| Energy shortage and environmental deterioration have become two major problems affecting human survival.Solar energy and hydrogen energy are sustainable and clean energy sources.Therefore,photocatalytic water decomposition to produce hydrogen by converting solar energy into hydrogen energy shows great strategic significance,which can greatly decrease the use of fossil fuels and control the emissions of greenhouse gas.As an organic conjugated polymer,polyimide（PI）has received more and more attentions,because of its wide range of sources,simple preparation method,low cost,and adjustable properties.However,due to the special carrier transport mode of polyimide semiconductors,its photoelectric conversion efficiency is limited and its absorption for visible light is insufficient,which limit its performance of photocatalytic decomposition of water to produce hydrogen.As p-type semiconductors,CuO and CuS have attracted wide attention in the field of photocatalysis due to their excellent photoelectric properties,economical raw materials and easy preparation.However,since their inappropriate energy band positions and fast carrier recombination,it is necessary to build a composite system with other semiconductors to improve the photocatalytic activity.In this study,CuO and CuS nanocrystals were grown on the surface of polyimide photocatalytic materials to construct a composite photocatalytic material system.The interface carrier transport mechanism was investigated in depth.Under visible light irradiation,the hydrogen production of composite photocatalytic material system was tested.The major research contents were showed as follows:1.Research of direct Z-scheme CuO/PI composite material and its photocatalytic activityBy growing CuO nanocrystals on PI surface through heat treatment in a solvent,a direct Z-scheme CuO/PI heterojunction photocatalytic material system was prepared.Compared with pure PI,CuO/PI heterojunction exhibits stronger light absorption ability in the visible light region,and inhibits the recombination of photogenerated carriers through the direct Z-scheme charge transfer path.Under visible light irradiation,20%CuO/PI reaches the highest hydrogen production within 4 hours,about 418.4μmol·g-1,which is approximately 32 times as high as that of pure PI.At the same time,the CuO/PI heterojunction also shows excellent stability.It was found that the conduction band position of the p-type CuO semiconductor with weak photocatalytic reduction ability was effectively improved.Based on the Z-scheme charge transport path of heterojunction system,the performance of photocatalytic water splitting to hydrogen is further improved.2.Research of the photocatalytic activity of CuS/PI system based on photoinduced interfacial charge transferA novel CuS/PI composite photocatalyst was prepared by in situ crystallization of CuS nanocrystals on the surface of PI.CuS/PI composite exhibits good photocatalytic hydrogen production and excellent photocatalytic stability.At 5%loading amount of CuS on PI,the activity reaches the highest,which is 71.2 times and 33.4 times as high as that of pristine PI and CuS,correspondingly.The photoelectric properties of CuS/PI were studied by a series of characterization tests,which showed that the combination of CuS and PI accelerated the transmission of carriers and inhibited the recombination of photogenerated electrons and holes.In addition,photogenerated electrons transfer from the valence band of PI to CuS through photoinduced interfacial charge transfer（IFCT）.This interfacial charge transfer mechanism greatly inhibits the electron-hole recombination of PI and the system can accept more photogenerated electrons from EY-,which significantly improves the photocatalytic hydrogen production of PI. |
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