Highly active Pt_xPd_y/SnO₂/C catalyst for dimethyl ether oxidation in fuel cells

Dimethyl ether (DME) is a nontoxic gas that is considered a potential fuel for direct-feed proton exchange membrane fuel cells (PEMFCs). DME has several advantages over other fuels, including high energy density, pumpless fuel delivery, liquefied storage, low toxicity and minimal crossover through Nafion^® membranes in PEMFC. However, the low activity of the state-of-the-art catalyst (Pt₅₀Ru₅₀) for DME oxidation is the main hurdle in the development of efficient fuel cell devices. In this work, fine layers of SnO₂ on high surface-area carbon (Pt_xPd_y/SnO₂/C) catalysts were synthesized by ethylene glycol-assisted reduction and characterized by X-ray diffraction, TEM, EDX, XPS, and ICP-OES. The electro-oxidation of DME was systematically studied in a conventional three-electrode cell and a laboratory prototype direct DME fuel cell (DDMEFC) operating at 70 °C. Compared to other catalysts reported for DME oxidation, the Pt_0.75Pd_0.25/SnO₂/C shows higher specific power density in both the conventional three-electrode cell and the fuel cell configurations. The peak power density delivered by direct gas feed DDMEFCs is 110 mW cm^-2 at 0.4 V with only 1.2 mg cm⁻² of platinum group metal (PGM) loading.