Preparation Of Graphene-based Composite Materials And Their Application For Oxygen Reduction Reaction

With the growing demand for fossil fuels and increasing environmental problems from burning fossil fuels in recent years,finding clean and new energies has become a hot topic.Due to the low or zero emissions,fuel cells have attracted enormous attention.The oxygen reduction reaction（ORR）plays an important role in fuel cells.However,the ORR kinetics at the cathode is very slow,so a electrocatalyst is needed to accelerate the kinetics.High electrical conductiviy,large surface and chemical stability of reduced graphene oxide（rGO）makes it to be an excellent substrate for the ORR catalysts.In this work,we demonstrate the synthesis of ZnFe₂O₄/rGO nanohybrids by a one-pot hydrothermal strategy at different mass ratios by using rGO as the support.The surface morphology and chemical composition of ZnFe₂O₄/rGO are characterized by scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,X-ray diffraction（XRD）,X-ray photoelectron spectroscopy（XPS）,thermogravimetric analysis（TG）and Fourier transform infrared spectroscopy（FTIR）.Cyclic voltammetry（CV）,linear sweep voltammetry（LSV）and chronoamperometry are used to evaluate the electrochemical activities and stabilities of ZnFe₂O₄/rGO catalysts in alkaline media.CuCo₂S₄ nanoparticles supported on rGO were prepared by hydrothermal method with different mass ratios.SEM,TEM,EDS and XPS are used to investigate the morphology and chemical composition of CuCo₂S₄/rGO.CV and LSV are used to evaluate the electrochemical activities of CuCo₂S₄/rGO.The stability and the ability against methanol crossover of CuCo₂S₄/rGO are also investigated.We demonstrate,for the first time,the synthesis of 3D NS-rGO supported with CuFeS₂（CuFeS₂/3D-NS-rGO）as a novel electrocatalyst for ORR via a facile way.The chemical composition and surface morphology of the CuFeS₂/3D-NS-rGO are characterized by XRD,XPS,SEM and TEM.CV,LSV and chronoamperometry are usedtoevaluatetheelectrochemicalactivitiesandstabilitiesofthe CuFeS₂/3D-NS-rGO catalysts in alkaline media.The CuFeS₂/3D-NS-rGO shows excellent activity and much superior methane tolerance and better durability than the commercial Pt/C catalyst,and the catalyzed reaction follows a desirable four-electron pathway in alkaline media.