Tailoring the Electronic and Hydrophilic Properties of Nickel Oxide Hydroxides by Bismuth Incorporation Toward Enhanced Alkaline Electrocatalytic Water Oxidation

Identification of electrocatalysts with suitable electronic and hydrophilic properties is indispensable for boosting the alkaline oxygen evolution reaction (OER). The incorporation of bismuth (Bi) into Nickel oxide hydroxides is presented to simultaneously tune these properties of the catalyst toward enhanced OER. It is shown that the Bi doping endows more reversibility of Ni, enhances the lattice oxygen reactivity, and leads to a weakly binding surface for the resultant NiBi(OH)_x electrocatalyst. These can not only accelerate the redox transformation of OER intermediates but also enhance surface oxygen-involved OER process, which collaboratively boost the OER kinetics. Moreover, the Bi incorporation manipulates the hydrophilic property of the electrode, which facilitates mass transfer by allowing more facile diffusion of gaseous products and electrolytes. As a result, the optimized Ni₉₇Bi₃(OH)_x electrode delivers a current density of 500 mA cm^-2 at an overpotential of 357 mV without losing performance for over 1000 h, on par with the state-of-the-art NiFe anodes. This work provides an effective strategy to enhance the electrocatalytic performance in OER through the integration of electronic regulation and hydrophilic modification.