The enhancement effect of tungsten on the kinetics of oxygen reduction at novel RuSeW electrocatalysts

摘要

In order to improve the performance of direct methanol fuel cells, carbon-supported RuSeW nano-electrocalalysts were prepared using an impregnation method with RuO2, SeO2 and WO2 as precursors. The novel electrocatalyst was evaluated for oxygen reduction in 0.5 M H2SO4 media in half cells, either as a gas diffusion electrode or as an ink-type rotating disk electrode. The most striking feature was that the tungsten participation significantly enhanced the kinetics of oxygen reduction, exhibiting greater apparent rate constants (up to 35%) and lower apparent activation energy (15% less) than those at the RuSe cathode. The oxygen reduction on the RuSe W electrode was a first-order reaction with respect to oxygen with the Tafel slopes of -0.07 and -0.12 V dec(-1) at high and low potential regions, respectively. The enhancement effect was corroborated in direct methanol fuel cells. The electrochemical impedance spectra obtained in situ of fuel cells displayed reduced ohmic and cathode activation resistances as a consequence of the tungsten modification. The electrocatalytic effect was related to a change in the electrocatalyst structure, which was discussed based on the SEM and XRD data.