Synthesis And Their Photocatalytic Hydrogen Production Of CdS-based Photocatalyst

The pollution of the atmosphere,water and soil caused by the burning of fossil fuels makes human beings face serious challenges of survival.Humans need new clean energy to reduce the use of fossil fuels.Photocatalytic hydrogen production technology is a new technology that can be developed rapidly in recent years and can use solar energy for environmental purification and energy conversion.There are many kinds of semiconductor catalysts used for photocatalystic hydrogen production.Cadmium sulfide?Cd S?,as a visible light-responsive semiconductor,has become a potential photocatalyst because of its suitable band gap width and valence band and conduction band position.However,the rapid photogenerated electron-hole recombination rate of cadmium sulfide and severe photocorrosion limit its development.Therefore,in this thesis,Cd S is taken as the research object,the non-noble metal Ni P deposited g-C₃N₄/Cd S nanocomposite is constructed by constructing a heterojunction and loading cocatalyst,and Cd S hollow nanocubes with mixed phase of Ni³⁺and S vacancies co-doping were prepared by forming special morphology,introducing defects,and controlling crystals.The specific research contents are as follows:?1?Preparation of g-C₃N₄/Cd S/Ni P nanocomposite and study on its hydrogen production performance from photolysisThe g-C₃N₄/Cd S/Ni P ternary nanocomposite was prepared by a simple co-deposition method and in-situ calcination method,which not only formed a heterojunction between g-C₃N₄ and Cd S,but also replaced the traditional precious metal cocatalyst Pt by loading a non-noble metal cocatalyst Ni P.This method overcomes the shortcomings of the previous complex steps to prepare Ni P-based ternary nanocomposites.The results show that when Ni P loading is 5%,the hydrogen production performance of g-C₃N₄/Cd S/Ni P ternary nanocomposites(1273.36?mol·h^-1·g^-1)is close to the photocatalytic production profoemance(1452.41?mol·h^-1·g^-1)of g-C₃N₄/Cd S deposited by precious metal Pt,which is 87%of its hydrogen production performance.At the same time,the g-C₃N₄/Cd S/Ni P ternary nanocomposites also showed excellent light stability.After four cycles,its performance of hydrogen production was basically unchanged.The reason why the g-C₃N₄/Cd S/Ni P ternary nanocomposite has excellent hydrogen production performance is that a heterojunction is formed between Cd S and g-C₃N₄ and Ni P as a cocatalyst can inhibit the photogenerated electron-hole recombination.?2?Preparation of Cd S hollow nanocubes and study of its photocatalytic hydrogen productionNi?OH?₂ hollow nanocubes were prepared by hard template etching,and controllable mixed-phase Cd S hollow nanocubes with the co-doping of Ni³⁺and S vacancy were obtained by anion exchange and cation exchange.In the cation exchange process,the nickel ions in the precursor nickel sulfide are replaced with cadmium ions,the doping amount of Ni³⁺can be adjusted by controlling the reaction time of the cation exchange,and the concentration of S vacancies can be controlled by controlling the amount of cadmium ions added.The results prove that the Cd S hollow nanocube exhibits excellent photocatalytic hydrogen production performance and photostability.When the cation exchange reaction time is 3 h and the molar ratio of sulfur and cadmium is 1:1.5,the hydrogen production performance of the Cd S hollow nanocube(2257.38?mol·h^-1·g^-1)is the highest,which is 8 times of the bulk Cd S nanoparticles(286.41?mol·h^-1·g^-1).After ten cycles of photostability testing,the hydrogen production performance of photocatalytic can still maintain the original 89%.This is because the hollow cubic structure of Cd S can increase the absorption of visible light,the presence of the mixed crystal phase can promote the separation of photogenerated electrons-holes,and the co-doping of Ni³⁺and S vacancy can capture photogenerated electrons,thereby extending the life of photogenerated electrons and inhibit photogenerated electron-hole recombination.