Effect of Rh content on carbon-supported PtRh catalysts for dehydrogenative electrooxidation of cyclohexane to benzene over polymer electrolyte membrane fuel cell

摘要

Electrochemical dehydrogenative oxidation of cyclohexane to benzene was studied over carbon-supported PtRh(PtRh/C)electrocatalysts,which were prepared with different Pt:Rh atomic ratios from 4:1 to 1:4 using a borohydride reduction method combined with freeze-drying procedure at room temperature.The bimetallic PtRh/C catalysts were characterized by various physicochemical analyses such as X-ray diffraction(XRD),transmission electron microscopy(TEM),and X-ray absorption-near-edge spectroscopy(XANES).The variation of Rh content over the PtRh alloy formation caused significant structural and electronic modifications on the catalyst phase,which could be associated with consistent changes in electrocatalytic activities over a polymer electrolyte membrane(PEM)fuel cell.The Pt4Rh1/C catalyst as the anode electrocatalyst showed a maximum power density of ca.8.5 mW cm~(-2).Here,both the structural modification via lattice parameter change and the electronic modification through charge transfer from Rh to Pt could kinetically facilitate the sluggish electrode reaction with an increased exchange current density on the dehydrogenative electrooxidation of cyclohexane to benzene over the PtRh/C anodes of cyclohexane fuel cell.