Theoretical and experimental study on the effect of mechanical strain force activated polyhedron on oxygen evolution reaction performance and mechanism

Abstract

Developing cost-effective and high-performance electrocatalysts is crucial for overcoming the slow oxygen evolution reaction (OER) observed in the process of water splitting. Herein, an exquisite iron-cobalt bimetallic sulfide featuring exposing more crystal faces and stronger crystallinity is manipulated via a mechanical stress strategy, which may offer additional active sites for the OER process. Particularly, the prepared Fe_0.5Co_0.5/SNC exhibits notable OER activity, characterized by a low overpotential of 310 mV at a current density of 10 mA cm⁻² and a high current density of 131 mA/cm² at a voltage of 1.8 V (versus RHE). Additionally, post-stability tests analysis on the material revealed a reversible oscillation of iron and cobalt valence states between 2⁺ and 3⁺, indicating the material's sensitivity to reactive oxygen species, which enhances its OER catalytic performance. The continuous adsorption and desorption of reaction intermediates with the material's matrix perpetually trigger the activation, maintaining the catalytic activity. Theoretical calculations suggest that orbital hybridization among iron, cobalt, and sulfur, along with an appropriate d-band center, enhance the electron exchange rate, facilitating the adsorption and dissociation of intermediates on the material, thereby promoting the OER process. Our findings provide new insights for the design and production of efficient, cost-effective OER electrocatalysts, contributing to the industrialization of OER catalysts.