Design,Synthesis And Electrical(Photo)Catalytic Performance Of Transition Metal-containing(M=Pt,Au,Cu,Zn)/Graphene Composite Catalysts

In this paper,two-dimensional graphene was used as support materials to combine metal oxides（V₂O₅）or plasma-excited Au with Pt to construct novel Pt-based catalysts.The effects of catalysts’components and morphologies on their catalytic performance towards methanol oxidation reaction（MOR）,oxygen reduction reaction（ORR）and hydrogen evolution reaction（HER）were systematically investigated,and the significant enhancement of catalytic performance of MOR,ORR and HER deriving from electro-photo synergistic catalytic effect was also discussed.In addition,Cu,metal oxide（ZnO）and graphene are combined to synthesize Cu-ZnO/graphene composites which are used to catalyze reduction of carbon dioxide（CO₂）.The main research results are as follows:1.Three kinds of catalysts are synthesized with different methods as follows:（1）Pt-Au/GNs composites were synthesized by synchronous microwave reduction method.（2）Pt-V₂O₅/PGNs composite was synthesized by one-pot high temperature solid phase method.（3）Cu-ZnO/GNs composite was synthesized by high temperature solid phase method.The composition,structure and morphology of as-synthesized composites were characterized by XRD,XPS,ICP,SEM,Raman,TEM and HAADF-STEM.The results demonstrate that:（1）The dispersion of Au nanoparticles in Pt-Au/GNs is closely related with its Au content.When the content of Au added is low,the Au nanoparticles are evenly distributed,forming a heterojunction structure with Pt nanoparticles,however,with the increasing amount of Au,Au nanoparticles aggregate into larger particles;（2）In Pt-V₂O₅/PGNs composite using V₂O₅ as the precursor,only a small amount of V₂O₅ was reduced to metallic V to form Pt-V alloy with Pt,while most of V₂O₅ existed in the form of V₂O₅ state.Additionally,P was successfully doped into graphene with PPh₃ as the precursor.（3）Cu-ZnO/GNs composite was synthesized in the presence of Cu²⁺and Zn²⁺precursors,to exhibit a thin flake morphology,however,in the absence of Cu species,ZnO converted from a precursor of Zn²⁺will volatilize due to the volatilization under high temperature,which demonstrates that the strong interaction between Cu and ZnO in the Cu-ZnO/GNs is in favor of inhibiting the loss of ZnO.Cyclic voltammetry（CV）,linear sweep curve（LSV）,chronoamperometry（IT）,Tafel curve and other electrochemical methods were used to study the electrocatalytic and electro-photo catalytic properties of different composites.The results show that:（1）The catalytic performance of Pt-Au/GNo for MOR and ORR is affected by the Pt:Au ratio.Pt-Au/GNs（Pt:Au=1:0.1）with lower Au content has good dispersion,excellent electron transfer ability and CO tolerance,exhibiting superior electrocatalytic activity and stability for MOR and ORR,but excessive Au can aggregate into larger particles,which is not beneficial to their electrocatalytic activity.However,under simulated sunlight irradiation,Pt-Au/GNs with higher Au content can exhibit better electro-photo catalytic activity for MOR and ORR due to the effective SPR of Au nanoparticles;（2）P-doped GNs in Pt-V₂O₅/PGNs causes more defects on the graphene surface to promote the deposition and dispersion of Pt-based nanoparticles,providing more active sites for catalysis.Better conductivity of P-doped GNs also contribute to its better electrocatalytic performces.Moreover,the good photo-responsive property of V₂O₅ endows Pt-V₂O₅/PGNs with good electro-photo synergistic catalytic performance both towards ORR and HER under simulated sunlight;（3）Cu in Cu-ZnO/GNs acts as a dispersive catalytic center to enrich multiple oxygen vacancies to its adjacent positions,resulting in a efficient catalytic active site.And the introduction of ZnO can bring about the strong metal-support interactions and enhance the catalytic efficiency of Cu metal.So the synergistic effect between Cu and ZnO is in favor of the strong adsorption and activation of CO₂ molecule and to gradually reduce CO₂ into CH₄.The results in this work will provide a new strategy and some theoretical and experimental evidences for exploring the novel and efficient electrocatalysts used in green energy conversion and utilization.