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2024 Volume 40 Issue 7
2024, 40(7): 230602
doi: 10.3866/PKU.WHXB202306029
Abstract:
Nanoscale metallic catalysts are garnering increased attention in the advancement of electrochemical energy conversion technologies. The precise control of nanocrystal morphology, size, and crystalline structures offers the ability to manipulate electronic properties and enhance intrinsic catalytic performance. Consequently, a profound understanding of the nanocrystal growth mechanism becomes imperative for the design and production of highly active catalysts. However, mechanism studies in colloidal methods generally depend on operando technics and the development is hindered by expensive cost and limited resources. And high-temperature or high-pressure reaction conditions always bring trouble for the application of the equipment, so the in situ methods have been widely used. While ex situ methods need to detach the samples from the reaction environment, which might lose information about the process and thus fail to reflect the real situation. Furthermore, in conventional methods, the use of macromolecular organics to regulate crystal morphology results in intricate post-treatment processes, and any residual substances can adversely affect catalyst performance. Electrochemical synthesis offers a clean and controllable protocol for producing metallic nanocrystals and supported heterogeneous nanoparticle catalysts. In this review, building upon the classic principles of crystal growth in chemical colloidal methods and electrodeposition, it is proposed that the processes occurring during crystal formation could be visualized or monitored through electrochemical tests. By fine-tuning electrochemical parameters and refining deposition procedures, nucleation density and growth rates along specific facet orientations of nanocrystals can be precisely managed. Electrochemical signals provide insights into in-situ reduction and deposition behaviors at the electrode-electrolyte interfaces through professional analysis. The direct loading of nanocrystals onto substrates amplifies their synergistic effects, mitigates exfoliation issues, and consequently enhances catalytic activity and stability. Additionally, due to its broader potential window compared to H2O, non-aqueous liquids hold promise as a solution for preparing active metals and alloys that exhibit distinctive catalytic performance. Furthermore, electrochemical methods facilitate the synthesis of compounds composed of metallic and nonmetal elements, including metal oxides and phosphides. Thus, electrochemical techniques are poised to offer potential high-performance nanoscale metallic catalysts along with profound insights into the crystal growth mechanism. Nevertheless, a critical challenge hindering the application of electrochemical methods lies in bridging the considerable gap between catalysts and the preparation of electrode-level catalyst layers. The electrochemical signal proves highly sensitive to variations in the reaction environment, and discrepancies in electrode and system properties can lead to distinct electrochemical responses. Consequently, thorough investigations are imperative to address these issues.
Nanoscale metallic catalysts are garnering increased attention in the advancement of electrochemical energy conversion technologies. The precise control of nanocrystal morphology, size, and crystalline structures offers the ability to manipulate electronic properties and enhance intrinsic catalytic performance. Consequently, a profound understanding of the nanocrystal growth mechanism becomes imperative for the design and production of highly active catalysts. However, mechanism studies in colloidal methods generally depend on operando technics and the development is hindered by expensive cost and limited resources. And high-temperature or high-pressure reaction conditions always bring trouble for the application of the equipment, so the in situ methods have been widely used. While ex situ methods need to detach the samples from the reaction environment, which might lose information about the process and thus fail to reflect the real situation. Furthermore, in conventional methods, the use of macromolecular organics to regulate crystal morphology results in intricate post-treatment processes, and any residual substances can adversely affect catalyst performance. Electrochemical synthesis offers a clean and controllable protocol for producing metallic nanocrystals and supported heterogeneous nanoparticle catalysts. In this review, building upon the classic principles of crystal growth in chemical colloidal methods and electrodeposition, it is proposed that the processes occurring during crystal formation could be visualized or monitored through electrochemical tests. By fine-tuning electrochemical parameters and refining deposition procedures, nucleation density and growth rates along specific facet orientations of nanocrystals can be precisely managed. Electrochemical signals provide insights into in-situ reduction and deposition behaviors at the electrode-electrolyte interfaces through professional analysis. The direct loading of nanocrystals onto substrates amplifies their synergistic effects, mitigates exfoliation issues, and consequently enhances catalytic activity and stability. Additionally, due to its broader potential window compared to H2O, non-aqueous liquids hold promise as a solution for preparing active metals and alloys that exhibit distinctive catalytic performance. Furthermore, electrochemical methods facilitate the synthesis of compounds composed of metallic and nonmetal elements, including metal oxides and phosphides. Thus, electrochemical techniques are poised to offer potential high-performance nanoscale metallic catalysts along with profound insights into the crystal growth mechanism. Nevertheless, a critical challenge hindering the application of electrochemical methods lies in bridging the considerable gap between catalysts and the preparation of electrode-level catalyst layers. The electrochemical signal proves highly sensitive to variations in the reaction environment, and discrepancies in electrode and system properties can lead to distinct electrochemical responses. Consequently, thorough investigations are imperative to address these issues.
2024, 40(7): 230505
doi: 10.3866/PKU.WHXB202305059
Abstract:
Li-O2 batteries have garnered significant attention due to their ultrahigh theoretical energy density, comparable to that of gasoline. However, despite this promise, several challenges have hindered the commercial application of Li-O2 batteries. These challenges include poor reversibility, unsatisfactory cycling duration, and high overpotential during battery operation. The key factor behind the poor reversibility of current Li-O2 batteries is the occurrence of side reactions between various battery components and discharge products or intermediates. The electrolyte, an essential component in Li-O2 batteries, plays a crucial role in charge transport and mass transfer within the battery. Among the available electrolytes used in Li-O2 batteries, liquid organic electrolytes have been predominantly investigated as potential options. However, they suffer from insufficient chemical and electrochemical stability, which contributes to the overall poor reversibility. Substantial progress has been made in understanding the factors that lead to the degradation of liquid organic electrolytes and in enhancing their stability. However, there is still a need for more significant improvements to achieve practical performance. This review comprehensively introduces the development of liquid organic electrolytes for Li-O2 batteries, focusing on solvents, lithium salts, and additives. It outlines the specific requirements of electrolytes for Li-O2 batteries and highlights the importance of reducing charge overpotentials as a critical strategy to mitigate both electrochemical and chemical degradation. The review proceeds to detail the composition of liquid organic electrolytes, beginning with solvents. Carbonates, ethers, amides, and ionic liquids are discussed, along with their respective advantages, disadvantages, and strategies to overcome limitations. The role of lithium salts is then examined, with an emphasis on the relationship between the properties of lithium salts, such as donor number and anion polarity, and electrolyte performance. Some lithium salts are highlighted for their additional functions, such as forming stable solid electrolyte interfaces (SEI) on the anode side and reducing overpotential during charging. Additives in liquid organic electrolytes are also discussed. Redox mediators and singlet oxygen quenchers are discussed as representative additives, showcasing their significance in Li-O2 batteries. Redox mediators can influence the reaction mechanism, leading to lower overpotentials in both discharge and charge processes and increased capacity. Notably, classical redox mediators like LiI are introduced, and criteria for selecting appropriate redox mediators are outlined. On the other hand, singlet oxygen quenchers convert aggressive singlet oxygen into harmless triplet oxygen, thereby suppressing unwanted side reactions in Li-O2 batteries. The mechanism behind singlet oxygen generation is also addressed. In summary, this review aims to provide a comprehensive overview of the progress in liquid organic electrolytes for Li-O2 batteries. It highlights the need for better electrolyte design by addressing various aspects such as solvents, lithium salts, and additives. This comprehensive understanding will guide future research efforts towards developing more stable and efficient electrolytes for Li-O2 batteries, thereby advancing their practical applicability.
