Photocatalytic CO_(2)reduction to produce high value-added carbon-based fuel has been proposed as a promising approach to mitigate global warming issues.However,the conversion efficiency and product selectivity are st...Photocatalytic CO_(2)reduction to produce high value-added carbon-based fuel has been proposed as a promising approach to mitigate global warming issues.However,the conversion efficiency and product selectivity are still low due to the sluggish dynamics of transfer processes involved in proton-assisted multi-electron reactions.Lowering the formation energy barriers of intermediate products is an effective method to enhance the selectivity and productivity of final products.In this study,we aim to regulate the surface electronic structure of Bi_(2)WO_(6)by doping surface chlorine atoms to achieve effective photocatalytic CO_(2)reduction.Surface Cl atoms can enhance the absorption ability of light,affect its energy band structure and promote charge separation.Combined with DFT calculations,it is revealed that surface Cl atoms can not only change the surface charge distribution which affects the competitive adsorption of H_(2)O and CO_(2),but also lower the formation energy barrier of intermediate products to generate more intermediate*COOH,thus facilitating CO production.Overall,this study demonstrates a promising surface halogenation strategy to enhance the photocatalytic CO_(2)reduction activity of a layered structure Bi-based catalyst.展开更多
CONSPECTUS:Catalyzing the oxygen evolution reaction(OER)is important for key energy-storage technologies,particularly water electrolysis and photoelectrolysis for hydrogen fuel production.Under neutral-to-alkaline con...CONSPECTUS:Catalyzing the oxygen evolution reaction(OER)is important for key energy-storage technologies,particularly water electrolysis and photoelectrolysis for hydrogen fuel production.Under neutral-to-alkaline conditions,first-row transitionmetal oxides/(oxy)hydroxides are the fastest-known OER catalysts and have been the subject of intense study for the past decade.Critical to their high performance is the intentional or accidental addition of Fe to Ni/Co oxides that convert to layered(oxy)hydroxide structures during the OER.Unraveling the role that Fe plays in the catalysis and the molecular identity of the true“active site”has proved challenging,however,due to the dynamics of the host structure and absorbed Fe sites as well as the diversity of local structures in these disordered active phases.In this Account,we highlight our work to understand the role of Fe in Ni/Co(oxy)hydroxide OER catalysts.We first discuss how we characterize the intrinsic activity of the first-row transition-metal(oxy)hydroxide catalysts as thin films by accounting for the contributions of the catalyst-layer thickness(mass loading)and electrical conductivity as well as the underlying substrate’s chemical interactions with the catalyst and the presence of Fe species in the electrolyte.We show how Fe-doped Ni/Co(oxy)hydroxides restructure during catalysis,absorb/desorb Fe,and in some cases degrade or regenerate their activity during electrochemical testing.We highlight the relevant techniques and procedures that allowed us to better understand the role of Fe in activating other first-row transition metals for OER.We find several modes of Fe incorporation in Ni/Co(oxy)hydroxides and show how those modes correlate with activity and durability.We also discuss how this understanding informs the incorporation of earthabundant transition-metal OER catalysts in anion-exchange-membrane water electrolyzers(AEMWE)that provide a locally basic anode environment but run on pure water and have advantages over the more-developed proton-exchange-membrane water electrolyzers(PEMWE)that use platinum-group-metal(PGM)catalysts.We outline the key issues of introducing Fe-doped Ni/Co(oxy)hydroxide catalysts at the anode of the AEMWE,such as the oxidative processes triggered by Fe species traveling through the polymer membrane,pH-gradient effects on the catalyst stability,and possibly limited catalyst utilization in the compressed stack configuration.We also suggest possible mitigation strategies for these issues.Finally,we summarize remaining challenges including the long-term stability of Fe-doped Ni/Co(oxy)hydroxides under OER conditions and the lack of accurate models of the dynamic active surface that hinder our understanding of,and thus ability to design,these catalysts.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.51708078)Natural Science Foundation of Chongqing(Grant No.CSTB2022NSCQ-MSX0815)+2 种基金Science and Technology Research Program of Chongqing Municipal Education Commission(Grant No.KJQN202200542)the Chongqing Innovative Research Group Project(Grant No.CXQT21015)Foundation of Chongqing Normal University(22XLB022).
