Tunable compositions of Pd100-xCux catalysts towards the electrooxidation of ethanol and ethylene glycol

We present here an extensive study on the electrocatalytic activity of varying compositions of Pd100-xCux (100 <= x <= 0) catalysts towards the electrooxidation of ethanol and ethylene glycol (EG). The Pd100-xCux catalysts were electrochemically synthesized and characterized by field-emission scanning electron microscopy, energy-dispersive X-ray analysis, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. Electrochemical investigations were carried out by means of cyclic voltammetry, linear sweep voltammetry and chronoamperometry studies in 1 M KOH and the respective alcohols. The electrocatalytic activity of the Pd100-xCux catalysts was quantified by their mass activity (mA mg(-1)) and onset potential (V vs. RHE). It turned out that the catalysts Pd90Cu10, Pd80Cu20 and Pd70Cu30 exhibited enhanced activity compared to pristine Pd for both the alcohols. On the other hand, the Pd60Cu40 and Pd samples exhibited a similar performance towards ethanol oxidation implying possible attractive substitution of 40% Pd with Cu, which will remarkably reduce the cost of the Pd electrocatalyst for direct alcohol alkaline fuel cell applications. For EG oxidation, the Pd80Cu20 and Pd70Cu30 catalysts exhibited stable performance accompanied by high mass activity. The combined effects of electronic coupling between Pd and Cu and the preferential oxophilicity of copper in the PdCu alloy are ascribed to be responsible for such an enhanced electrocatalytic activity.