Construction of Ni³⁺-rich, Ru-doped NiO nanoparticles with lattice strain for enhanced OER performance

Manipulating the intrinsic activity of heterogeneous catalysts at the atomic level is an effective strategy to improve their electrocatalytic performances but remains a great challenge. Herein, we synthesized Ni³⁺-rich, Ru-doped NiO nanoparticles (Ru-NiO) through a two-step thermal treatment method. As an OER catalyst, the obtained Ru-NiO exhibited a low overpotential of 220 mV at a current density of 10 mA cm^-2 and a Tafel slope of 78 mV dec^-1 in alkaline media, outperforming NiO-based electrocatalysts prepared via the conventional sol-gel synthesis method and conventional calcination synthesis method. Employing this strategy, the introduction of trace amounts of Ru atoms in the NiO lattice, leading to lattice strain and electron redistribution, results in superior OER activity. Our results further illustrate that the Ru-O-Ni bonds in the precursor play a vital role in this strategy for the formation of Ru-NiO nanoparticles with lattice strain. At the same time, density functional theory (DFT) results further confirmed that the Ru-NiO nanoparticles have a low d-band center caused by the lattice strain effect to improve the adsorption energy of oxygen-containing intermediates, ultimately accelerating OER kinetics. Thus, this work provides a new pathway for the design of NiO-based OER catalysts.