Li-O2 batteries have garnered significant attention due to their ultrahigh theoretical energy density, comparable to that of gasoline. However, despite this promise, several challenges have hindered the commercial application of Li-O2 batteries. These challenges include poor reversibility, unsatisfactory cycling duration, and high overpotential during battery operation. The key factor behind the poor reversibility of current Li-O2 batteries is the occurrence of side reactions between various battery components and discharge products or intermediates. The electrolyte, an essential component in Li-O2 batteries, plays a crucial role in charge transport and mass transfer within the battery. Among the available electrolytes used in Li-O2 batteries, liquid organic electrolytes have been predominantly investigated as potential options. However, they suffer from insufficient chemical and electrochemical stability, which contributes to the overall poor reversibility. Substantial progress has been made in understanding the factors that lead to the degradation of liquid organic electrolytes and in enhancing their stability. However, there is still a need for more significant improvements to achieve practical performance. This review comprehensively introduces the development of liquid organic electrolytes for Li-O2 batteries, focusing on solvents, lithium salts, and additives. It outlines the specific requirements of electrolytes for Li-O2 batteries and highlights the importance of reducing charge overpotentials as a critical strategy to mitigate both electrochemical and chemical degradation. The review proceeds to detail the composition of liquid organic electrolytes, beginning with solvents. Carbonates, ethers, amides, and ionic liquids are discussed, along with their respective advantages, disadvantages, and strategies to overcome limitations. The role of lithium salts is then examined, with an emphasis on the relationship between the properties of lithium salts, such as donor number and anion polarity, and electrolyte performance. Some lithium salts are highlighted for their additional functions, such as forming stable solid electrolyte interfaces (SEI) on the anode side and reducing overpotential during charging. Additives in liquid organic electrolytes are also discussed. Redox mediators and singlet oxygen quenchers are discussed as representative additives, showcasing their significance in Li-O2 batteries. Redox mediators can influence the reaction mechanism, leading to lower overpotentials in both discharge and charge processes and increased capacity. Notably, classical redox mediators like LiI are introduced, and criteria for selecting appropriate redox mediators are outlined. On the other hand, singlet oxygen quenchers convert aggressive singlet oxygen into harmless triplet oxygen, thereby suppressing unwanted side reactions in Li-O2 batteries. The mechanism behind singlet oxygen generation is also addressed. In summary, this review aims to provide a comprehensive overview of the progress in liquid organic electrolytes for Li-O2 batteries. It highlights the need for better electrolyte design by addressing various aspects such as solvents, lithium salts, and additives. This comprehensive understanding will guide future research efforts towards developing more stable and efficient electrolytes for Li-O2 batteries, thereby advancing their practical applicability.
2024, 40(7): 230702
doi: 10.3866/PKU.WHXB202307029
Abstract:
All-solid-state batteries (ASSBs) using inorganic solid electrolytes (SEs) have emerged as crucial components in energy storage applications due to their superior safety and cycle life. In recent years, due to the extensive developments of SEs with high room temperature ionic conductivity (> 10-3 S·cm-1), the sluggish diffusion kinetics of lithium ions in SEs are no longer the primary bottleneck impeding the enhancement of ASSBs. On the contrary, the notable resistance at the cathode/SE interface has emerged as a pressing issue demanding immediate resolution. The interfacial resistances arising from various factors, including the formation of the space-charge layer, interfacial chemical reactions, and lack of intimate contact, stand as fundamental reasons for a range of performance deteriorations, such as short cycling life, low coulombic efficiency, and poor power performance. These interconnected aspects further result in differences in the orders of magnitude of the reported interfacial resistances at different fabrication temperatures and/or routes, even within the same material system. Among these factors, the solid-solid contact or chemical reaction degree is closely related to the structural and electronic properties of the selected cathode and SE materials. The observed space-charge layer effect is universal and independent of the specific components or types of ion-conductive materials. Thus, obtaining a comprehensive understanding of the physics governing the space-charge layer at the interfaces of ASSBs is pivotal for researchers to fundamentally address the high interfacial resistance stemming from it. This forms the foundation for incorporating other mechanisms (such as interfacial reactions) to more accurately quantify interfacial resistance and expedite interface research in ASSBs. In this review, we strictly derive the theoretical model of the formation of the space-charge layer caused by the inherent chemical potential difference between the cathode and SE from fundamental concepts of (electro)chemical potential and electric potential, and reveal the physical picture of its influence on interfacial resistance. Subsequently, the most recent experimental characterizations and theoretical calculations of the space-charge layer at the cathode/SE interface are comprehensively discussed. While the existence of the space-charge layer is observable through experimentation, its characterization is complicated by factors like loss of interfacial contact and interfacial reactions. Therefore, it becomes imperative to further quantify the concentration of lithium ions in the space-charge layer and its impact on interfacial resistance through theoretical calculations. However, when combining the space-charge layer model with numerical and first-principles calculations to quantitatively study interfacial resistance, accurately determining the interfacial electric potential difference at the cathode/SE interface remains challenging, resulting in several orders of magnitude difference between predicted results and experimental measurements. Consequently, grounded in the foundational physical framework of the interfacial electric potential difference, the intricate connections between this potential difference and the electronic structure of the cathode/SE interface are explored. As a result, a strategy is proposed to ascertain the interfacial electric potential difference by directly calculating the Fermi level of the cathode and SE under real bonding conditions. This endeavor is anticipated to broaden the utility of the space-charge layer model in quantitatively calculating cathode/SE interfacial resistance, offering valuable insights for optimizing the cathode/SE interface and enhancing the overall performance of ASSBs.
