Polymeric perylene diimide(PDI)has been evidenced as a good candidate for photocatalytic water oxidation,yet the origin of the photocatalytic oxygen evolution activity remains unclear and needs further exploration.Her...Polymeric perylene diimide(PDI)has been evidenced as a good candidate for photocatalytic water oxidation,yet the origin of the photocatalytic oxygen evolution activity remains unclear and needs further exploration.Herein,with crystal and atomic structures of the self-assembled PDI revealed from the X-ray diffraction pattern,the electronic structure is theoretically illustrated by the first-principles density functional theory calculations,suggesting the suitable band structure and the direct electronic transition for efficient photocatalytic oxygen evolution over PDI.It is confirmed that the carbonyl O atoms on the conjugation structure serve as the active sites for oxygen evolution reaction by the crystal orbital Hamiltonian group analysis.The calculations of reaction free energy changes indicate that the oxygen evolution reaction should follow the reaction pathway of H_(2)O→^(*)OH→^(*)O→^(*)OOH→^(*)O_(2)with an overpotential of 0.81 V.Through an in-depth theoretical computational analysis in the atomic and electronic structures,the origin of photocatalytic oxygen evolution activity for PDI is well illustrated,which would help the rational design and modification of polymeric photocatalysts for efficient oxygen evolution.展开更多
Owing to the growing consumption of non-renewable resources and increased environmental pollution,significant attention has been directed toward developing renewable and environmentally friendly energy sources.Hydroge...Owing to the growing consumption of non-renewable resources and increased environmental pollution,significant attention has been directed toward developing renewable and environmentally friendly energy sources.Hydrogen has emerged as a clean energy carrier and is considered an ideal chemical for power generation via fuel cells.Using renewable energy to power hydrogen production is an attractive prospect,and hydrogen production through photoelectrochemical water splitting is considered a promising area of interest;consequently,significant research is being conducted on rationally designed photoelectrodes.Generally,a photocathode for hydrogen evolution must have a conduction band that is more negative than the reduction potential of hydrogen.Numerous photocathode materials have been developed based on this premise;these include p-Si,InP,and GaN.Compared with other photocathode materials,Cu-based compounds are advantageous owing to their low preparation costs and diverse chemical states.For example,Cu_(2)O is a non-toxic p-type metal oxide semiconductor material with an appropriate band structure for water splitting and a direct band gap of 1.9-2.2 eV.Furthermore,the production of Cu_(2)O is facile,and the required materials are abundant;thus,it has attracted significant interest as a material for photocathodes.However,Cu_(2)O suffers from rapid recombination of photogenerated carriers and severe photo-corrosion,leading to unsatisfactory efficiency and poor stability.Intrinsically,the poor photo-stability of Cu_(2)O can be attributed to the location of the redox potential of Cu_(2)O within its bandgap,owing to which photoelectrons tend to preferentially reduce Cu_(2)O to Cu rather than reduce water to reduction.Therefore,Cu_(2)O itself is not an ideal hydrogen evolution catalyst.Thus,co-catalysts are necessary to improve its hydrogen evolution activity and photostability.In addition to co-catalysts,combining Cu_(2)O with tailored n-type semiconductors to generate built-in electric fields of p-n junctions has attracted extensive attention owing to its ability of increasing the separation of photogenerated carriers.Similarly,applying a hole transfer layer on the substrate can promote photocarrier separation.Furthermore,considering that water is indispensable for Cu_(2)O reduction,one effective approach to improve the stability of Cu_(2)O is the addition of a protective/passivation layer to isolate Cu_(2)O from water in aqueous electrolytes.In this review,we provide a brief overview of the mechanism of photoelectrochemical water splitting and the band structure of Cu_(2)O ;preparation methods of Cu_(2)O photocathodes;strategies to improve the efficiency and stability of Cu_(2)O photocathodes,including the construction of p-n junctions,integration with co-catalysts,and modifications using hole transport layers;advanced photoelectrochemical characterization techniques;and a discussion regarding the direction of future photocathode research.展开更多
基金supported by National Natural Science Foundation of China(No.523B2070,No.52225606).
