Amorphous CoO_<i>x</i>-Decorated Crystalline RuO₂ Nanosheets as Bifunctional Catalysts for Boosting Overall Water Splitting at Large Current Density

Abstract

Developing efficient bifunctional water electrolysis catalysts applied at large current density is desirable. Herein, an amorphous CoOx-decorated crystalline RuO2 nanosheet catalyst self-supported on nickel foam (CoOx–RuO2/NF) with high performance for both oxygen and hydrogen evolution reaction (OER and HER) is prepared successfully by hydrothermal method and annealing. The overpotentials at ±1500 mA cm–2 for OER and HER are 420 and 215 mV, respectively, in 1.0 M KOH solution. Remarkably, it shows good durability with small decline in performance after 48 h durability test for OER and HER at ±1500 mA cm–2. Furthermore, it only needs 1.49 V to reach 10 mA cm–2 for overall water splitting (OWS); the decline of activity is satisfactory after 48 h durability test at 1500 mA cm–2. The reason could be because of the sufficient active sites generated by the crystalline–amorphous combination and self-supporting nanosheet structure. This work therefore proposes an effective strategy for preparing a high-performance OWS catalyst, especially at large current density.