Surface Regulation For Improvement Of Photogenerated Charge Separation Efficiency Of Ta₃N₅ And BiVO₄

Since the Industrial Revolution,with the continuous exploitation of fossil fuels,the problems of energy shortage and environmental pollution have become increasingly serious.The use of semiconductor photocatalytic technology to split water for hydrogen and convert CO2 to hydrocarbon fuels with low-pollution is one of the most promising ways to solve the energy crisis and environmental problems simultaneously.Tantalum nitride and bismuth vanadate with high theoretical solar energy conversion efficiency have been widely used in photocatalytic water splitting and photocatalytic reduction of CO2 system.However,the severe recombination of photogenerated carriers always restricts their actual photocatalytic reaction efficiency In this dissertation,in order to avoid the traditional amorphous heterojunction catalytic system which may bring the carrier recombination sites,"surface electric field" and "fast electron transport channel" are constructed in the tantalum nitride and bismuth vanadate-based semiconductors respectively through the nanocrystal interface-controlled strategy.The synthesized samples effectively enhances the spatial separation ability of their photogenerated carriers,and achieves higher photocatalytic activities of water splitting and CO2 reduction,which can provide the new design ideas for other photocatalytic materials.In this paper,the Ta3N5 cuboid with co-exposed {010} and {001} crystal facets and facet-dependent BiVO4{010}-Au-Cu2O heterostructure have been synthesized.The main contents are as follows:(1)The[100]crystal-oriented Ta3N5 cuboids with dominant coexposed {010}and {001} lateral plane was prepared by nitriding reaction with assistance of molten salts and exhibited a significant improvement in photoreduction of CO2 and a 0.42 VRHE(reference to reversible hydrogen electrode)photocurrent onset potential for photoelectrochemical water splitting.Exposing {001} facets with high work function on Ta3N5 cuboid to induce a significant surface band bending,and transferring charges along brachydiagonal direction were effectively to facilitate the spatial separation of photoinduced charges.The separation of the oxidation site from the reduction site greatly increases the activity of the photocatalytic reaction.This work may provide a new strategy for developing more efficient transition metal nitride photocatalysts with visible light absorption based on semiconductor nanocrystal engineering.(2)A fantastic crystal facet-dependent hetero structure with BiVO4{010}-Au-Cu2O have been successfully constructed through directionally anchoring of Au-Cu2O cell-shell layer onto the {010} facet of BiVO4 truncated octahedron for the first time and exhibited a significant improvement in photoreduction of CO2 with the long-lived activity.By means of single-particle PL analysis and theoretical simulation,it was suggested that the formation of Schottky junction in BiVO4{010}-Au interface facilitates extracting of photogenerated electrons from BiVO4 to Cu2O,which was certainly beneficial for prolonging the surviving times of both electrons in conduction band of Cu2O and holes in valence band of BiVO4.This work combines the advantages of surface-induced charge directional distribution and optimal metal-semiconductor contacted interface to provide a fast electron transfer channel with activated photocatalytic activity may provide a new strategy for developing more efficient composite photocatalysts.