Heteroanion induced structural asymmetricity centered on Ru sites switches the rate-determining step of acid water oxidation

The exploration of Ir-free-based oxygen evolution reaction (OER) catalysts is the key for electrolytic hydrogen production. Herein, a Se, S heteroanion modulation strategy is proposed to improve the OER activity and stability of cationic Ru sites through induced structural asymmetricity. Due to the differences between the intervening Se and S in atomic radius, metallicity and ionization energy, they not only alter the octahedral arrangement and bond length of the pristine RuS2, but also act as a charge modulator to promote electron accumulation toward Ru. Impressively, the electronic structure and coordination environment optimized Ru2(S3Se) achieves hyper water oxidation activity (186 mV@10 mA cm-2), 28.2 and 10.5 times that of commercial RuO2 in mass and specific activities, respectively. Moreover, the synergistic effect of Se and S effectively inhibits the formation of soluble Ru species, thereby upgrading the OER stability. Theoretical calculations and in situ detection technology further unveil the reaction path and structure changes on Ru2(S3Se) surfaces, rationalizing the enhanced performance by decreased energy barriers of the rate-determining step (RDS) and strong coupling of Se-Ru-S bonds. The intervening Se induces the structural asymmetricity of Ru-S6 octahedrons and then regulates the electronic structure of the active Ru site, which possesses excellent acid water oxidation performance as an Ir-free catalyst.