Accelerated oxygen evolution enabled by encapsulating hybrid CoOx/RuO2 nanoparticle with nanoporous carbon

Abstract

The anodic oxygen evolution reaction (OER) is a four-electron reaction process with the relatively sluggish kinetics, which has become one of the main factors limiting the efficiency of the hydrogen evolution reaction in water splitting, so it is crucial to improve the kinetics of OER. Herein, a new RuO2-based composite catalyst Co-Ru-Py@500 has been designed with abundant pore spaces formed by the stacking of nanoparticles, where the nanoparticle comprises CoOx/RuO2 hybrid species and an encased carbon layer involving holey space. The Co-Ru-Py@500 possesses a relatively large specific surface area and a higher proportion of hydroxyl species than Ru-Py@500 without the introduction of CoOx species. The catalyst Co-Ru-Py@500 shows a smaller onset potential of 1.39 V vs. RHE and overpotential (230 mV@10 mA cm−2) than Ru-Py@500, and significantly favorable tafel slope, electrochemical impedance. In addition, the Fe-Ru-Py@500 and Ni-Ru-Py@500 introduced with FeOx or NiOx species are still inferior to Co-Ru-Py@500, but both of them show a better OER activity than Ru-Py@500. Through introducing Co, Fe, and Ni oxidation state species, the catalytic activity of RuO2 can be promoted to varying degrees. The design strategy in this work provides a significant guidance for the rational design of efficient OER catalysts.