Graphene-Supported Substoichiometric Sodium Tantalate as a Methanol-Tolerant, Non-Noble-Metal Catalyst for the Electroreduction of Oxygen

For the oxygen reduction reaction (ORR) in acidic medium, a good combination of an active and stable catalyst highly dispersed on a conductive and durable support is required. Moreover, for direct methanol fuel-cell applications, a suitable tolerance to methanol poisoning is also necessary. In this communication, we report on a new graphene-supported sodium tantalate (Na2Ta8O21-x) electrocatalyst obtained at high temperature and characterized by significant substoichiometry. The synthesis includes the precipitation of tantalum oxide on a high surface area graphene and subsequent thermal treatment at 900 degrees C. A novel sodium tantalate phase with oxygen vacancies is thereafter obtained. This catalyst formulation shows promising activity towards the ORR especially in the presence of a high methanol concentration, as evidenced by a high tolerance to methanol poisoning. Accelerated stress tests and chemical leaching experiments also show the remarkable stability of the catalyst. This material presents good perspectives for application in cost-effective fuel cells.