All-solid-state batteries (ASSBs) using inorganic solid electrolytes (SEs) have emerged as crucial components in energy storage applications due to their superior safety and cycle life. In recent years, due to the extensive developments of SEs with high room temperature ionic conductivity (> 10-3 S·cm-1), the sluggish diffusion kinetics of lithium ions in SEs are no longer the primary bottleneck impeding the enhancement of ASSBs. On the contrary, the notable resistance at the cathode/SE interface has emerged as a pressing issue demanding immediate resolution. The interfacial resistances arising from various factors, including the formation of the space-charge layer, interfacial chemical reactions, and lack of intimate contact, stand as fundamental reasons for a range of performance deteriorations, such as short cycling life, low coulombic efficiency, and poor power performance. These interconnected aspects further result in differences in the orders of magnitude of the reported interfacial resistances at different fabrication temperatures and/or routes, even within the same material system. Among these factors, the solid-solid contact or chemical reaction degree is closely related to the structural and electronic properties of the selected cathode and SE materials. The observed space-charge layer effect is universal and independent of the specific components or types of ion-conductive materials. Thus, obtaining a comprehensive understanding of the physics governing the space-charge layer at the interfaces of ASSBs is pivotal for researchers to fundamentally address the high interfacial resistance stemming from it. This forms the foundation for incorporating other mechanisms (such as interfacial reactions) to more accurately quantify interfacial resistance and expedite interface research in ASSBs. In this review, we strictly derive the theoretical model of the formation of the space-charge layer caused by the inherent chemical potential difference between the cathode and SE from fundamental concepts of (electro)chemical potential and electric potential, and reveal the physical picture of its influence on interfacial resistance. Subsequently, the most recent experimental characterizations and theoretical calculations of the space-charge layer at the cathode/SE interface are comprehensively discussed. While the existence of the space-charge layer is observable through experimentation, its characterization is complicated by factors like loss of interfacial contact and interfacial reactions. Therefore, it becomes imperative to further quantify the concentration of lithium ions in the space-charge layer and its impact on interfacial resistance through theoretical calculations. However, when combining the space-charge layer model with numerical and first-principles calculations to quantitatively study interfacial resistance, accurately determining the interfacial electric potential difference at the cathode/SE interface remains challenging, resulting in several orders of magnitude difference between predicted results and experimental measurements. Consequently, grounded in the foundational physical framework of the interfacial electric potential difference, the intricate connections between this potential difference and the electronic structure of the cathode/SE interface are explored. As a result, a strategy is proposed to ascertain the interfacial electric potential difference by directly calculating the Fermi level of the cathode and SE under real bonding conditions. This endeavor is anticipated to broaden the utility of the space-charge layer model in quantitatively calculating cathode/SE interfacial resistance, offering valuable insights for optimizing the cathode/SE interface and enhancing the overall performance of ASSBs.
2024, 40(7): 230705
doi: 10.3866/PKU.WHXB202307057
Abstract:
As for the accurate synthesis of high-performance electrochemical catalysts with good robustness, the rational design on atomic level is still a priority. Entropy, as one of the most significant thermodynamic parameters, measure the disorder of a system, which is a significant quantity for materials. The values are primarily determined by the crystal structure, magnetic moments and the atomic and electronic vibrations of the materials. According to the configurational entropy of the system, we usually divide the material into low entropy materials (LEMs) (∆Smix < 1R), medium entropy materials (MEMs) (1R ≤ ∆Smix ≥ 1.5R) and high entropy materials (HEMs) (∆Smix > 1.5R), where R is the gas molar constant. HEMs are those that consist of five or more major elements of roughly equal proportion, in a highly uniform, random manner, which typically consist of one or two major elements compared to traditional materials. As the entropy value increases, the intrinsic physical, chemical and structural properties of the material change accordingly, resulting in special physicochemical properties (e.g., strength, electrical conductivity, corrosion resistance, etc.). Moreover, due to its multi-element combination, the HEMs can be precisely regulated by selecting different elements and their ratios according to the needs, which overcomes the limitations of the traditional catalysts in terms of relatively single component, structure and field of application. Importantly, the synergistic high entropy effect and multi-component arrangement at the atomic-level interface produced by the coexistence of different metal elements in HEMs can exert higher catalytic activity, selectivity and stability in different reactions. This has attracted a lot of attention from researchers, especially in the field of electrocatalysis. In this review systematically summarizes the fundamental concepts of high-entropy catalysts (HECs), synthetic approaches (“top-down” and “bottom-up”), and the structure-performance relationships of HEMs in different types of electrocatalytic processes, mainly including hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), alcohol oxidation reaction (AOR), nitrogen reduction reaction (NRR), and carbon dioxide reduction reaction (CO2RR) etc. Thus, the advantages and potential of high-performance electrocatalysts based on entropy increase engineering are illuminate. At the same time, it is summarized and discussed that HECs are currently facing problems and challenges such as complicated material rational design, complex preparation process, the mechanism of electrocatalytic processes in which multiple metal elements interact is ambiguous, and poor stability under extreme reaction conditions. Finally, the main problems and challenges facing the current HECs research. We look forward to the future design ideas, synthesis methods different research areas and industrial applications of HECs based on entropy enhancement engineering.
