The Synthesis Of Cadmium Sulfide-based Photocatalytic Materials And The Performance Of Photolysis Of Water To Produce Hydrogen

The control and governance of environmental pollution is a major problem that human beings face and urgently need to solve.It is imperative to find new clean energy and effective technology to control the environment.Semiconductor photocatalysis technology provides us with an important method to directly convert solar energy and effectively control environmental pollution.However,although many catalysts have been found,which having photocatalytic hydrogen production ability,their energy conversion rate is very low,and the amount of hydrogen production is small,which is not practical.In order to obtain a catalyst with higher catalytic hydrogen production efficiency,the synthesis of cadmium sulfide-based photocatalytic materials and the hydrogen production performance of photolysis water were studied.As a photocatalyst,CdS nanorods and ZnCdS nanoparticles have narrow band gaps,which make electron holes easy to recombine,and the photostability is relatively poor.It is prone to photocorrosion under long-term illumination reaction.Based on these drawbacks,we modify the photocatalyst by means of a composite method.In the choice of cocatalyst,precious metal materials are good in performance,but lack of resources,expensive chrome and other factors make them impractical.It has been proved by experiments that oxide WO3,carbide Mo2C,bimetal nitride Ni2Mo3N,boride NiB,transition metal iron and sulfide MoS2 are not only cheap to produce,but also can be used as a cocatalyst to achieve hydrogen production better than noble metals.Therefore,we have successfully prepared WO3/ZnCdS,Mo2C/ZnCdS,Ni-2Mo3N/ZnCdS,NiB/ZnCdS,Fe/CdS,MoS2/CdS,which are six kinds of photocatalysts with good hydrogen production performance.In this experiment,two preparation methods of hydrothermal synthesis and temperature-programming are mainly adopted.The process is simple and low-cost,and is hanmless to the human body and the environment.The surface morphology and optical properties of each catalyst were investigated by X-ray powder diffraction(XRD),scanning/transmission electron microscopy(SEM/TEM),X-ray photoelectron spectroscopy(XPS)and UV-Vis absorption spectroscopy(UV-Vis)characterization.The effects of different amounts of cocatalyst on the photocatalytic activity of the main catalyst ZnCdS or CdS were investigated,among which 35 wt.%WO3/ZnCdS,12 wt.%Mo2C/ZnCdS,15 wt.%Ni2Mo3N/ZnCdS?15 wt.%NiB/ZnCdS,30 wt.%Fe/CdS,30 wt.%MoS2/CdS had the best hydrogen production activity,and their hydrogen production amounts were 98.68,55.43,53.65,77.63,327.85,and 244.44 umol/mg,respectively.The mechanism of the composite photocatalysts were investigated by fluorescence emission spectroscopy(PL),alternating current impedance spectroscopy and photocurrent measurement.When the catalyst is excited by enough photons under illumination,the electrons undergo a transition from the valence band to the conduction band,and the photogenerated holes accumulate on the more negative valence band.The cocatalyst can be used as an electron donor to receive and transfer electrons,so that the electrons contributed by the cadmium sulfide-based photocatalytic material can be rapidly transferred to produce H2 by reducing reaction with H2O.At the same time,the hole sacrificial agent L-lactic acid in the system consumes electrons to generate pyruvic acid and hydrogen.These can effectively separate the photogenerated electron-hole pairs inside the catalyst to achieve excellent photocatalytic performance.