Modulating the electronic structure of NiFe layered double hydroxide via anion engineering for enhanced oxygen evolution.

Alkaline water electrolysis is emerging as a promising technology for large-scale hydrogen production. However, NiFe layered double hydroxide (NiFe LDH), one of the leading-edge oxygen evolution reaction (OER) electrocatalysts in alkaline water electrolysis, still faces challenges in effectively modulating highly active species to enhance its advanced performance, which is crucial for promoting industrial development. Herein, we report a facile anion engineering strategy to construct a novel NiFe LDH as an efficient anode electrocatalyst. Induced by sulfate, electrons could be withdrawn from the metal centers, elevating the oxidation state of Ni and Fe species in the metal hydroxide layers, which act as the prominent active sites. The modified structure with a narrowed pseudogap enhances charge transport and optimizes intermediate adsorption energy, delivering a low overpotential of 223 mV and surpassing the commercial benchmark in a two-electrode water-splitting electrolyzer. Moreover, it delivers excellent stability, maintaining over 70 h at a current density of 100 mA cm in alkaline OER, and also demonstrates high stability in seawater electrolysis, benefitting from the synergistic effects of carbonate and sulfate anions. This work provides a promising avenue for the rational design of advanced OER catalysts for water electrolysis.