Harnessing dimethyl ether and methyl formate fuels for direct electrochemical energy conversion

Abstract

In this work, the oxidation of a mixture of dimethyl ether (DME) and methyl formate (MF) was studied in both an aqueous electrochemical cell and a vapor-fed polymer electrolyte membrane fuel cell (PEMFC) utilizing a multi-metallic alloy catalyst, Pt3Pd3Sn2/C, discovered earlier by us. The current obtained during the bulk oxidation of a DME-saturated 1 M MF was higher than the summation of the currents provided by the two fuels separately, suggesting the cooperative effect of mixing these fuels. A significant increase in the anodic charge was realized during oxidative stripping of a pre-adsorbed DME + MF mixture as compared to DME or MF individually. This is ascribed to greater utilization of specific catalytic sites on account of the relatively lower adsorption energy of the dual- molecules than of the sum of the individual molecules as confirmed by the density functional theory (DFT) calculations. Fuel cell polarization was also conducted using a Pt3Pd3Sn2/C (anode) and Pt/C (cathode) catalysts-coated membrane (CCM). The enhanced surface coverage and active site utilization resulted in providing a higher peak power density by the DME + MF mixture-fed fuel cell (123 mW cm−2 at 0. 45 V) than with DME (84 mW cm−2 at 0.35 V) or MF (28 mW cm−2 at 0.2 V) at the same total anode hydrocarbon flow rate, temperature, and ambient pressure.