Electro-Oxidation of Borohydride on Rhodium, Iridium, and Rhodium–Iridium Bimetallic Nanoparticles with Implications to Direct Borohydride Fuel Cells

Abstract

Electrochemical oxidation of borohydride is studied on nanosized rhodium, iridium, and bimetallic rhodium–iridium catalysts supported onto Vulcan XC72R carbon. The catalysts are characterized by X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy in conjunction with cyclic voltammetry and polarization studies. The studies reveal that a 20 wt % bimetallic Rh–Ir catalyst supported onto carbon (Rh–Ir/C) is quite effective for the oxidation of borohydride. Direct borohydride fuel cell with Rh–Ir/C as the anode catalyst and Pt/C as the cathode catalyst exhibits a peak power density of at a load current density of as against at for Rh/C and at for Ir/C while operating at . The synergistic catalytic activity for the bimetallic Rh–Ir nanoparticles toward borohydride oxidation is corroborated by density-functional theory calculations using electron-localization function.