Preparation Of ZnCdS Nanocages From ZIF-8 Framework For Efficient Photocatalytic Hydrogen Production

In order to solve the increasingly prominent problems of environmental pollution and energy crisis,people are looking for sustainable new energy sources day and night,and have successfully developed emerging energy such as solar energy,wind energy,biomass energy,tidal energy,geothermal energy,hydrogen energy and nuclear energy.Among many emerging renewable energy sources,solar energy is inexhaustible and is considered to be one of the most promising new energy sources.Therefore,it is urgent to develop a technology that can convert solar energy into chemical energy that can be easily stored and transported.Among them,semiconductor photocatalysis technology can convert solar energy into clean hydrogen energy（H₂）by splitting water.This technology provides a feasible way for the sustainable utilization of solar energy.Zinc cadmium sulfur solid solution（ZnCdS）has attracted much attention due to its excellent visible light rate,tunable band gap and controllable morphology.This semiconductor material can achieve highly active photocatalytic hydrogen production by adjusting the ratio of Zn/Cd,and is considered to be one of the best photocatalytic materials.In this work,the problems of rapid electron-hole pair recombination and poor stability of photocatalytic reaction of a single ZnCdS solid solution photocatalyst were optimized,and the morphology and size of nanocages were studied in depth by using various characterization methods and photocatalytic hydrogen evolution experiments.Effects of design and different Zn/Cd ion contents on the hydrogen production performance of ZnCdS solid solution materials and the effect of RF coating on the stability and photocatalytic performance of ZnCdS（RF）hollow nanocages photocatalysts.The specific research contents are as follows:1.ZIF-8 precursor was synthesized by using zinc nitrate and 2-methylimidazole as raw materials.ZIF-8 template with optimal specific surface area was obtained by adjusting the molar ratio of different zinc nitrate and 2-methylimidazole to obtain different grain sizes.On the basis of ZIF-8 template,S ion was introduced into the template by solvothermal method.Zn S not only broadened the visible light absorption range of ZIF-8 precursor,but also greatly promoted the absorption efficiency of light.Cd ions were introduced by cation exchange method.The ZnCdS hollow nanocages photocatalysts with different Zn/Cd ion contents were designed and used for solvothermal reaction of Zn S nanocage materials with Cd Cl₂ at different times,and the hydrogen production data were compared through the photocatalytic hydrogen evolution reaction,in order to obtain the best production.2.The ZnCdS hollow nano-cage photocatalyst with the best hydrogen production activity was subjected to RF coating treatment.In order to explore the effect of RF coating on the hydrogen production efficiency and stability of ZnCdS,we tested the photocatalytic hydrogen production performance of RF-coated and non-RF-coated ZnCdS.The hydrogen evolution rate of the ZnCdS（RF）nanocages is as high as 21.74mmolh^-1g^-1,which is 8.3 times that of the non-RF-protected ZnCdS product,and the ZnCdS（RF）photocatalyst has excellent stability,which has been tested for many times.Its hydrogen evolution activity has no obvious decline.The hollow-structured solid solution with RF layer coating has better crystallinity and less defects under the reaction at higher temperature,which can significantly accelerate the separation and transfer of charges,from promoting the reaction forward.The introduction of RF can suppress the collapse and polycondensation of the material structure during the vulcanization reaction and ion exchange process,and can also maintain the structural stability of the ZnCdS nanocages in the photochemical reaction,thereby effectively preventing the performance degradation.Significantly increases the stability of the material.