A universal approach: Nanodiamond mediated reduction of Co nanoparticle exsolution from La0.7Sr0.2Fe0.8Co0.2O3 for enhanced oxygen evolution reaction

Abstract

The in situ exsolution process for metallic Co is crucial for developing low-cost and efficient oxygen evolution reaction (OER) catalysts based on perovskite materials. However, traditional exsolution methods normally require working in a hydrogen-reducing atmosphere. To address these limitations, by introducing nanodiamond (ND) into La0.7Sr0.2Fe0.8Co0.2O3 (LSFC), Co nanoparticles (NPs) were exsolved on the surface after thermal treatment. Owing to the unique sp2/sp3 hybrid structure of ND, the electron transfer at high temperature enhances the electron density on the ND surface, creating a reducing environment for the exsolution of Co NPs. The electrocatalyst exhibits significantly reduced overpotentials (265 mV at 10 mA cm−2 and 327 mV at 100 mA cm−2), a small Tafel slope of 52.14 mV dec−1, and good stability (88.9% of initial current density after a chronoamperometric durability test). This enhancement primarily results from the exsolution of Co NPs, which increases the number of active sites. Density functional theory calculations explain the role of ND in improving OER performance. This approach holds great promise for innovating various energy storage and conversion technologies.