| The energy crisis and environmental pollution,accompanying with the rapid development of industry,have received more and more attention and become an important issue that need to be resolved urgently.In 1972,Fujishima and Honda used the rutile titanium dioxide single crystal photoelectrode for photoelectrocatalyrtic water splitting for hydrogen evolution.Subsequently,scientists achieved photocatalytic hydrogen production from water splitting using power semiconductor materials.Since then,the research on the use of inexhaustible solar energy to produce green hydrogen energy has attracted more and more concern.Whatever for photoelectrocatalysis or photocatalysis,the key issue of study is semiconductor catalyst material.Recently,semiconductors with d10 electron configuration have attracted wide attention owing to their excellent carrier transfer efficiency and good photocatalytic performance.In this thesis,ZnGa2O4 with d10 electronic configuration act as the main photocatalyst materials for study.Non-metal elements doping and heterostructure construction with modification of defects were used to improve the photocatalytic activity of ZnGa204 photocatalyst.The main research content and related conclusions are as follows:In the second chapter,we present a facile method to prepare B/N-codoped ZnGa2O4 nanospheres accompanied with oxygen vacancy modification by using ammonia as nitrogen source and NaBH4 as boron source and reducing agent.The Vo-modified B/N-codoped ZnGa2O4(Vo-B/N-ZGO)exhibits excellent photocatalytic hydrogen production efficiency even without any additional cocatalyst,which is better than the Vo-modified B-doped ZnGa2O4(Vo-B-ZGO)or N-doped ZnGa2O4(N-ZGO)samples and as high as about three times that of undoped ZnGa2O4.This superior photocatalytic performance of Vo-B/N-ZGO could be explained based on the following reasons.For one,the synergetic effect of boron and nitrogen dopants with oxygen vacancies greatly broadens its light absorption range.For another,the Vo-modified B/N-codoping obviously enhances carrier separation and also produces rich reactive sites for proton reduction reaction.In addition,the theoretical calculation was combined with experimental characterization to explain the mechanism of ZnGa2O4 photocatalytic reaction.In the third chapter,we successfully prepared ZnS/ZnGa2O4 heterostructure through in-situ growth of ZnS in 100℃ aqueous solution with Na2S as S source and ZnGa2O4 as Zn source as well as photocatalyst substrate.The content of ZnS phase is controlled by changing the concentration of Na2S solution.It was found that the photocatalytic hydrogen production of photocatalyst first increased and then decreased with the increase of ZnS.When the concentration of Na2S solution was 0.02 M,the composite material manifest the best photocatalytic hydrogen evolution rate,up to 1064 umol/g/h,which is more than 8 times of ZnGa2O4.The heterojunction at the interface of ZnS/ZnGa2O4 photocatalyst promotes the separation of carriers and the dramatically enhanced photocatalytic activity.However,since the Zn atoms of ZnS are derived from ZnGa2O4 substrate,more Zn atoms will be lost and becoming recombinatio center with the increase of ZnS content,which is not conducive to photocatalytic activity.Therefore,the photocatalytic hydrogen production performance of composite heterojunction materials shows a trend of increasing first and then decreasing as the proportion of zinc sulfide increases.In the fourth chapter,the research work and related innovation point have been summarized and further research work has also been put forward. |
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