Kinetics and electrocatalytic activity of nanostructured Ir-V/C for oxygen reduction reaction

Active carbon-supported Ir-V nanoparticle catalysts have been synthesized by an ethylene glycol reduction method under controlled conditions at pH 10-13 and 120 C then further reduced at elevated temperature from 150 to 500 C using IrCl3 and NH4VO3 as the Ir and V precursors The nanostructured catalysts have been characterized by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (TEM) Ir nanoparticles after modification with V show a narrow particle size distribution in the range 0 5-4 5 nm centered at 1 8 nm and are uniformly dispersed on Vulcan XC-72 No particle agglomeration was observed not even at high V loadings (V Ir = 4 1 in atomic ratio) Investigation of the catalytic activity of the Ir-V/C by means of cyclic voltammetry (CV) and linear sweep voltammetry (LSV) employing a rotating disk electrode (RDE) has revealed that the presence of V may suppress the electrochemical oxidation of Ir and stabilize the Ir active centers About six times higher kinetic current density was obtained for Ir-V/C compared to that of the pure Ir/C catalyst at 0 8V versus RHE for the oxygen reduction reaction (ORR) The ORR in acid solution proceeds by an approximately four-electron pathway through which molecular oxygen is directly reduced to water The performance of a membrane electrode assembly (MEA) prepared with the most active 40% Ir-10% V/C as the cathode catalyst in a single proton-exchange membrane fuel cell (PEMFC) generated a maximum power density of 517 mW cm(-2) at 0 431 V and 70 C and 100 h of stable cell operation due to no loss of catalyst sites on the cathode (C) 2010 Elsevier Ltd All rights reserved