Elemental Engineering of High-Charge-Density Boron in Nickel as Multifunctional Electrocatalysts for Hydrogen Oxidation and Water Splitting

The development of efficient and earth-abundant multifunctional electrocatalysts is challenging yet critical for clean energy systems. Herein, we present the development of a heteroatom B-doping approach, namely, B-doped Ni (B-Ni), for multifunctional electrocatalysis. The B-Ni catalysts exhibited multifunctional activities in an alkaline solution, including the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and hydrogen oxidation reaction (HOR). The B-Ni catalysts, as both the cathode and the anode, showed outstanding water splitting performance with cell voltages of 1.62 and 1.74 V versus reversible hydrogen electrode (RHE) to achieve 10 and 100 mA cm^–2, respectively. Furthermore, the B-Ni catalysts produced an HOR current density of 0.85 mA cm^–2 at 0.1 V versus RHE. Density functional theory (DFT) calculations showed that the doped B atom can extract electrons from its adjacent Ni site, resulting in increased charge densities on the B site and a loss of charge densities on the surrounding Ni atoms. Such charge redistribution is favorable to the HOR and HER processes. The heteroatom-doping approach of the B-Ni catalyst provides an alternative strategy for the development of earth-abundant electrocatalysts in both energy storage and conversion.