Interfacial Engineering of MgCo2O4@Ni(OH)2 Heterostructures for Efficient Alkaline Water Oxidation

Abstract

Developing highly active, durable, and earth-abundant electrocatalysts is essential for advancing sustainable hydrogen production through electrochemical water oxidation. Herein, a hierarchical MgCo2O4@Ni(OH)2 heterostructure was constructed by electrodepositing Ni(OH)2 nanosheets onto MgCo2O4 nanorods and investigated as an electrocatalyst for alkaline water splitting. The intimate contact between the MgCo2O4 nanorod and Ni(OH)2 nanosheet creates a hierarchical architecture with abundant accessible surface sites and favorable pathways for electrolyte penetration and charge transport. Among the prepared electrodes, MCO@Ni(OH)2-2 exhibited the best OER performance, requiring an overpotential of 348 mV to achieve 10 mA cm−2 with a Tafel slope of 70.2 mV dec−1. The optimized electrode also showed a low charge-transfer resistance of 2.7 Ω, indicating favorable interfacial charge transport. Its hierarchical architecture provides a highly accessible electrochemical surface, shortened ion-diffusion pathways, and efficient electrolyte penetration, thereby promoting the adsorption and transformation of reaction intermediates. The enhanced performance is attributed to the optimized Ni(OH)2 nanosheet coverage, increased electrochemically active surface area, and synergistic interaction between the MgCo2O4 nanorod and Ni(OH)2. Furthermore, the electrode retained substantial electrocatalytic activity during prolonged cycling and continuous operation under alkaline conditions. These results demonstrate that engineering hierarchical oxide/hydroxide interfaces offers an effective approach for developing efficient transition-metal-based electrocatalysts for sustainable water splitting.