Ruthenium-nickel oxide derived from Ru-coupled Ni metal-organic framework for effective oxygen evolution reaction

Developing Ru-based catalysts with both high activity and stability for the oxygen evolution reaction (OER) is very significant in the water electrolysis technique. Here, a bimetallic metal oxide catalyst (RuO₂-NiO) derived from Ru-coupled Ni metal-organic framework (Ni-MOF) by using terephthalic acid as the ligand was successfully synthesized through a facile ultrasonic treatment and subsequent thermal annealing approach; and the effective role of the coupled effect between RuO₂ and NiO in stabilizing Ru was found significant in OER catalysis. A relatively small d-band center due to the electronic structure regulation and synergistic effect of the heterostructure was found to cause weakened adsorption of surface oxygen species. Theoretical calculations demonstrated that the electronic modulation between RuO₂ and NiO can significantly accelerate the dissociation of water and modulate the chemical adsorption of oxygen intermediates on the catalyst, thereby enhancing the OER activity of the catalyst. The optimized catalyst of RuO₂-NiO afforded a current density of 10 mA cm^-2 at low overpotentials of 210 mV toward OER, and good catalytic stability, kinetics and efficiency were also discussed. This remarkable catalytic performance can be attributed to the unique sheet-like structure and porous morphology of the catalyst with increased exposure of active sites and the coupling effect between RuO₂ and NiO for moderate binding strength to the intermediates. This study showed an effective approach for bimetallic oxide catalyst fabrication and their applications in energy conversion reactions.