Hydrogen(H_(2))is a clean,efficient,and renewable energy with zero carbon emission,which is expected to replace the extensively used fossil fuels.Photocatalytic water splitting is a promising strategy for sustainable ...Hydrogen(H_(2))is a clean,efficient,and renewable energy with zero carbon emission,which is expected to replace the extensively used fossil fuels.Photocatalytic water splitting is a promising strategy for sustainable H2 production.Nevertheless,the performance of single‐component photocatalysts is often confined by fast electron‐hole recombination due to strong Coulombic force,and their inability to simultaneously attain a wide absorption range and enough redox capabilities.These problems can be addressed by constructing a heterojunction between two semiconductors with different Fermi levels(EF),conduction band(CB)and valence band(VB)positions.Heterojunction promotes light harvesting through light absorption on both semiconductors and facilitates charge separation by decoupling them on different bands.There are mainly three types of heterojunctions,namely the type‐II heterojunction,the Z‐scheme heterojunction,and the step‐scheme(S‐scheme)heterojunction[1–3].In a type‐II heterojunction,photogenerated electrons migrate from the higher CB to the lower one,while photogenerated holes transfer from the lower to the higher VB.However,this schematic is thermodynamically flawed since the charge transfer discounts the redox powers of the electrons and holes.This transfer is also dynamically unfavorable due to strong repulsion between the photogenerated electrons(or holes)in different semiconductors.The Z‐scheme heterojunction utilizes dissolved redox ion pairs(traditional Z‐scheme)or conductive materials(all‐solid‐state Z‐scheme)as the shuttle for charge transfer and separation.However,the photogenerated carriers with stronger redox powers would preferentially react with the ion pairs or combine at the conductor because of stronger driving forces,leading to deducted redox powers and reduced photocatalytic activity.S‐scheme heterojunction could avoid these drawbacks and has exhibited excellent performance in organics degradation[4,5],CO_(2) reduction[6,7],hydrogen evolution[8],etc.展开更多
The mechanism of the proton_transfer_coupled electron transfer (PT_ET) reactions between the menaquinone Q A (MQ 1) and ubiquinone Q B (UQ 1) in the bacterial photosynthetic reaction center of Rhodopseudomona vi...The mechanism of the proton_transfer_coupled electron transfer (PT_ET) reactions between the menaquinone Q A (MQ 1) and ubiquinone Q B (UQ 1) in the bacterial photosynthetic reaction center of Rhodopseudomona viridis was studied by using the B3LYP/6_31G(d) method. The changes of standard Gibbs free energy ΔG 0 of all possible reactions followed the ET reaction (1) were calculated. The results indicated that: (1) according to the ΔG 0 values of corresponding reactions, UQ 1 could not accept two electrons from MQ - 1 continually without the coupled proton transfer reactions. Because of ΔG 0 2b 0, ΔG 0 3b 0 and ΔG 0 4b 0, the corresponding PT_ET reactions could take place along with reactions (2b), (3b) and (4b) sequentially; (2) on the gaseous condition, the first and second transferred protons (H +(1) and H +(2)) from the surrounding amino acid residues or water molecules will combine with the oxygen No.7 and oxygen No.8 of UQ 1, respectively. On the condition of protein surroundings (by SCRF model, ε =4.0), the results are converse but the energy difference between the combination of H +(1) and H +(2) with UQ - 1 is quite small. The difference of ΔG 0 values between the corresponding reactions in gaseous surroundings and the SCRF model is not significant; (3) the PT_ET reactions between MQ 1 - and UQ 1 - should be as follows: MQ 1 -+UQ 1→MQ 1+UQ 1 - (1) UQ 1 - ( O (7) )+H +( HisL 190)→UQ 1H(2b) ( Gas ) or UQ 1 - ( O (8) )+H +(H 2O)→UQ 1H (2b') ( SCRF ) or UQ 1 - ( O (8) )+H + ( ArgL 217)→UQ 1H(2b') ( SCRF ) MQ 1 -+UQ 1H→MQ 1+UQ 1H - (3b) ( Gas ) MQ 1 -+UQ 1H→MQ 1+UQ 1H -(3b') ( SCR F) UQ 1H -+H +(H 2O)→UQ 1H 2(4b) ( Gas ) or UQ 1H -+H + ( ArgL 217)→UQ 1H 2 (4b) ( Gas ) or UQ 1H -+H + ( HisL 190)→UQ 1H 2 (4b') ( SCRF )展开更多
