Se-modified Ru nanoparticles as ORR catalysts: Part 2: Evaluation for use as DMFC cathodes

The synthesis, electrochemical analysis, and hydrogen-air fuel cell testing results for a new type of Se/Ru catalyst called Se/Ru(aq) were described in Part 1. In this second report, we present methanol tolerance studies and direct methanol fuel cell testing for the same catalyst. A “methanol-tolerant” catalyst does not oxidize methanol, nor becomes depolarized by its presence, which is a desirable property for DMFC cathodes used with methanol-permeable membranes or in mixed-reactant designs. In perchloric acid electrolyte, the Se/Ru(aq) catalyst was found to be highly tolerant to 1.0 M methanol. More importantly, in fuel-cell testing as a DMFC cathode, Se/Ru(aq) was shown to be highly tolerant to methanol crossing through the membrane (from the anode side) up to a feed concentration of 17 M. The results were compared to those obtained using unmodified Ru black and Pt black at the DMFC cathode, in order to gain insight into the catalyst function and to compare the performance to relevant benchmarks. Compared to Pt cathodes, the performance of Se/Ru(aq) is significantly better at high methanol concentrations (e.g., 17 M), suggesting their use either in DMFCs with high methanol feed concentrations or in mixed-reactant fuel cells.