Preparation And Photocatalytic Activities For Hydrogen Evolution Of Cu Nanoparticles/Few Layers Graphene

Energy crisis and environmental deterioration are very serious problems,but the growing development of photocatalytic hydrogen production technology has opened up a new way to solve them.The photocatalyst in the traditional sense is a semiconductor catalyst,and recent research has found that metal nanoparticles?NPs?such as Au,Ag,Cu,etc,it can also be used for photocatalytic hydrogen production by its surface plasmon resonance effect?SPR?in the absence of a semiconductor catalyst.Cu is favored in the field of photocatalytic hydrogen production because of its abundant reserves on the earth and cheap metals.However,pure Cu NPs show poor chemical stability and easy to reunite.Therefore,a simple strategy was considered to obtain stable binary composite containing stable Cu NPs in order to promote the formation of H₂.Graphene has attracted much attention due to its large specific surface area,great optical transmittance,excellent conductivity and rapid carriers mobility at room temperature.Therefore,we choose to use graphene as a carrier of Cu NPs.The use of a wide range of biomass as a precursor to obtain graphene has been extensively studied for its low cost and simple process.In view of this,this paper constructs a Cu/graphene composite catalyst system for photocatalytic decomposition of water to produce H₂.The synthesis of composite photocatalyst Cu/graphene and its photocatalytic hydrogen evolution were reported in this paper.The conclusion is as follows:?1?The graphene with wrinkles,few layers and specific defects was prepared from low viscosity chitosan as a precursor by low carbonization temperature and high temperature activation.At an optimum activation temperature of 1100°C,the obtained CG-1100 had a specific surface area of 1212 m²/g and a total volume of 1.02 cm³/g.Characterization results of Raman,SEM,XRD,AFM,etc.indicated that CG-1100 is a successfully graphene.which was similar to the another two graphenes containing less defects,namely graphene nanosheets?GNP?and multilayer graphene powder?MGP?.?2?Subsequently,under the condition of lactic acid as a sacrificial agent,Cu/CG-1100composite photocatalyst was prepared by in-situ synthesis by mixing CG-1100 and Cu?Ac?₂solution under illumination,and the hydrogen production was detected online.The SEM,TEM,XRD and XPS characterizations indicated that Cu/CG-1100 was successfully synthesized.Subsequently,the effect of the copper content of the binary complex on hydrogen evolution was investigated,and the copper content was 1wt%,5wt%,10wt%,15wt%,and20wt%,respectively.When the binary composite contains 10wt%Cu NPs,the hydrogen evolution rate of Cu/CG-1100 reaches 3.94 mmol/?g·h?,which is 3.2 times that of pure Cu NPs.?3?In addition,the study also found that the degree of defect of graphene can affect the rate of photocatalytic hydrogen production.By depositing the same theoretical content of Cu NPs on GNP and MGP,their hydrogen production rate were 2.34 mmol/?g·h?and 2.18 mmol/?g·h?,respectively,which were lower than Cu/CG-1100.The results show that the more defects on graphene,the higher rate of photocatalytic hydrogen evolution.?4?We got a good hydrogen production effect on Cu/CG-1100 by photocatalytic cycle stability test under 36h illumination.Subsequently,we discussed the hydrogen production mechanism of the catalyst and provided theoretical support for further exploration of the catalyst system.