Electrochemical CO_(2)reduction to value-added fuels and chemicals is recognized as a promising strategy to alleviate energy shortages and global warming owing to its high efficiency and economic feasibility.Recently,...Electrochemical CO_(2)reduction to value-added fuels and chemicals is recognized as a promising strategy to alleviate energy shortages and global warming owing to its high efficiency and economic feasibility.Recently,understanding the activity origin,selectivity regulation,and reaction mechanisms of CO_(2)reduction reactions(CO_(2)RRs)has become the focus of efficient electrocatalyst design.Polyoxometalates(POMs),a unique class of nanosized metal-oxo clusters,are promising candidates for the development of efficient CO_(2)RR electrocatalysts and,owing to their well-defined structure,remarkable electron/proton storage and transfer ability,and capacities for adsorption and activation of CO_(2),are ideal models for investigating the activity origin and reaction mechanisms of CO_(2)RR electrocatalysts.In this review,we focus on the activity origin and mechanism of CO_(2)RRs and survey recent advances that were achieved by employing POMs in electrocatalytic CO_(2)RRs.We highlight the significant roles of POMs in the electrocatalytic CO_(2)RR process and the main factors influencing selectivity regulation and catalytic CO_(2)RR performance,including the electrolyte,electron-transfer process,and surface characteristics.Finally,we offer a perspective of the advantages and future challenges of POM-based materials in electrocatalytic CO_(2)reduction that could inform new advancements in this promising research field.展开更多
The development of non‐precious metal catalysts that facilitate the oxygen evolution reaction(OER)is important for the widespread application of hydrogen production by water splitting.Various perovskite oxides have b...The development of non‐precious metal catalysts that facilitate the oxygen evolution reaction(OER)is important for the widespread application of hydrogen production by water splitting.Various perovskite oxides have been employed as active OER catalysts,however,the underlying mechanism that occurs at the catalyst‐electrolyte interface is still not well understood,prohibiting the design and preparation of advanced OER catalysts.Here,we report a systematic investigation into the effect of proton dynamics on the catalyst‐electrolyte interfaces of four perovskite catalysts:La_(0.5)Sr_(0.5)CoO_(3‐δ)(LSCO),LaCoO_(3),LaFeO_(3),and LaNiO_(3).The pH‐dependent OER activities,H/D kinetic isotope effect,and surface functionalization with phosphate anion groups were investigated to elucidate the role of proton dynamics in the rate‐limiting steps of the OER.For oxides with small charge‐transfer energies,such as LSCO and LaNiO_(3),non‐concerted proton‐coupled electron transfer steps are involved in the OER,and the activity is strongly controlled by the proton dynamics on the catalyst surface.The results demonstrate the important role of interfacial proton transfer in the OER mechanism,and suggest that proton dynamics at the interface should carefully be considered in the design of future high‐performance catalysts.展开更多
基金supported by the Institutional Fund Projects under grant no(IFPRC‐133‐130‐2020).Therefore,authors gratefully acknowledge technical and financial support from Ministry of Education and King Abdulaziz University,Jeddah,Saudi Arabia.
文摘Hydrogen(H_(2))is a clean,efficient,and renewable energy with zero carbon emission,which is expected to replace the extensively used fossil fuels.Photocatalytic water splitting is a promising strategy for sustainable H2 production.Nevertheless,the performance of single‐component photocatalysts is often confined by fast electron‐hole recombination due to strong Coulombic force,and their inability to simultaneously attain a wide absorption range and enough redox capabilities.These problems can be addressed by constructing a heterojunction between two semiconductors with different Fermi levels(EF),conduction band(CB)and valence band(VB)positions.Heterojunction promotes light harvesting through light absorption on both semiconductors and facilitates charge separation by decoupling them on different bands.There are mainly three types of heterojunctions,namely the type‐II heterojunction,the Z‐scheme heterojunction,and the step‐scheme(S‐scheme)heterojunction[1–3].In a type‐II heterojunction,photogenerated electrons migrate from the higher CB to the lower one,while photogenerated holes transfer from the lower to the higher VB.However,this schematic is thermodynamically flawed since the charge transfer discounts the redox powers of the electrons and holes.This transfer is also dynamically unfavorable due to strong repulsion between the photogenerated electrons(or holes)in different semiconductors.The Z‐scheme heterojunction utilizes dissolved redox ion pairs(traditional Z‐scheme)or conductive materials(all‐solid‐state Z‐scheme)as the shuttle for charge transfer and separation.However,the photogenerated carriers with stronger redox powers would preferentially react with the ion pairs or combine at the conductor because of stronger driving forces,leading to deducted redox powers and reduced photocatalytic activity.S‐scheme heterojunction could avoid these drawbacks and has exhibited excellent performance in organics degradation[4,5],CO_(2) reduction[6,7],hydrogen evolution[8],etc.
