Electro-oxidation of BH4− in dimethylsulfoxide and dimethylformamide studied by rotating disk electrode voltammetry

Abstract

Borohydride (BH4−) is a promising new fuel for fuel cells, yet its practical implementation has been hindered by a deleterious hydrolysis reaction to form H2 in aqueous solvents, especially at the high BH4− concentrations necessary for high-power fuel cells. We investigated a wide array of nonaqueous solvents for their ability to hold BH4− at higher concentrations and allow effective electro-oxidation at Pt and Au, two well-studied BH4− anode materials. Only dimethylsulfoxide and dimethylformamide were found to be suitable, and precluded BH4− decomposition to H2 in bulk solution (hydrolytic or otherwise). BH4− decomposition at electrode surfaces was still observed, however. Current densities in these solvents were about an order of magnitude below those observed in aqueous solution, and onset potentials were 0.7V less favorable. MeOH addition, to stabilize oxidized states of boron, did not increase current.