Nickel Metal Nanoparticles as Anode Electrocatalysts for Highly Efficient Direct Borohydride Fuel Cells

Developing cost-effective electrocatalysts for the multielectron borohydride oxidation reaction (BOR) is mandatory to deploy direct borohydride fuel cell (DBFC) systems to power portable and mobile devices. Currently, DBFCs rely on noble metal electrocatalysts and are not capable of fully profiting from the high theoretical DBFC voltage due to the competing hydrogen evolution reaction. Here, highly efficient noble metal-free BOR electrocatalysts based on carbon-supported Ni nanoparticles considerably outperform Pt/C at overpotentials as low as 0.2 V, both in half-cell and in unit fuel cell configurations. Precise control of the oxidation state of surface Ni determines the electrocatalytic activity. Density functional theory (DFT) calculations ascribe the significant activity of Ni compared to Pt, Pd, or Au to a better balance in the adsorption energies of H_ad, OH_ad, and B-containing reactive intermediates. These findings suggest design principles for efficient noble metal-free BOR electrocatalysts for DBFCs.