As for the accurate synthesis of high-performance electrochemical catalysts with good robustness, the rational design on atomic level is still a priority. Entropy, as one of the most significant thermodynamic parameters, measure the disorder of a system, which is a significant quantity for materials. The values are primarily determined by the crystal structure, magnetic moments and the atomic and electronic vibrations of the materials. According to the configurational entropy of the system, we usually divide the material into low entropy materials (LEMs) (∆Smix < 1R), medium entropy materials (MEMs) (1R ≤ ∆Smix ≥ 1.5R) and high entropy materials (HEMs) (∆Smix > 1.5R), where R is the gas molar constant. HEMs are those that consist of five or more major elements of roughly equal proportion, in a highly uniform, random manner, which typically consist of one or two major elements compared to traditional materials. As the entropy value increases, the intrinsic physical, chemical and structural properties of the material change accordingly, resulting in special physicochemical properties (e.g., strength, electrical conductivity, corrosion resistance, etc.). Moreover, due to its multi-element combination, the HEMs can be precisely regulated by selecting different elements and their ratios according to the needs, which overcomes the limitations of the traditional catalysts in terms of relatively single component, structure and field of application. Importantly, the synergistic high entropy effect and multi-component arrangement at the atomic-level interface produced by the coexistence of different metal elements in HEMs can exert higher catalytic activity, selectivity and stability in different reactions. This has attracted a lot of attention from researchers, especially in the field of electrocatalysis. In this review systematically summarizes the fundamental concepts of high-entropy catalysts (HECs), synthetic approaches (“top-down” and “bottom-up”), and the structure-performance relationships of HEMs in different types of electrocatalytic processes, mainly including hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), alcohol oxidation reaction (AOR), nitrogen reduction reaction (NRR), and carbon dioxide reduction reaction (CO2RR) etc. Thus, the advantages and potential of high-performance electrocatalysts based on entropy increase engineering are illuminate. At the same time, it is summarized and discussed that HECs are currently facing problems and challenges such as complicated material rational design, complex preparation process, the mechanism of electrocatalytic processes in which multiple metal elements interact is ambiguous, and poor stability under extreme reaction conditions. Finally, the main problems and challenges facing the current HECs research. We look forward to the future design ideas, synthesis methods different research areas and industrial applications of HECs based on entropy enhancement engineering.
2024, 40(7): 230701
doi: 10.3866/PKU.WHXB202307019
Abstract:
Nucleophile oxidation reaction (NOR) is emerging as a significant approach for the sustainable production of value-added chemicals. Among the various types, electrocatalytic glycerol oxidation reaction (GOR) stands out as a crucial method for producing C1 to C3 chemicals including formic acid (FA). Non-noble-metal-based (oxy)hydroxides have found extensive use in GOR, yet achieving industrially-demanded current densities (> 300 mA·cm-2) at moderate potentials remains a challenge. It is well documented that GOR catalyzed by (oxy)hydroxides follows an indirect oxidation mechanism. Specifically, the nucleophile, glycerol, undergoes oxidation by the electrogenerated oxyhydroxides with electrophilic adsorption oxygen. Therefore, comprehending the evolution of the electrocatalyst in GOR is critically important. In this paper, we have developed molybdenum-doped nickel oxyhydroxides (Mo-NiOOH) through cyclic voltammetry (CV) activation of nickel molybdate (NiMoO4). We demonstrated that Mo species leach from NiMoO4, and the resulting Mo-NiOOH retains the nanosheet array morphology of NiMoO4. We subjected the freshly prepared Mo-NiOOH to systematic characterizations employing techniques such as scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) mapping, Raman spectroscopy, inductively coupled plasma-mass spectrometry (ICP-MS), and X-ray photoelectron spectroscopy (XPS). The above structural characterizations confirm that Mo-NiOOH inherits the nanosheet array morphology of the NiMoO4 precursor with reduced Mo content, thereby indicating the phase reconstruction from oxides to oxyhydroxides post CV activation. Furthermore, the Ni3+/Ni2+ ratio in Mo-NiOOH surpasses that in NiOOH derived from CV activation of Ni(OH)2. Mo-NiOOH exhibits elevated electrochemically active surface areas (ECSAs) and a higher Ni3+/Ni2+ ratio compared to NiOOH obtained through CV activation of Ni(OH)2, facilitating the Mo-NiOOH exhibits higher ratio of Ni3+/Ni2+, higher electrochemically active surface areas (ECSAs) than NiOOH, and facilitated oxidation of Ni2+ to Ni3+. Consequently, Mo-NiOOH requires a lower applied potential than NiOOH (1.51 V versus 1.84 V vs. reversible hydrogen electrode (RHE)) to achieve a high current density (400 mA·cm-2). Additionally, Mo-NiOOH demonstrates higher Faradaic efficiency towards formate (FEformate) in contrast to NiOOH (84.7% versus 59.6%), indicating enhanced carbon-carbon (C―C) bond cleavage due to Mo doping. Multi-potential step (STEP) experiments indicate that GOR catalyzed by NiOOH and Mo-NiOOH follows a similar indirect oxidation mechanism mediated by oxyhydroxides. Operando electrochemical impedance spectroscopy (EIS) and in situ Raman spectroscopy confirmed that Mo doping in NiOOH accelerates GOR kinetics and the oxidation of Ni2+ to Ni3+, contributing to the higher activity and formate selectivity of Mo-NiOOH than NiOOH. The strategy of surface modulation of oxyhydroxides through leaching of soluble anions offers guidelines for the rational design of high-performance NOR electrocatalysts.
