Directing in-situ self-optimization of single-atom catalysts for improved oxygen evolution

The demand for clean and sustainable energy has encouraged the production of hydrogen from water electrolyzers. To overcome the obstacle to improving the efficiency of water electrolyzers, it is highly desired to fabricate active electrocatalysts for the sluggish oxygen evolution process. However, there is generally an intrinsic gap between the as-prepared and real electrocatalysts due to structure evolution under the oxidative reaction conditions. Here, we combine in-situ anionic leaching and atomic deposition to realize single-atom catalysts with self-optimized structures. The introduced F ions facilitate structural transformation from Co(OH)xF into CoOOH(F), which generates an amorphous edge surface to provide more anchoring sites for Ir single atoms. Meanwhile, the in-situ anionic leaching of F ions elevates the Co valence state of Ir1/CoOOH(F) more significantly than the counterpart without F ions (Ir1/CoOOH), leading to stronger adsorption of oxygenated intermediates. As revealed by electrochemical measurements, the increased Ir loading together with the favored adsorption of *OH intermediates improve the catalytic activity of Ir1/CoOOH(F). Specifically, Ir1/CoOOH(F) delivered a current density of 10 mA cm−2 at an overpotential of 238 mV, being lower than 314 mV for Ir1/CoOOH. The results demonstrated the facility of the in-situ optimization process to optimize catalyst structure for improved performance.