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
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.
