Effect of oxidative heat-treatment on electrochemical properties and oxygen reduction reaction (ORR) activity of Pd–Co alloy catalysts

Pd–Co catalysts of various compositions are subjected to heat-treatment in an oxygen-containing atmosphere (5% oxygen and 95% argon by volume) and the catalysts are found to form oxides. On exposure to electrochemical conditions, the oxides get reduced in the potential range of 0.05–0.4 V of the voltammogram and the voltammetric features of the heat-treated catalyst are comparable to that of the corresponding as-prepared catalyst of same composition. The trends in electrochemical surface area (ESA), current due to formation of adsorbed-oxygenated species and activity towards oxygen reduction reaction (ORR) with catalyst composition are similar and they are in the order of Pd ≪ Pd1.5Co < PdCo < Pd6.3Co < Pd2Co < Pd3Co. The ORR activity of the catalyst subjected to the oxidative thermal treatment is higher than that of Pd and the corresponding as-prepared catalyst of same composition.