Ni³⁺-enriched nickel-based electrocatalysts for superior electrocatalytic water oxidation

A good understanding of the strategy to improve the reconstruction process and catalytic mechanism of non-noble transition metal electrocatalysts in the oxygen evolution reaction (OER) is crucial to achieving high-efficiency and energy-saving hydrogen production because it is considered the rate-determining step in water splitting. In this work, Fe-doped NiO nanosheet arrays are prepared on carbon cloth (Fe/NiO/CC) by a simple solution method and subsequent sonication. The Fe dopants facilitate energy-efficient and rapid surface reconstruction, activate more Ni³⁺ species, and generate more oxygen vacancies to enable fast and efficient OER. As a result, an overpotential of merely 288 mV is required for a current density of 100 mA cm⁻² by the Fe/NiO/CC electrocatalyst and a small Tafel slope of 72.6 mV dec⁻¹ is observed in the alkaline electrolyte. Based on density-functional theory calculation, the difference in the bonding and charge redistribution in NiO caused by Fe dopants modulates the electronic structure and coordination unequally, consequently increasing the number of active sites and enhancing the intrinsic catalytic activity as well. The results provide a deeper understanding of how heteroatom doping modulates the intrinsic activity of active atoms in transition metal-based electrocatalysts and reveal the role in reconstruction in electrocatalytic OER.