Synthesis of ruthenium oxide nanosheets with fourth-period elements for alkaline oxygen evolution reaction

A comprehensive series of Ru-based bimetallic oxide nanosheets with fourth-period elements (M = Cr, Mn, Fe, Co, Ni, Cu, Zn, and Ga) was synthesized via a unified puffing-template combustion method and systematically evaluated for the alkaline oxygen evolution reaction (OER). As revealed by X-ray diffraction, among the examined metals, Cr and Ga exclusively induced chemically selective solid-solution formation within the rutile RuO₂ lattice, a structural prerequisite for modulating the electronic structure of the active Ru sites and enhancing the OER activity. The OER activity of the optimal compositions Ru_0.38Ga_0.62Ox and Ru_0.71Cr_0.29O_x surpassed that of pristine RuO_x. However, a 50 h chronopotentiometric study revealed a decisive shift in the activity-stability relationship, with Ru_0.71Cr_0.29O_x maintaining a nearly constant operating potential, whereas Ru_0.38Ga_0.62O_x rapidly deactivated due to Ga³⁺ leaching. X-ray photoelectron spectroscopy and electron microscopy confirmed that Cr³⁺ acts as a valence-pinning agent, suppressing Ru oxidation, thereby reducing the density of oxygen vacancies and number of stable covalent Ru-O bonds. The results demonstrate that Ru_0.72Cr_0.29O_x is a promising and durable anode for the alkaline OER and highlight the importance of durability testing in concurrence with overpotential benchmarking.