Preparation And Properties Of Visible Light Responsive Photocatalysts For Total Water Splitting

The rapid development of human society inevitably brings negative effects such as energy shortage and environmental pollution.In order to achieve sustainable development,scientists are striving to find clean and efficient new energy sources that can replace traditional fossil energy.Solar energy is an inexhaustible energy source,and hydrogen energy has also received extensive attention due to its high calorific value and clean combustion products.In recent years,the use of photocatalytic water splitting technology to convert solar energy into hydrogen energy that can be stored and utilized has received extensive attention from researchers.However,most of the current catalysts either have poor response to visible light or serious photogenerated carrier recombination,which severely limits their applications.CdS and ZnS are common semiconductor photocatalysts,but ZnS with a single metal component has the disadvantages of wide band gap and no response to visible light,while Cd S has poor photocorrosion resistance and certain toxicity.The use of Znto partially replace Cd forms ZnCd S binary metal solid solution sulfides can overcome the shortcomings of single metal components to a certain extent.In addition,by adjusting the Zn/Cd ratio in the preparation process,the energy band structure of the catalyst can be adjusted,and a catalytic material that is more photocorrosion resistant in response to visible light can be prepared,but ZnCd S still has the problem of photogenerated carrier recombination.In the first part of this work,the authors prepared highly efficient photocatalysts for total water splitting by controlling the morphology and innovatively supporting cocatalysts.g-C₃N₄has been widely used in the research of photo-splitting water for hydrogen production due to its low cost precursor material and semiconductor band gap suitable for the visible light region,and Bi VO₄is often used for photocatalytic oxygen production.g-C₃N₄and Bi VO₄were respectively loaded with cocatalysts and then combined by electrostatic self-assembly to prepare a total water splitting photocatalyst.The first part:Two kinds of ZnCdS with different morphologies were prepared by solvothermal method,ordinary granular ZnCd S（o-ZCS）and flower-shaped ZnCd S（f-ZCS）.Two methods of traditional photodeposition and electrostatic self-assembly were used to load cocatalysts on the surface of f-ZCS.The electrostatic self-assembly method is to treat ZnCd S with（3-aminopropyl）triethoxysilane（APTES）to make it positively charged,and then combine it with negatively charged Pt colloids to synthesize a-Pt/f-ZCS photocatalysts through electrostatic attraction.The results of comparative experiments show that the activity of the photocatalyst a-Pt/f-ZCS obtained by electrostatic self-assembly is significantly higher than that of the d-Pt/f-ZCS catalyst obtained by traditional photodeposition.Then,in this work,a-Pt/o-ZCS photocatalyst was prepared by electrostatic self-assembly method,and the test results showed that its activity was much lower than that of a-Pt/f-ZCS.The characterization results of optical and optoelectronic properties show that compared with o-ZCS,f-ZCS has higher photo-generated carrier separation efficiency,and its visible light utilization is further greatly improved after effectively loading Pt.The second part:g-C₃N₄was prepared by high temperature solid-phase method,and then ultrasonically processed into nanosheet CNN,and then loaded with Pt additives to enhance the visible light absorption of Pt-CNN;Ag-Bi VO₄photocatalyst was prepared on the surface of Bi VO₄by loading Ag to improve its photocatalysis oxygen production performance.Finally,Pt-CNN was treated with APTES to make it positively charged,and electrostatically self-assembled with negatively charged Ag-Bi VO₄to form a Pt-CNN/Ag-Bi VO₄photocatalyst.The photocatalytic total water splitting performance of the catalyst was optimized by adjusting the amount of supported Ag,and its catalytic activity was the highest when the Ag content was10 wt%of Bi VO₄.Experiments show that Ag loaded with appropriate content can more efficiently inhibit the recombination of photogenerated carriers,thereby improving the catalytic performance.