Nucleophile oxidation reaction (NOR) is emerging as a significant approach for the sustainable production of value-added chemicals. Among the various types, electrocatalytic glycerol oxidation reaction (GOR) stands out as a crucial method for producing C1 to C3 chemicals including formic acid (FA). Non-noble-metal-based (oxy)hydroxides have found extensive use in GOR, yet achieving industrially-demanded current densities (> 300 mA·cm-2) at moderate potentials remains a challenge. It is well documented that GOR catalyzed by (oxy)hydroxides follows an indirect oxidation mechanism. Specifically, the nucleophile, glycerol, undergoes oxidation by the electrogenerated oxyhydroxides with electrophilic adsorption oxygen. Therefore, comprehending the evolution of the electrocatalyst in GOR is critically important. In this paper, we have developed molybdenum-doped nickel oxyhydroxides (Mo-NiOOH) through cyclic voltammetry (CV) activation of nickel molybdate (NiMoO4). We demonstrated that Mo species leach from NiMoO4, and the resulting Mo-NiOOH retains the nanosheet array morphology of NiMoO4. We subjected the freshly prepared Mo-NiOOH to systematic characterizations employing techniques such as scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) mapping, Raman spectroscopy, inductively coupled plasma-mass spectrometry (ICP-MS), and X-ray photoelectron spectroscopy (XPS). The above structural characterizations confirm that Mo-NiOOH inherits the nanosheet array morphology of the NiMoO4 precursor with reduced Mo content, thereby indicating the phase reconstruction from oxides to oxyhydroxides post CV activation. Furthermore, the Ni3+/Ni2+ ratio in Mo-NiOOH surpasses that in NiOOH derived from CV activation of Ni(OH)2. Mo-NiOOH exhibits elevated electrochemically active surface areas (ECSAs) and a higher Ni3+/Ni2+ ratio compared to NiOOH obtained through CV activation of Ni(OH)2, facilitating the Mo-NiOOH exhibits higher ratio of Ni3+/Ni2+, higher electrochemically active surface areas (ECSAs) than NiOOH, and facilitated oxidation of Ni2+ to Ni3+. Consequently, Mo-NiOOH requires a lower applied potential than NiOOH (1.51 V versus 1.84 V vs. reversible hydrogen electrode (RHE)) to achieve a high current density (400 mA·cm-2). Additionally, Mo-NiOOH demonstrates higher Faradaic efficiency towards formate (FEformate) in contrast to NiOOH (84.7% versus 59.6%), indicating enhanced carbon-carbon (C―C) bond cleavage due to Mo doping. Multi-potential step (STEP) experiments indicate that GOR catalyzed by NiOOH and Mo-NiOOH follows a similar indirect oxidation mechanism mediated by oxyhydroxides. Operando electrochemical impedance spectroscopy (EIS) and in situ Raman spectroscopy confirmed that Mo doping in NiOOH accelerates GOR kinetics and the oxidation of Ni2+ to Ni3+, contributing to the higher activity and formate selectivity of Mo-NiOOH than NiOOH. The strategy of surface modulation of oxyhydroxides through leaching of soluble anions offers guidelines for the rational design of high-performance NOR electrocatalysts.
2024, 40(7): 230704
doi: 10.3866/PKU.WHXB202307040
Abstract:
Metal-organic frameworks (MOFs) as efficient electrocatalysts can be employed as the promising cocatalysts in photoelectrochemistry. Herein, a strategy is developed to metal-organic frameworks as oxygen evolution cocatalyst (OEC) combined with semiconductor for improving the charge transport and reducing the bulk/surface carrier recombination. This advanced CoFe MOF/BiVO4 photoanode exhibits a photocurrent density of 4.5 mA·cm-2 at 1.23 V (vs. RHE) under AM 1.5G illumination, achieving outstanding long-term photostability. Remarkably, with the reconstruction of MOF in the long-term water oxidation reaction, more stable metal oxyhydroxides are formed on the surface of BiVO4 and the photocurrent density of the photoelectrode is further enhanced to 5 mA·cm-2. From density functional theory calculations, the enhanced photoelectrochemical (PEC) performance can be attributed to the coupling effect between Co and Fe decreasing the free energy barriers and accelerating the reaction kinetics. This work focuses on the reconfiguration of CoFe MOF catalyst to bimetallic hydroxide during long-term water oxidation. This work enables us to develop an effective pathway to design and fabricate efficient and stable photoanodes through MOFs catalysts for feasible PEC water splitting.
Metal-organic frameworks (MOFs) as efficient electrocatalysts can be employed as the promising cocatalysts in photoelectrochemistry. Herein, a strategy is developed to metal-organic frameworks as oxygen evolution cocatalyst (OEC) combined with semiconductor for improving the charge transport and reducing the bulk/surface carrier recombination. This advanced CoFe MOF/BiVO4 photoanode exhibits a photocurrent density of 4.5 mA·cm-2 at 1.23 V (vs. RHE) under AM 1.5G illumination, achieving outstanding long-term photostability. Remarkably, with the reconstruction of MOF in the long-term water oxidation reaction, more stable metal oxyhydroxides are formed on the surface of BiVO4 and the photocurrent density of the photoelectrode is further enhanced to 5 mA·cm-2. From density functional theory calculations, the enhanced photoelectrochemical (PEC) performance can be attributed to the coupling effect between Co and Fe decreasing the free energy barriers and accelerating the reaction kinetics. This work focuses on the reconfiguration of CoFe MOF catalyst to bimetallic hydroxide during long-term water oxidation. This work enables us to develop an effective pathway to design and fabricate efficient and stable photoanodes through MOFs catalysts for feasible PEC water splitting.
2024, 40(7): 230704
doi: 10.3866/PKU.WHXB202307045
Abstract:
Hexavalent chromium (Cr(VI)) may be a hazardous and non-biodegradable waste matter which will cause substantial environmental damage. Fabricating powerful photosystems to achieve efficacious elimination of Cr(VI) holds eminent promise in solving environmental issues. Thanks to their outstanding photo/electrical properties, large surface area, and customizable structure, metal-organic framework (MOF) catalysts have attracted widespread attention within the field of pollutant degradation and reduction. Nevertheless, due to the recombination of photo-generated charge carriers, pristine semiconductor MOFs’ photocatalytic performance is inadequate. To overcome this challenge, one of the most typical and effective strategies is to create heterojunctions by combining MOFs with another semiconductor. Among these strategies, the innovative step-scheme (S-scheme) heterojunction has gained increasing prominence. Unlike traditional type II and Z-scheme heterojunctions, the built-in electric field at the S-scheme heterojunction boundary enhances spatial charge separation and boosts redox capacity, thereby improving photocatalytic performance. In this study, a creative MOF-based S-scheme architecture with oxygen vacancies (OV) was built via in situ growth of MIL-101(Fe) crystals on the surface of OV-rich BiOCl microspheres. The optimized MIL-101(Fe)/BiOCl heterojunction exhibited exceptional photocatalytic performance in photo-reducing high concentrations of Cr(VI) and 88.5% of Cr(VI) solution (10 mg·L-1, 100 mL) can be removed within 60 min, which is about 4.4 and 9.0 times that of BiOCl and MIL-101(Fe). Besides, the MIL-101(Fe)/BiOCl manifests impressive practical implementation prospect due to its high anti-interference property, robustness and reusability. Photoelectron spectroscopy results validated that built-in electric field, bending band, and Coulomb attraction facilitated the transition of photoelectrons from the conduction band (CB) of BiOCl to the valence band (VB) of MIL-101(Fe), where they recombined with the photo-created holes. This suggests an S-scheme interfacial photo-carrier detachment mechanism at the MIL-101(Fe)/BiOCl interface. In addition, BET measurements indicated a notable increase in surface area with the introduction of MIL-101(Fe). The OV-rich S-scheme MIL-101(Fe)/BiOCl heterostructure boasts more reactive sites, enhanced interfacial charge separation, and optimal redox ability of photo-carriers, leading to enhanced photocatalytic properties. Measurements of active radical scavenging and electron spin resonance (ESR) confirm that e- and ·O2- are the primary active species during photocatalysis. These discoveries would open up new avenues for developing defective semiconductor/MOF S-scheme photocatalyst for environmental purification.
