Ruthenium oxychloride supported by manganese oxide for stable oxygen evolution in acidic media

Abstract

Despite the recent advances in enhancing the durability and reducing the overpotential of ruthenium (Ru)-based electrocatalysts for acidic oxygen evolution reaction (OER), their stability hardly meets the requirement of practical application. Moreover, a cost-effective strategy to stabilize the highly active but unstable Ru species is desirable. Herein, we report a stable electrocatalyst for acidic OER by dispersing the Ru oxychloride active species into a manganese oxide support (RuOCl@MnO_x) to form highly dispersed Ru–O–Mn without the alteration of vibrational modes and bond parameters of the MnO₆ group, as suggested by Raman and synchrotron radiation characterization studies. The catalyst is stable for continuous operation over 280 h with an overpotential of 228 mV at 10 mA cm⁻² and over 200 h at 100 mA cm⁻², among the most stable low-mass-loading Ru-based OER electrocatalysts in acidic media. Complementary theoretical calculations ascribe the excellent stability to its high oxidation potential and low formation/surface energies, consistent with experimental observations. The enhanced activity is attributed to the four-coordinated Ru site that bears a low overpotential determined by the formation of O* from OH*. Our work thus offers a new strategy for synthesizing robust OER electrocatalysts of PEM electrolyzers with superior activity.