningful but remains a challenge. Herein, the NiCo–Mo2N heterostructure nanosheets catalyst with excellent HMFOR/HER performance is obtained by a simple hydrothermal and calcination method. The heterogeneous interface between NiCo and Mo2N induces electron redistribution, regulating the electronic structure of the catalyst and thus optimizing the adsorption/desorption behavior of HMFOR/HER intermediates. Consequently, NiCo–Mo2N/NF exhibits superior catalytic activity with a potential of 1.14 VRHE/ 17 mVRHE (HMFOR/HER) at 10 mA cm–2, and the HMF conversion rate, FDCA yield, and Faradaic efficiency (FE) are ~100%, 99.98%, and 98.65%, respectively. Besides, it only requires a low voltage of 1.36 V to achieve 100 mA cm–2 for HMFOR-assisted H2 production. This study provides a strategy for the development of efficient bifunctional catalysts for sustainable production of high value-added products and hydrogen.
2023, 42(10): 100136
doi: 10.1016/j.cjsc.2023.100136
Abstract:
Methanol-assisted water-splitting reaction for green hydrogen generation is more competitive to the traditional water electrolysis driven by sustainable energies due to the largely reduced energy costs. Increasing attention currently is directed to the highly efficient methanol electrooxidation catalysts that determine the catalysis efficiency, and some advanced catalysts have been developed. Given the significant advances, this review proposed a summary of the recent progress in catalysts for methanol-assisted water electrolysis. The mechanism of methanol-assisted water-splitting reaction classified by noble and non-noble metals was first presented by taking into account their distinct redox reactions. Then, the research progress of these catalysts for methanol-assisted water-splitting reactions is summarized and discussed, and the challenges and problems associated with catalyst design and optimization as well as their practical application were finally commented on. This review would be a valuable reference for catalyst development and mechanism understanding in methanol-assisted water splitting reactions for hydrogen generation.
Methanol-assisted water-splitting reaction for green hydrogen generation is more competitive to the traditional water electrolysis driven by sustainable energies due to the largely reduced energy costs. Increasing attention currently is directed to the highly efficient methanol electrooxidation catalysts that determine the catalysis efficiency, and some advanced catalysts have been developed. Given the significant advances, this review proposed a summary of the recent progress in catalysts for methanol-assisted water electrolysis. The mechanism of methanol-assisted water-splitting reaction classified by noble and non-noble metals was first presented by taking into account their distinct redox reactions. Then, the research progress of these catalysts for methanol-assisted water-splitting reactions is summarized and discussed, and the challenges and problems associated with catalyst design and optimization as well as their practical application were finally commented on. This review would be a valuable reference for catalyst development and mechanism understanding in methanol-assisted water splitting reactions for hydrogen generation.
2023, 42(10): 100158
doi: 10.1016/j.cjsc.2023.100158
Abstract:
2023, 42(10): 100159
doi: 10.1016/j.cjsc.2023.100159
Abstract:
MXenes with metal nanoparticles (NPs) immobilized on their surface are greatly desired for high-performance electrocatalysts, while the homogeneous nucleation and growth of NPs are still challenging. Herein, a new method has been proposed for uniformly anchoring Ni NPs on the altered surficial MXene. The pre-vacuum treatment on Mo2TiC2Tx (oMX) not only removes the surficial terminal groups but also induces surface oxidation defects. Meanwhile, the nucleation and growth behaviors of Ni NPs on the oMX are altered in the hydrothermal reaction, which results in a grain-size reduction of more than 50% as well as homogeneous coverage. Eventually, the oxidized surface contributes a strong coupling between oMX and Ni NPs via Ni O binging, which endows the Ni@oMX hybrid with the lowest overpotential and high durability over 75 h in 1 M KOH solution for electrocatalytic hydrogen evolution reaction (HER).
