In situ formation of robust nanostructured cobalt oxyhydroxide/cobalt oxide oxygen evolution reaction electrocatalysts

Abstract

The design of efficient and stable oxygen evolution reaction (OER) catalyst-based earth-abundant metal precursors is crucial for large-scale energy conversion and storage. To-date, many catalyst materials are limited by poor stability in harsh oxidative conditions. Thus, much research is targeted at developing materials that can operate under demanding OER conditions. One promising approach is the in situ formation of catalysts which are inherently stable under the oxidizing, alkaline conditions often used in OER studies. Here, we report how mixed metal sulfide precursors (i.e. CoMo₂S₄ and FeS₂) which give the low overpotentials (307 mV at j = 10 mA cm⁻²) at the beginning of catalysis, are converted in situ to give a highly stable composite OER catalyst under alkaline OER conditions (1 M aqueous KOH solution, pH = 13.8). Mechanistic studies reveal that under operation, the precursor materials are converted to γ-CoOOH nanofibers and Co₂O₃ nanoparticles, both well-known prototype OER catalysts. The report demonstrates that the presence of crystalline mix metal sulfide precursors is critical for the simultaneous in situ formation of the active catalysts, highlighting that use of these earth-abundant minerals might offer an economically and chemically viable route for scalable catalyst development.