文摘The mechanism of the proton_transfer_coupled electron transfer (PT_ET) reactions between the menaquinone Q A (MQ 1) and ubiquinone Q B (UQ 1) in the bacterial photosynthetic reaction center of Rhodopseudomona viridis was studied by using the B3LYP/6_31G(d) method. The changes of standard Gibbs free energy ΔG 0 of all possible reactions followed the ET reaction (1) were calculated. The results indicated that: (1) according to the ΔG 0 values of corresponding reactions, UQ 1 could not accept two electrons from MQ - 1 continually without the coupled proton transfer reactions. Because of ΔG 0 2b 0, ΔG 0 3b 0 and ΔG 0 4b 0, the corresponding PT_ET reactions could take place along with reactions (2b), (3b) and (4b) sequentially; (2) on the gaseous condition, the first and second transferred protons (H +(1) and H +(2)) from the surrounding amino acid residues or water molecules will combine with the oxygen No.7 and oxygen No.8 of UQ 1, respectively. On the condition of protein surroundings (by SCRF model, ε =4.0), the results are converse but the energy difference between the combination of H +(1) and H +(2) with UQ - 1 is quite small. The difference of ΔG 0 values between the corresponding reactions in gaseous surroundings and the SCRF model is not significant; (3) the PT_ET reactions between MQ 1 - and UQ 1 - should be as follows: MQ 1 -+UQ 1→MQ 1+UQ 1 - (1) UQ 1 - ( O (7) )+H +( HisL 190)→UQ 1H(2b) ( Gas ) or UQ 1 - ( O (8) )+H +(H 2O)→UQ 1H (2b') ( SCRF ) or UQ 1 - ( O (8) )+H + ( ArgL 217)→UQ 1H(2b') ( SCRF ) MQ 1 -+UQ 1H→MQ 1+UQ 1H - (3b) ( Gas ) MQ 1 -+UQ 1H→MQ 1+UQ 1H -(3b') ( SCR F) UQ 1H -+H +(H 2O)→UQ 1H 2(4b) ( Gas ) or UQ 1H -+H + ( ArgL 217)→UQ 1H 2 (4b) ( Gas ) or UQ 1H -+H + ( HisL 190)→UQ 1H 2 (4b') ( SCRF )
文摘Electrochemical CO_(2)reduction to value-added fuels and chemicals is recognized as a promising strategy to alleviate energy shortages and global warming owing to its high efficiency and economic feasibility.Recently,understanding the activity origin,selectivity regulation,and reaction mechanisms of CO_(2)reduction reactions(CO_(2)RRs)has become the focus of efficient electrocatalyst design.Polyoxometalates(POMs),a unique class of nanosized metal-oxo clusters,are promising candidates for the development of efficient CO_(2)RR electrocatalysts and,owing to their well-defined structure,remarkable electron/proton storage and transfer ability,and capacities for adsorption and activation of CO_(2),are ideal models for investigating the activity origin and reaction mechanisms of CO_(2)RR electrocatalysts.In this review,we focus on the activity origin and mechanism of CO_(2)RRs and survey recent advances that were achieved by employing POMs in electrocatalytic CO_(2)RRs.We highlight the significant roles of POMs in the electrocatalytic CO_(2)RR process and the main factors influencing selectivity regulation and catalytic CO_(2)RR performance,including the electrolyte,electron-transfer process,and surface characteristics.Finally,we offer a perspective of the advantages and future challenges of POM-based materials in electrocatalytic CO_(2)reduction that could inform new advancements in this promising research field.
文摘The development of non‐precious metal catalysts that facilitate the oxygen evolution reaction(OER)is important for the widespread application of hydrogen production by water splitting.Various perovskite oxides have been employed as active OER catalysts,however,the underlying mechanism that occurs at the catalyst‐electrolyte interface is still not well understood,prohibiting the design and preparation of advanced OER catalysts.Here,we report a systematic investigation into the effect of proton dynamics on the catalyst‐electrolyte interfaces of four perovskite catalysts:La_(0.5)Sr_(0.5)CoO_(3‐δ)(LSCO),LaCoO_(3),LaFeO_(3),and LaNiO_(3).The pH‐dependent OER activities,H/D kinetic isotope effect,and surface functionalization with phosphate anion groups were investigated to elucidate the role of proton dynamics in the rate‐limiting steps of the OER.For oxides with small charge‐transfer energies,such as LSCO and LaNiO_(3),non‐concerted proton‐coupled electron transfer steps are involved in the OER,and the activity is strongly controlled by the proton dynamics on the catalyst surface.The results demonstrate the important role of interfacial proton transfer in the OER mechanism,and suggest that proton dynamics at the interface should carefully be considered in the design of future high‐performance catalysts.
