pH-dependent mechanism of oxygen evolution in highly disordered RuO2 nanosheets.

Amorphous materials have garnered significant research interest because of their high structural tolerances and useful functionalities. Here, we develop an effective synthesis method for atomically thin, highly disordered RuO2 nanosheets that exhibit a promising electrocatalytic performance and a distinct pH-dependent operation mechanism. The poor orbital overlap and coordinatively unsaturated nature of the Ru ions in the highly disordered RuO2 nanosheets have a synergistic effect on the electrocatalytic performance by enhancing surface adsorption and the activation of lattice oxygen. The highly disordered RuO2 nanosheets exhibit high electrocatalytic activities in the oxygen evolution reactions (OERs) performed in both alkaline and acidic electrolytes. Various in situ spectroscopic investigations reveal that structural disordering causes a greater contribution of the lattice oxygen participation mechanism in acidic media than in alkaline media. This pH-dependent mechanism can be attributed to the amorphization-induced enhancement of lattice oxygen occupation in the acidic OER medium and increased hydroxide adsorption in the alkaline OER medium. Such disorder-driven pH tuning of the electrocatalytic operation mechanism enables the fabrication of pH-universal high-performance electrocatalysts.