Hexavalent chromium (Cr(VI)) may be a hazardous and non-biodegradable waste matter which will cause substantial environmental damage. Fabricating powerful photosystems to achieve efficacious elimination of Cr(VI) holds eminent promise in solving environmental issues. Thanks to their outstanding photo/electrical properties, large surface area, and customizable structure, metal-organic framework (MOF) catalysts have attracted widespread attention within the field of pollutant degradation and reduction. Nevertheless, due to the recombination of photo-generated charge carriers, pristine semiconductor MOFs’ photocatalytic performance is inadequate. To overcome this challenge, one of the most typical and effective strategies is to create heterojunctions by combining MOFs with another semiconductor. Among these strategies, the innovative step-scheme (S-scheme) heterojunction has gained increasing prominence. Unlike traditional type II and Z-scheme heterojunctions, the built-in electric field at the S-scheme heterojunction boundary enhances spatial charge separation and boosts redox capacity, thereby improving photocatalytic performance. In this study, a creative MOF-based S-scheme architecture with oxygen vacancies (OV) was built via in situ growth of MIL-101(Fe) crystals on the surface of OV-rich BiOCl microspheres. The optimized MIL-101(Fe)/BiOCl heterojunction exhibited exceptional photocatalytic performance in photo-reducing high concentrations of Cr(VI) and 88.5% of Cr(VI) solution (10 mg·L-1, 100 mL) can be removed within 60 min, which is about 4.4 and 9.0 times that of BiOCl and MIL-101(Fe). Besides, the MIL-101(Fe)/BiOCl manifests impressive practical implementation prospect due to its high anti-interference property, robustness and reusability. Photoelectron spectroscopy results validated that built-in electric field, bending band, and Coulomb attraction facilitated the transition of photoelectrons from the conduction band (CB) of BiOCl to the valence band (VB) of MIL-101(Fe), where they recombined with the photo-created holes. This suggests an S-scheme interfacial photo-carrier detachment mechanism at the MIL-101(Fe)/BiOCl interface. In addition, BET measurements indicated a notable increase in surface area with the introduction of MIL-101(Fe). The OV-rich S-scheme MIL-101(Fe)/BiOCl heterostructure boasts more reactive sites, enhanced interfacial charge separation, and optimal redox ability of photo-carriers, leading to enhanced photocatalytic properties. Measurements of active radical scavenging and electron spin resonance (ESR) confirm that e- and ·O2- are the primary active species during photocatalysis. These discoveries would open up new avenues for developing defective semiconductor/MOF S-scheme photocatalyst for environmental purification.
2024, 40(7): 230604
doi: 10.3866/PKU.WHXB202306041
Abstract:
The continuous increase in the consumption of coal, oil, and natural gas has not only led to the depletion of unsustainable energy sources, but has also caused excessive CO2 emissions, thus resulting in serious energy crises and climate issues. In such a scenario, it is imperative to explore clean and sustainable energy conversion technologies to address the escalating energy demands and environmental crises. Photocatalytic CO2 conversion, inspired by natural photosynthesis, utilizes solar energy to convert CO2 and water into valuable chemicals. After decades of development, artificial photosynthesis has emerged as a green, cost-effective, and sustainable approach to achieving carbon neutrality. However, the challenges of low carrier separation efficiency and insufficient active sites in photocatalysts remain significant hurdles in achieving high-performance CO2 photoreduction. To address this challenge, the integration of metal nanoparticles with semiconductors to create an Ohmic junction can enhance electron-hole migration by the assist of interfacial electric field (IEF). In this study, an Ohmic junction photocatalyst is constructed by in situ formation of Bi nanoparticles on the surface of BiOCl nanosheets through a solvothermal process. The composition and morphology of the photocatalysts were analyzed using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS) was employed to assess the light absorption performance of the photocatalyst. Transient photocurrent response, electrochemical impedance spectroscopy (EIS), and electron spin resonance (ESR) were utilized to evaluate the efficiency of electron-hole transfer. The distinct work function difference between Bi nanoparticles and BiOCl nanosheets leads to favorable charge transfer characteristics within the formed Ohmic junction, significantly improving the utilization efficiency of photogenerated carriers. Besides, the Bi nanoparticles serve as co-catalysts, enhancing the activation of inert CO2. As a result, the optimized Bi/BiOCl composite (Bi/BiOCl-2) exhibits enhanced generation rates of CO (34.31 µmol·g-1) and CH4 (1.57 µmol g-1) during 4-h of irradiation, which is 2.55 and 4.76 times compared to pristine BiOCl nanosheets, respectively. Isotope tracer experiments suggest that the obtained carbon-based products are generated through CO2 photoreduction in the presence of water molecule under irradiation. Moreover, in situ Fourier-transform infrared spectroscopy (in situ FTIR) results indicate the formation of *CHO, *CH3O, b-CO32-, m-CO32-, HCO-3, HCOOH, *COOH, and HCOO- species during the CO2 reduction process and a possible mechanism for CO2 photoreduction into CO and CH4 is proposed based on these findings. After 25-h of CO2 photoreduction reaction, the yields of CO and CH4 continue to increase. Furthermore, the stability of the prepared material is confirmed by XRD pattern, XPS analysis, and TEM image. These outcomes underscore an effective strategy for constructing advanced photocatalysts tailored for high-performance solar-driven CO2 reduction.