MXenes with metal nanoparticles (NPs) immobilized on their surface are greatly desired for high-performance electrocatalysts, while the homogeneous nucleation and growth of NPs are still challenging. Herein, a new method has been proposed for uniformly anchoring Ni NPs on the altered surficial MXene. The pre-vacuum treatment on Mo2TiC2Tx (oMX) not only removes the surficial terminal groups but also induces surface oxidation defects. Meanwhile, the nucleation and growth behaviors of Ni NPs on the oMX are altered in the hydrothermal reaction, which results in a grain-size reduction of more than 50% as well as homogeneous coverage. Eventually, the oxidized surface contributes a strong coupling between oMX and Ni NPs via Ni O binging, which endows the Ni@oMX hybrid with the lowest overpotential and high durability over 75 h in 1 M KOH solution for electrocatalytic hydrogen evolution reaction (HER).
2023, 42(10): 100167
doi: 10.1016/j.cjsc.2023.100167
Abstract:
Li-ion batteries (LIBs) have gained wide recognition as effective energy storage devices and power supply sources due to their exceptional volumetric energy density, mass energy density and cycling performance. The cathode materials, a key component of LIBs, play a crucial role in determining the electrochemical performance of these batteries. Therefore, there is an increasing demand to explore and investigate suitable high-energy electrode materials that can provide greater capacity and output voltage for the next generation of LIBs. This paper aims to provide a comprehensive overview of the latest researches on five typical high-voltage cathode materials. Specifically, this review will focus on the detailed analysis of their crystalline structures, reaction mechanisms during cycling, current research status and strategies aimed at improving or enhancing their overall electrochemical performance. Overall, the insights presented in this review will help researchers design and develop high-energy cathode materials with improved performance for the next generation of LIBs.
Li-ion batteries (LIBs) have gained wide recognition as effective energy storage devices and power supply sources due to their exceptional volumetric energy density, mass energy density and cycling performance. The cathode materials, a key component of LIBs, play a crucial role in determining the electrochemical performance of these batteries. Therefore, there is an increasing demand to explore and investigate suitable high-energy electrode materials that can provide greater capacity and output voltage for the next generation of LIBs. This paper aims to provide a comprehensive overview of the latest researches on five typical high-voltage cathode materials. Specifically, this review will focus on the detailed analysis of their crystalline structures, reaction mechanisms during cycling, current research status and strategies aimed at improving or enhancing their overall electrochemical performance. Overall, the insights presented in this review will help researchers design and develop high-energy cathode materials with improved performance for the next generation of LIBs.
2023, 42(10): 100168
doi: 10.1016/j.cjsc.2023.100168
Abstract:
Tuning strong metal-support interaction between Pt-based alloys and metal oxides is an effective strategy for modulating the performance of oxygen reduction reaction (ORR). Herein, Pt3Ni alloy anchored on WOx with different content of oxygen vacancies is synthesized, and the effect of unsaturated WOx on ORR activity/stability is revealed. Electrochemical results indicate that ORR activity is positively correlated with oxygen vacancy concentration, while durability presents the opposite trend. Density functional theory (DFT) calculation results suggest that controlling the content of oxygen vacancies can usefully adjust the charge redistribution between Pt3Ni and WOx, which can optimize the adsorption/activation of reactants, thus obtaining good ORR activity. This study uncovers the effect of unsaturated WOx on ORR performance for Pt-based alloys and provides a promising strategy to design efficient and stable ORR catalysts.
Tuning strong metal-support interaction between Pt-based alloys and metal oxides is an effective strategy for modulating the performance of oxygen reduction reaction (ORR). Herein, Pt3Ni alloy anchored on WOx with different content of oxygen vacancies is synthesized, and the effect of unsaturated WOx on ORR activity/stability is revealed. Electrochemical results indicate that ORR activity is positively correlated with oxygen vacancy concentration, while durability presents the opposite trend. Density functional theory (DFT) calculation results suggest that controlling the content of oxygen vacancies can usefully adjust the charge redistribution between Pt3Ni and WOx, which can optimize the adsorption/activation of reactants, thus obtaining good ORR activity. This study uncovers the effect of unsaturated WOx on ORR performance for Pt-based alloys and provides a promising strategy to design efficient and stable ORR catalysts.
