Electrochemical benzene hydrogenation using PtRhM/C (M = W, Pd, or Mo) electrocatalysts over a polymer electrolyte fuel cell system

Electrochemical hydrogenation of benzene to cyclohexane was studied over carbon-supported Pt and Pt-based alloy catalysts (e.g., Pt/C, Pt4Rh1/C, Pt4Rh0.75W0.25/C, Pt4Rh0.75Mo0.25/C, and Pt4Rh0.75Pd0.25/C), which were prepared using a borohydride reduction method combined with a freeze-drying procedure. The Pt4Rh0.75W0.25/C catalyst showed the best performance for the electrochemical hydrogenation of benzene to cyclohexane over a proton exchange membrane fuel cell (PEMFC) system. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to investigate structural modifications on the Pt-based catalysts, in which the carbon-supported Pt-based binary and ternary catalysts indicated effective alloy formation with decreased lattice parameters as compared to Pt/C. X-ray photoelectron spectroscopy (XPS) and X-ray absorption-near-edge spectroscopy (XANES) were also carried out to characterize electronic features of the Pt-based alloy catalysts, in which both the structural and electronic modifications were closely associated with the benzene hydrogenation activities.

In this study, we have investigated the electronic and structural properties of Pt/C, Pt4Rh1/C, or Pt4Rh0.75M0.25/C (M = Mo, Pd, and W) catalysts for the electrochemical hydrogenation of benzene to cyclohexane. The Pt4Rh0.75W0.25/C catalyst showed a superior performance in the benzene hydrogenation, which may be associated with modifications in structural lattice parameter and electronic 5d-orbital vacancy compared to the other Pt-based binary or ternary catalysts tested here.Figure optionsDownload as PowerPoint slide