On the synthesis of RuSe oxygen reduction nano-catalysts for direct methanol fuel cells

Abstract

Oxygen reduction reaction has a crucial role in energy conversion systems such as fuel cells. State-of-the-art Pt-based cathode catalysts suffer from low efficiency which is severely affected by poisoning of methanol fuel crossing the membrane that separates the electrodes and high cost. We have synthesized a non-platinum RuSe 3–15-nm in size catalysts using microwave irradiation technique, which produces nanomaterials at high efficiency and short time spans. Several Ru/Se atomic ratios of RuSe were prepared using both elemental Se powder and H2SeO3 as precursors. The structure and composition of the obtained materials were characterized using XRD, EDX, ICP-OES, and DSC/TGA. Electrochemical study of oxygen reduction reaction (ORR) on these catalysts was conducted using rotating disk electrode (RDE) technique, from which the Tafel slopes and exchanged current densities of ORR were calculated. The use of H2SeO3 as the Se source provides catalysts with controlled composition. All obtained materials show good electrocatalytic activity towards oxygen reduction and maintain high activity in the presence of high methanol contamination. A rigorous kinetic study of ORR on RuSe catalysts show that at Ru to Se ratio is 2 to 1, and the highest kinetic currents are attained. Stability tests at 0.4 V in strong acidic conditions and elevated temperatures, for over 600 hours, exhibit no degradation.