文摘Photocatalytic CO_(2)reduction to produce high value-added carbon-based fuel has been proposed as a promising approach to mitigate global warming issues.However,the conversion efficiency and product selectivity are still low due to the sluggish dynamics of transfer processes involved in proton-assisted multi-electron reactions.Lowering the formation energy barriers of intermediate products is an effective method to enhance the selectivity and productivity of final products.In this study,we aim to regulate the surface electronic structure of Bi_(2)WO_(6)by doping surface chlorine atoms to achieve effective photocatalytic CO_(2)reduction.Surface Cl atoms can enhance the absorption ability of light,affect its energy band structure and promote charge separation.Combined with DFT calculations,it is revealed that surface Cl atoms can not only change the surface charge distribution which affects the competitive adsorption of H_(2)O and CO_(2),but also lower the formation energy barrier of intermediate products to generate more intermediate*COOH,thus facilitating CO production.Overall,this study demonstrates a promising surface halogenation strategy to enhance the photocatalytic CO_(2)reduction activity of a layered structure Bi-based catalyst.
基金funded by National Science Foundation grant 1955106DOE EERE grant DE-EE0008841.
文摘CONSPECTUS:Catalyzing the oxygen evolution reaction(OER)is important for key energy-storage technologies,particularly water electrolysis and photoelectrolysis for hydrogen fuel production.Under neutral-to-alkaline conditions,first-row transitionmetal oxides/(oxy)hydroxides are the fastest-known OER catalysts and have been the subject of intense study for the past decade.Critical to their high performance is the intentional or accidental addition of Fe to Ni/Co oxides that convert to layered(oxy)hydroxide structures during the OER.Unraveling the role that Fe plays in the catalysis and the molecular identity of the true“active site”has proved challenging,however,due to the dynamics of the host structure and absorbed Fe sites as well as the diversity of local structures in these disordered active phases.In this Account,we highlight our work to understand the role of Fe in Ni/Co(oxy)hydroxide OER catalysts.We first discuss how we characterize the intrinsic activity of the first-row transition-metal(oxy)hydroxide catalysts as thin films by accounting for the contributions of the catalyst-layer thickness(mass loading)and electrical conductivity as well as the underlying substrate’s chemical interactions with the catalyst and the presence of Fe species in the electrolyte.We show how Fe-doped Ni/Co(oxy)hydroxides restructure during catalysis,absorb/desorb Fe,and in some cases degrade or regenerate their activity during electrochemical testing.We highlight the relevant techniques and procedures that allowed us to better understand the role of Fe in activating other first-row transition metals for OER.We find several modes of Fe incorporation in Ni/Co(oxy)hydroxides and show how those modes correlate with activity and durability.We also discuss how this understanding informs the incorporation of earthabundant transition-metal OER catalysts in anion-exchange-membrane water electrolyzers(AEMWE)that provide a locally basic anode environment but run on pure water and have advantages over the more-developed proton-exchange-membrane water electrolyzers(PEMWE)that use platinum-group-metal(PGM)catalysts.We outline the key issues of introducing Fe-doped Ni/Co(oxy)hydroxide catalysts at the anode of the AEMWE,such as the oxidative processes triggered by Fe species traveling through the polymer membrane,pH-gradient effects on the catalyst stability,and possibly limited catalyst utilization in the compressed stack configuration.We also suggest possible mitigation strategies for these issues.Finally,we summarize remaining challenges including the long-term stability of Fe-doped Ni/Co(oxy)hydroxides under OER conditions and the lack of accurate models of the dynamic active surface that hinder our understanding of,and thus ability to design,these catalysts.
