Influence of substitution of Ru on the electrocatalytic properties of the perovskite-type LaSrNiO4 electrode towards methanol oxidation

Abstract

Ru-substituted perovskite oxides with molecular formulae LaSrNi1-xRuxO4 (0.1 <= x <= 0.5) have been obtained by a modified, citric acid sol-gel route at 600 degrees C for their possible use as anodes in a direct methanol fuel cell (DMFC). These oxides have been as film on a nickel support and investigated for electrocatalysis of methanol oxidation in 1 M KOH using XRD, SEM, cyclic voltammetry, chronoamperometry, impedance and Tafel polarization. The study shows that 0.2-0.5 mol Ru substitutions improve the apparent electrocatalytic activity of the oxide towards electrooxidation of methanol; the observed improvement being the greatest (similar to 80% at E = 0.55 V versus Hg/HgO) with 0.2 mol RU substitution. During a chronoamperometric study of 5 h at E= 0.5 V in 1M KOH + 1M CH3OH, the Ru-substituted electrodes did not indicate any poisoning by the methanol oxidation intermediates/products. The methanol electrooxidation reaction follows a Tafel slope of similar to 40 mV decade(-1) and the order with respect to [OH] is 'similar to 2 on each electrocatalyst, regardless of the Ru content.