The development of the alkaline anion exchange membrane (AEM) for the direct liquid fuel cell opened up opportunities for the use of new fuels (that oxidized inefficiently in PEM fuel cells) and new catalysts (that corroded easily in PEM fuel cells).  The first fuel studied in depth was ethanol because it oxidizes much more efficiently in alkaline media than acidic media.  However, the same palladium catalyst that oxidizes ethanol in alkaline media can also be used to oxidize several other alcohol fuels including polyalcohols such as ethylene glycol (EG), propylene glycol (PG), and glycerol (G).  Therefore, we recently demonstrated a flexible fuel direct liquid fuel cell that operated on alcohols such as ethanol, EG, PG, and G. However, these fuels all oxidize more slowly then ethanol, requiring significant kinetic improvement to be used practically.

We tested various combinations of Pd:Cu and compared them in each polyalcohol fuel, EG, PG, and G.  We observed that any quantity of Cu added to the Pd produced an increase in oxidation rate compared with pure Pd for all three polyalcohol fuels.  We also observed a down-shift in d-band center as observed by XPS.  We hypothesize that the addition of Cu to the Pd results in a combination of the electronic and bifunctional effects.  The electronic effect is caused by perturbations in the electronic structure of Pd, the primary catalyst, induced by the Cu. The bifunctional effect is caused by the co-catalysis of Pd and Cu directly on the surface of the catalyst.