The continuous increase in the consumption of coal, oil, and natural gas has not only led to the depletion of unsustainable energy sources, but has also caused excessive CO2 emissions, thus resulting in serious energy crises and climate issues. In such a scenario, it is imperative to explore clean and sustainable energy conversion technologies to address the escalating energy demands and environmental crises. Photocatalytic CO2 conversion, inspired by natural photosynthesis, utilizes solar energy to convert CO2 and water into valuable chemicals. After decades of development, artificial photosynthesis has emerged as a green, cost-effective, and sustainable approach to achieving carbon neutrality. However, the challenges of low carrier separation efficiency and insufficient active sites in photocatalysts remain significant hurdles in achieving high-performance CO2 photoreduction. To address this challenge, the integration of metal nanoparticles with semiconductors to create an Ohmic junction can enhance electron-hole migration by the assist of interfacial electric field (IEF). In this study, an Ohmic junction photocatalyst is constructed by in situ formation of Bi nanoparticles on the surface of BiOCl nanosheets through a solvothermal process. The composition and morphology of the photocatalysts were analyzed using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS) was employed to assess the light absorption performance of the photocatalyst. Transient photocurrent response, electrochemical impedance spectroscopy (EIS), and electron spin resonance (ESR) were utilized to evaluate the efficiency of electron-hole transfer. The distinct work function difference between Bi nanoparticles and BiOCl nanosheets leads to favorable charge transfer characteristics within the formed Ohmic junction, significantly improving the utilization efficiency of photogenerated carriers. Besides, the Bi nanoparticles serve as co-catalysts, enhancing the activation of inert CO2. As a result, the optimized Bi/BiOCl composite (Bi/BiOCl-2) exhibits enhanced generation rates of CO (34.31 µmol·g-1) and CH4 (1.57 µmol g-1) during 4-h of irradiation, which is 2.55 and 4.76 times compared to pristine BiOCl nanosheets, respectively. Isotope tracer experiments suggest that the obtained carbon-based products are generated through CO2 photoreduction in the presence of water molecule under irradiation. Moreover, in situ Fourier-transform infrared spectroscopy (in situ FTIR) results indicate the formation of *CHO, *CH3O, b-CO32-, m-CO32-, HCO-3, HCOOH, *COOH, and HCOO- species during the CO2 reduction process and a possible mechanism for CO2 photoreduction into CO and CH4 is proposed based on these findings. After 25-h of CO2 photoreduction reaction, the yields of CO and CH4 continue to increase. Furthermore, the stability of the prepared material is confirmed by XRD pattern, XPS analysis, and TEM image. These outcomes underscore an effective strategy for constructing advanced photocatalysts tailored for high-performance solar-driven CO2 reduction.
2024, 40(7): 230801
doi: 10.3866/PKU.WHXB202308017
Abstract:
Selective hydrogenation of CO2 to methanol with renewable H2 is a promising approach to effectively utilize the anthropogenic greenhouse gas CO2 in response to the growing environmental and energy challenges. Recently, MoS2 has gained attention as an attractive catalyst for CO2 hydrogenation due to its tunable S vacancy sites. However, its catalytic reactivity towards methanol production is still unsatisfactory because the general edge S vacancy site tends to favor CH4 formation. Herein, we report that the alkali K decorated MoS2 catalyst enables a dramatically enhancement in selective hydrogenation of CO2 to methanol, in contrast to the pristine MoS2 nanosheets that produce mainly CH4. We incorporated the K promoter into MoS2 using a simple physical mixture method, and we found that the loading of K has a crucial impact on the catalytic performance. The K-MoS2 catalyst with an appropriate K loading of 0.5 wt.% (mass fraction) delivers an optimized methanol selectivity of 81% and a methanol space time yield of 3.6 mmol·g-1·h-1 at mild reaction conditions of 220 °C and 5 MPa, which greatly outperforms the bare MoS2. Higher K loading would lead CO as the dominating product, while lower K loading is insufficient to tune the selectivity. Detailed characterization techniques, including X-ray diffraction (XRD), Raman, H2-temperature programmed reduction (TPR), electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS), CO-diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and H2-D2-temperature programmed surface reaction (TPSR), reveal that K atoms tend to occupy the edge sites on MoS2 and serve as electron donators, which enhance the density of states at the Fermi surface and the basicity of the edge active sites, while preventing H2 dissociation on the edge S vacancy. The reaction mechanism, as studied by CO2-temperature programmed desorption (TPD) and CO2 + H2 DRIFTS, suggests a reverse water-gas shift route for CO2hydrogenation to methanol. The increased basicity at the edge active site has therefore facilitates CO2 adsorption and lowers the activation barrier for CO2 dissociation to CO. It also restrains the methanation activity of intermediate CO and directs the reaction path toward CO hydrogenation to methanol. However, the excessive inhibition of H2 dissociation at higher K loading levels causes the facile desorption of CO, resulting in high CO selectivity. These results highlight the appearing effect of K promoter on modulating the edge active sites of MoS2 to favor methanol formation over CH4, and provide a simple yet effective strategy for tuning the structure and catalytic performance of MoS2. This extends the application of MoS2-based catalysts in methanol synthesis via CO2 hydrogenation.
Selective hydrogenation of CO2 to methanol with renewable H2 is a promising approach to effectively utilize the anthropogenic greenhouse gas CO2 in response to the growing environmental and energy challenges. Recently, MoS2 has gained attention as an attractive catalyst for CO2 hydrogenation due to its tunable S vacancy sites. However, its catalytic reactivity towards methanol production is still unsatisfactory because the general edge S vacancy site tends to favor CH4 formation. Herein, we report that the alkali K decorated MoS2 catalyst enables a dramatically enhancement in selective hydrogenation of CO2 to methanol, in contrast to the pristine MoS2 nanosheets that produce mainly CH4. We incorporated the K promoter into MoS2 using a simple physical mixture method, and we found that the loading of K has a crucial impact on the catalytic performance. The K-MoS2 catalyst with an appropriate K loading of 0.5 wt.% (mass fraction) delivers an optimized methanol selectivity of 81% and a methanol space time yield of 3.6 mmol·g-1·h-1 at mild reaction conditions of 220 °C and 5 MPa, which greatly outperforms the bare MoS2. Higher K loading would lead CO as the dominating product, while lower K loading is insufficient to tune the selectivity. Detailed characterization techniques, including X-ray diffraction (XRD), Raman, H2-temperature programmed reduction (TPR), electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS), CO-diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and H2-D2-temperature programmed surface reaction (TPSR), reveal that K atoms tend to occupy the edge sites on MoS2 and serve as electron donators, which enhance the density of states at the Fermi surface and the basicity of the edge active sites, while preventing H2 dissociation on the edge S vacancy. The reaction mechanism, as studied by CO2-temperature programmed desorption (TPD) and CO2 + H2 DRIFTS, suggests a reverse water-gas shift route for CO2hydrogenation to methanol. The increased basicity at the edge active site has therefore facilitates CO2 adsorption and lowers the activation barrier for CO2 dissociation to CO. It also restrains the methanation activity of intermediate CO and directs the reaction path toward CO hydrogenation to methanol. However, the excessive inhibition of H2 dissociation at higher K loading levels causes the facile desorption of CO, resulting in high CO selectivity. These results highlight the appearing effect of K promoter on modulating the edge active sites of MoS2 to favor methanol formation over CH4, and provide a simple yet effective strategy for tuning the structure and catalytic performance of MoS2. This extends the application of MoS2-based catalysts in methanol synthesis via CO2 hydrogenation.
