Preparation Of High Performance ZnCdS-based Photocatalysts And Hydrogen Evolution Study

With the rapid development of social science and technology,the consumption of energy demand increases sharply,meanwhile,resulting in serious environmental pollution.Therefore,human beings focus on seeking and developing new energy.Hydrogen energy is an ideal energy resource with high energy density and environmental friendliness.There are many methods to obtain hydrogen,such as fossil energy cracking,electrocatalysis,photo（electro）catalysis.In these methods,photocatalytic hydrogen evolution by water splitting has attracted researchers due to its cheap and convince.However,the light conversion efficiency is less than 1%due to photocatalyst intrinsic drawbacks.So,developing highly efficient photocatalysts is an important research direction.Transition metal sulfide（TMD）is a kind of very efficient photocatalyst,among which zinc cadmium sulfide solid solution is a kind of photocatalyst with great application prospect.However,serious photo-corrosion,carrier recombination and narrow visible light absorption seriously hindered its practical application.Therefore,it is important to improve photo-stability,carrier separation efficiency and light absorption range.In this paper,loading holes co-catalyst and construction heterojunction were used to modification Zn_0.5Cd_0.5S.XRD,SEM,XPS,TEM and other characterization methods are used to analyze the chemical composition and morphology.Finally,the photocatalytic performances are evaluated by electrochemical experiments and photocatalytic hydrogen evolution tests.（1）Zn_0.5Cd_0.5S was modified withγ-NiOOH andβ-NiOOH by in-situ second hydrothermal.Meanwhile,loading differentγ-NiOOH loading mass composite photocatalyst was prepared and characterized photocatalysis hydrogen evolution properties.Through these results,the hydrogen evolution rate ofγ-NiOOH/ZnCdS-100 is highest,up to 48.6 mmol/g·h.It is 10.8 times higher than pristine ZnCdS（4.50 mmol/g·h）,and the apparent quantum yield is up to 18.23%（400 nm）.Meanwhile,the photo-respond current is 3.39μA/cm²,1.8 times of pure ZnCdS,and carriers transfer resistance sharp decreasing.And life-time increase from5.50 ns（ZnCdS）to 6.10 ns（γ-NiOOH/ZnCdS-100）.（2）Hollow ZnCdS nano-flower were prepared by hydrothermal method,and then CuPc molecules were grown on the surface of the ZnCdS nanospheres by solution method.The amorphous CuPc covered on ZnCdS sphere surface,forming a hollow core-shell structure.Under visible light irradiation,the photocatalytic hydrogen evolution rate of loading 4%CuPc is up to 29.2 mmol/g·h,3.5 times bigger than pristine ZnCdS（8.4 mmol/g·h）.Meanwhile,the apparent quantum yield is 6.95%（400 nm）.The lifetime is 1.05s after loading CuPc,which is calculated from transient open-circuit voltage.And the transient photo-current is 4μA/cm²,3times of pure ZnCdS（1.3μA/cm²）.Meanwhile,the carriers transfer resistance decrease three times.This structure can not only increase light absorption,but also accelerate carriers separation and transfer.（3）Bulk-heterojunction of CuNi₂S₄ and ZnCdS was prepared by one-step hydrothermal.The CuNi₂S₄ nano-particles are uniformly dispersed in ZnCdS phase.Therefore,the contact interface of two phases enhances greatly,which can effectively accelerate carriers transport and photocatalysis properties.Through adjust adding molar ratio of copper source and nickel source,CuNi₂S₄/ZnCdS composites photocatalysts were prepared.When the molar ratio of CuNi₂S₄ is3%,the photocatalysis hydrogen evolution rate is highest,up to 33.87 mmol/g·h,10 times of ZnCdS（3.37 mmol/g·h）.Meanwhile,the apparent quantum yield is up to 16%（400 nm）.Due to the excellent electrocatalysis property of CuNi₂S₄,the HER over-potential decrease obviously and carriers transfer resistance decrease an order of magnitude.Through construction bulk-junction,the photocatalysis property enhances greatly due to larger heterojunction interface formation.The photo-response current of ZCS-CNS-3%is up to 57.1μA/cm²,4.35times of pristine ZnCdS（13.1μA/cm²）.