文摘Polymeric perylene diimide(PDI)has been evidenced as a good candidate for photocatalytic water oxidation,yet the origin of the photocatalytic oxygen evolution activity remains unclear and needs further exploration.Herein,with crystal and atomic structures of the self-assembled PDI revealed from the X-ray diffraction pattern,the electronic structure is theoretically illustrated by the first-principles density functional theory calculations,suggesting the suitable band structure and the direct electronic transition for efficient photocatalytic oxygen evolution over PDI.It is confirmed that the carbonyl O atoms on the conjugation structure serve as the active sites for oxygen evolution reaction by the crystal orbital Hamiltonian group analysis.The calculations of reaction free energy changes indicate that the oxygen evolution reaction should follow the reaction pathway of H_(2)O→^(*)OH→^(*)O→^(*)OOH→^(*)O_(2)with an overpotential of 0.81 V.Through an in-depth theoretical computational analysis in the atomic and electronic structures,the origin of photocatalytic oxygen evolution activity for PDI is well illustrated,which would help the rational design and modification of polymeric photocatalysts for efficient oxygen evolution.
文摘Owing to the growing consumption of non-renewable resources and increased environmental pollution,significant attention has been directed toward developing renewable and environmentally friendly energy sources.Hydrogen has emerged as a clean energy carrier and is considered an ideal chemical for power generation via fuel cells.Using renewable energy to power hydrogen production is an attractive prospect,and hydrogen production through photoelectrochemical water splitting is considered a promising area of interest;consequently,significant research is being conducted on rationally designed photoelectrodes.Generally,a photocathode for hydrogen evolution must have a conduction band that is more negative than the reduction potential of hydrogen.Numerous photocathode materials have been developed based on this premise;these include p-Si,InP,and GaN.Compared with other photocathode materials,Cu-based compounds are advantageous owing to their low preparation costs and diverse chemical states.For example,Cu_(2)O is a non-toxic p-type metal oxide semiconductor material with an appropriate band structure for water splitting and a direct band gap of 1.9-2.2 eV.Furthermore,the production of Cu_(2)O is facile,and the required materials are abundant;thus,it has attracted significant interest as a material for photocathodes.However,Cu_(2)O suffers from rapid recombination of photogenerated carriers and severe photo-corrosion,leading to unsatisfactory efficiency and poor stability.Intrinsically,the poor photo-stability of Cu_(2)O can be attributed to the location of the redox potential of Cu_(2)O within its bandgap,owing to which photoelectrons tend to preferentially reduce Cu_(2)O to Cu rather than reduce water to reduction.Therefore,Cu_(2)O itself is not an ideal hydrogen evolution catalyst.Thus,co-catalysts are necessary to improve its hydrogen evolution activity and photostability.In addition to co-catalysts,combining Cu_(2)O with tailored n-type semiconductors to generate built-in electric fields of p-n junctions has attracted extensive attention owing to its ability of increasing the separation of photogenerated carriers.Similarly,applying a hole transfer layer on the substrate can promote photocarrier separation.Furthermore,considering that water is indispensable for Cu_(2)O reduction,one effective approach to improve the stability of Cu_(2)O is the addition of a protective/passivation layer to isolate Cu_(2)O from water in aqueous electrolytes.In this review,we provide a brief overview of the mechanism of photoelectrochemical water splitting and the band structure of Cu_(2)O ;preparation methods of Cu_(2)O photocathodes;strategies to improve the efficiency and stability of Cu_(2)O photocathodes,including the construction of p-n junctions,integration with co-catalysts,and modifications using hole transport layers;advanced photoelectrochemical characterization techniques;and a discussion regarding the direction of future photocathode research.