2024, 40(7): 230605
doi: 10.3866/PKU.WHXB202306051
Abstract:
In recent years, there has been significant interest in the potential of probiotics to inhibit the growth of Helicobacter pylori (H. pylori), a bacterium known to cause gastric infections. However, the effectiveness of probiotics in combating H. pylori is often hindered by their susceptibility to gastric acid, making it challenging for them to survive and remain active in the stomach. To address this issue, researchers have turned to hydrogel encapsulation as a promising strategy to protect probiotics. Therefore, we designed a hydrogel-probiotic capsules possessed both acid resistance and magnetic drive properties to protect and targeted-deliver probiotics in gastric conditions. The probiotic capsules with core-shell structure prepared by the electrostatic spray method can encapsule the probiotic without damaging the activity of probiotic. The probiotic capsule was composed of a calcium alginate/CaCO3/FeCo@G (iron-cobalt magnetic graphitic nanocapsule) shell and a Laj (Lactobacillus Johnsonii, a kind of probiotics) core (Alg/CaCO3/FeCo@G-Laj, ACFL). The capsules were thoroughly characterized using field emission scanning electron microscopy and cell microscopic imaging to verify their morphology and their ability to encapsulate probiotics. The results indicated that ACFL capsules maintained their integrity during a 2-h incubation in DPBS (Dulbecco’s Phosphate-Buffered Saline) without releasing the probiotics, underscoring their robust encapsulation capacity. Moreover, ACFL could sustain the activity of Laj in SGF (simulated gastric fluid) for a long time by locally neutralizing the gastric acid through CaCO3. It’s worth noting that Laj exhibits considerable H. pylori inhibition properties by secreting lactic acid to damage H. pylori and by competing adsorption for gastric epithelial cells with H. pylori. ACFL capsules demonstrated significant H. pylori inhibition properties even after exposure to SGF, further supporting the protective effect of the encapsulation strategy on probiotic activity. Moreover, in order to achieve efficient bactericidal performance in the real system, it is necessary to design a power device to give the capsule active propulsion ability to realize targeted delivery of Laj. FeCo@G, which possesses brilliant stability in acid environment on account of the protective graphitic shell, was integrated in ACFL for efficient magnetically navigated delivery. The results show that ACFL can reach a velocity of 3 cm·s-1 under the guidance of an external magnetic field, which confirms the ability of ACFL capsule to be potent tool for target delivery of probiotics. In conclusion, ACFL capsules hold promise for effectively targeting the gastric wall and releasing active probiotics to combat H. pylori infections. The combination of acid-neutralizing properties and magnetic navigation not only maintains the viability of the probiotics but also minimizes disruption to gastric homeostasis. This innovative approach offers a new avenue for protecting and controlling the release of active agents in the challenging gastric environment, opening up possibilities for improved treatments and interventions.
In recent years, there has been significant interest in the potential of probiotics to inhibit the growth of Helicobacter pylori (H. pylori), a bacterium known to cause gastric infections. However, the effectiveness of probiotics in combating H. pylori is often hindered by their susceptibility to gastric acid, making it challenging for them to survive and remain active in the stomach. To address this issue, researchers have turned to hydrogel encapsulation as a promising strategy to protect probiotics. Therefore, we designed a hydrogel-probiotic capsules possessed both acid resistance and magnetic drive properties to protect and targeted-deliver probiotics in gastric conditions. The probiotic capsules with core-shell structure prepared by the electrostatic spray method can encapsule the probiotic without damaging the activity of probiotic. The probiotic capsule was composed of a calcium alginate/CaCO3/FeCo@G (iron-cobalt magnetic graphitic nanocapsule) shell and a Laj (Lactobacillus Johnsonii, a kind of probiotics) core (Alg/CaCO3/FeCo@G-Laj, ACFL). The capsules were thoroughly characterized using field emission scanning electron microscopy and cell microscopic imaging to verify their morphology and their ability to encapsulate probiotics. The results indicated that ACFL capsules maintained their integrity during a 2-h incubation in DPBS (Dulbecco’s Phosphate-Buffered Saline) without releasing the probiotics, underscoring their robust encapsulation capacity. Moreover, ACFL could sustain the activity of Laj in SGF (simulated gastric fluid) for a long time by locally neutralizing the gastric acid through CaCO3. It’s worth noting that Laj exhibits considerable H. pylori inhibition properties by secreting lactic acid to damage H. pylori and by competing adsorption for gastric epithelial cells with H. pylori. ACFL capsules demonstrated significant H. pylori inhibition properties even after exposure to SGF, further supporting the protective effect of the encapsulation strategy on probiotic activity. Moreover, in order to achieve efficient bactericidal performance in the real system, it is necessary to design a power device to give the capsule active propulsion ability to realize targeted delivery of Laj. FeCo@G, which possesses brilliant stability in acid environment on account of the protective graphitic shell, was integrated in ACFL for efficient magnetically navigated delivery. The results show that ACFL can reach a velocity of 3 cm·s-1 under the guidance of an external magnetic field, which confirms the ability of ACFL capsule to be potent tool for target delivery of probiotics. In conclusion, ACFL capsules hold promise for effectively targeting the gastric wall and releasing active probiotics to combat H. pylori infections. The combination of acid-neutralizing properties and magnetic navigation not only maintains the viability of the probiotics but also minimizes disruption to gastric homeostasis. This innovative approach offers a new avenue for protecting and controlling the release of active agents in the challenging gastric environment, opening up possibilities for improved treatments and interventions.
