Hierarchical assembly of RuO2/MoOx/CoNi-LDH nanocomposite for enhanced performance in acidic overall water splitting

The development of electrocatalysts with bifunctionality in acidic media is crucial for advancing proton exchange membrane water electrolyzers to produce clean hydrogen fuel. Herein, an efficient bifunctional RuO 2 /MoO x /CoNi-LDH nanocomposite was synthesized for the first time via a coprecipitation and two-step hydrothermal method and used as an electrocatalyst for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), thereby contributing to efficient overall water splitting (OWS). When used as an electrocatalyst in 0.5 M H 2 SO 4 , the RuO 2 /MoO x /CoNi-LDH requires an overpotential of 185, 221, and 262 mV for OER and 33, 65, and 101 mV for HER to reach the current density of 20, 50, and 100 mA/cm 2 , respectively. The improved electrochemical performances of RuO 2 /MoO x /CoNi-LDH are well supported by a low charge transfer resistance, high electrochemical surface area, optimized nanocomposite structure, and the synergistic interaction among the RuO 2 NPs, MoO x nanosheet (NSs), and CoNi-LDH. Importantly, in acidic OWS, bifunctional RuO 2 /MoO x /CoNi-LDH exhibits excellent activities and merely requires a low voltage of 1.53 V to reach the current density of 20 mA/cm 2 , lower than most of the mixed-metal-based bifunctional electrocatalysts reported in acidic media. This study provides an efficient and cost-effective method for preparing high-performance mixed-metal nanocomposites for electrochemical water splitting in acidic environments and beyond.