Synergistic Modulation of Active Sites and Charge Transport: N/S Co-doped C Encapsulated NiCo₂O₄/NiO Hollow Microrods for Boosting Oxygen Evolution Catalysis

Developing high-efficiency and cost-effective electrocatalysts for the oxygen evolution reaction (OER) is crucial for various energy conversion systems. Herein, N/S co-doped C encapsulated hollow NiCo₂O₄/NiO hexagonal rods (HNHR@N/S-C) as the electrocatalysts for OER have been successfully prepared with rational control of structure and composition. Experimental and theoretical results have highlighted that the NiCo₂O₄/NiO heterojunction in the obtained electrocatalyst can provide abundant active Ni and Co sites for the OER, leading to the highly enhanced OER performance. Moreover, attributed to the hierarchical hollow structure, which can provide a large surface area, and the improved electric conductivity with a coating of the N/S co-doped carbon layer, which can facilitate charge transport during the catalytic processes, a remarkable OER activity over HNHR@N/S-C with a low overpotential (η) of 285 mV (at j = 10 mA cm^–2) and a Tafel slope of 53.0 mV decade^–1 has been achieved, which is comparable to that of the noble metal catalyst IrO₂. Because of the protection of the N/S doped C layer coating, HNHR@N/S-C can also maintain the current density of 10 mA cm^–2 for at least 12 h in alkaline media without obvious losses of activity.