| At present,when fossil energy is widely used,environmental pollution,climate change and the possible depletion of fossil energy in the future are inevitable problems.Compared with the fossil energy hydrogen as a fuel combustion product only water,so the wide application of hydrogen is expected to replace traditional fossil energy and improve the environmental pollution and climate change caused by the heavy use of traditional fossil energy.Hydrogen can be produced by splitting water,which means that hydrogen is both environmentally friendly and recyclable.The main way to decompose water to produce hydrogen is electrocatalysis and photocatalysis,but the electric energy in electrocatalysis needs to be converted by other energy sources,and the main source of electric energy conversion is the heat energy of burning fossil fuels.Compared with the solar energy required for electric energy photocatalysis,it can be directly obtained and has a wide range of sources,with fewer times of energy conversion and less energy loss.Cd S photocatalysts have been widely studied because of their narrow band gap,but the photocorrosion effect of Cd S seriously affects the stability of the photocatalytic reaction,and the photogenerated electrons in Cd S are easy to recombine with holes,both of which have a serious impact on the photocatalytic performance of Cd S.Therefore,in view of these two aspects,this paper focuses on the synthesis of Cd S based photocatalyst,its stability,the degree of electron and hole recombination,and the performance of photocatalytic water decomposition to produce hydrogen,and carries out the following work:（1）Cd1-x Znx S ternary co-solution nanorods were synthesized by hydrothermal method.Zinc acetate,cadmium acetate and thiourea were added into ethylenediamine-water（v:v=2:1）mixed solution,and Cd1-x Znx S ternary co-solution nanorods were produced after hydrothermal reaction.After that,the morphology and structure of the synthesized catalyst were characterized by TEM,XRD,XPS,etc.,and the fluorescence emission spectrum and 16-h four-wheel photocatalytic cycle hydrogen production test verified that the photogenerated electron and hole recombination in Cd1-x Znx S was improved,and the stability was also improved.In the performance test of photocatalytic hydrogen production,when Cd:Zn=3:7,that is,Cd0.3Zn0.7S has the highest catalytic efficiency of 5.194 mmol h-1 g-1,which is more than 1.5 times higher than the photocatalytic efficiency of Cd S.In the subsequent electrochemical impedance test,photocurrent test and nitrogen adsorption test,it is found that Cd1-x Znx S terpolymer has higher carrier transport rate,easier electron-hole pair separation and larger specific surface area than Cd S.（2）On the basis of Cd0.3Zn0.7S,the catalyst with the highest catalytic performance obtained in the first part,further improved operation was carried out.The co-catalyst Mo Se2 was synthesized by hydrothermal method from sodium molybdate and selenium powder in aqueous solution of hydrazine.Mo Se2 was placed in DMF,stripped into thin layer by ultrasonic and stirring,and was subjected to surface functionalization treatment by adding benzylamine.Finally,the treated Mo Se2cocatalyst was loaded onto the surface of Cd0.3Zn0.7S to form BA-Mo Se2/Cd0.3Zn0.7S.A series of morphology and structure characterization of the catalyst were performed by TEM,XRD,XPS,etc.,and then fluorescence emission spectroscopy and 16-h four-wheel photocatalytic cycle hydrogen production test verified that the photogenerated electrons and holes in the catalyst were less than Cd0.3Zn0.7S,which means that compared with Cd S,there was a greater improvement.And the stability is better than Cd S.In the performance test of photocatalytic hydrogen production,it was found that when the mass ratio of Mo Se2 reached 20%,the best catalytic performance was 14.05 mmol h-1 g-1,which was nearly 3 times that of Cd0.3Zn0.7S and about 7times that of Cd S.Finally,the electrochemical impedance test and photocurrent test results show that compared with Cd0.3Zn0.7S,the electron-hole pair of BA-Mo Se2/Cd0.3Zn0.7S is more easily separated and the carrier transport rate is higher.In addition,Mo Se2/Cd0.3Zn0.7S without benzylamine was prepared by the same method.Through the same series of characterization,it can be concluded that the addition of benzylamine can improve the separation of electron-hole pairs,the recombination of photogenerated electrons and holes,and the carrier transport rate.In view of the serious photoelectron-hole recombination,poor photocorrosion stability and weak catalytic ability in Cd S,this paper proposed the synthesis of terpolymer Cd1-x Znx S,and the strategy of loading Mo Se2 on the basis of Cd1-x Znx S to improve the catalytic performance and stability in the photocatalytic process.A variety of characterization methods were used to verify that the catalyst has better performance than Cd S in electron-hole pair separation and photogenerated electron and hole recombination,which provides a new idea for improving the performance of Cd S catalyst and makes a certain experimental basis. |
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