Investigation of PtNi/C as methanol tolerant electrocatalyst for the oxygen reduction reaction

Platinum-nickel electrocatalysts prepared by a simple and cost-effective procedure have been investigated for the oxygen reduction reaction (ORR) in direct methanol fuel cells (DMFCs). The formic acid method was used to deposit well-dispersed PtxNiy nanoparticles (x:y=3:2) on the surface of a carbon black support (Ketjenblack). Carbothermal reduction of the as-prepared catalyst in an inert gas (Ar) at 900 °C produced an alloy and a partial modification of the crystalline structure fromthe face centered cubic, typical of Pt, to a tetragonal structure of PtNi alloy. An acid leaching treatment was carried out to partially remove unalloyed surface nickel atoms in the outermost layers, leading to an enrichment of Pt concentration (x:y = 2:1). Cyclic voltammetry analysis in acidic mediumindicated a relatively high electrochemical active surface area (N70m2 g-1) for both untreated and thermally treated PtxNiy catalysts. The activity towards the ORR was evaluated in half-cell configuration (0.5 M H2SO4) using the rotating disk electrode technique. Similar behavior towards the ORR was found for the untreated and thermally treated PtNi/C catalysts, with an increase in activity compared to a commercial Pt/C catalyst. A remarkably better tolerance to methanol was observed for both PtNi/C cathode catalysts compared to the commercial Pt/C catalyst.