Selective Borohydride Oxidation Reaction on Nickel Catalyst with Anion and Cation Exchange Ionomer for High-Performance Direct Borohydride Fuel Cells

Direct borohydride fuel cells (DBFCs) operate with liquid H2O2 and a high-energy-density NaBH4 solution. A facile, direct synthesis method using a non-noble nickel catalyst for the DBFC anode is shown. The complex anode reaction with an anion-exchange ionomer (AEI) and a cation-exchange ionomer (CEI) is evaluated in half-cell and single-cell configurations. The ionomer type produces high (AEI) or low local pH (CEI) at the active site of the catalyst in the single-cell configuration, generating different catalytic reactions. The performance of the nickel catalyst is compared to that of a palladium catalyst. The selective catalytic activities for the borohydride oxidation reaction and hydrogen oxidation reaction are the key parameters for achieving good performance. Furthermore, fuel utilization and H-2 evolution measurement in a single-cell configuration provide more information on the complex anode reaction in the DBFC. The nickel catalyst with CEI on nickel foam (NiF@CEI-Ni) shows the highest DBFC peak power density (0.59 W cm(-2)) with a non-noble metal anode catalyst.