Ruthenium composited NiCo2O4 spinel nanocones with oxygen vacancies as a high-efficient bifunctional catalyst for overall water splitting

Electrocatalytic water splitting is a critical technique for generating clean hydrogen energy, where the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are involved. Generally, the OER process (bottleneck step) occurs more favorably in alkaline solution, while the HER process in acidic solution. Structure or composition design of electrocatalyst are effective strategies to achieve high performances for both OER and HER in alkaline environment toward overall water splitting. Herein, we report a unique electrocatalyst composed of RuO2 nanoparticles on NiCo2O4 nanocones ([email protected]2-NCs) hybrid structure via the hydrothermal coprecipitation and subsequent calcination. The [email protected]2-NCs show higher oxygen vacancy density than that of NiCo2O4@RuO2 nanosheets ([email protected]2-NSs). Employing the [email protected]2-NCs material as a bifunctional catalyst, a low cell voltage of 1.5 V is capable of overall water splitting with excellent stability of sustaining more than 42 h at 10 mA cm−2 in 1 M KOH electrolyte, which is superior to 2.0 V of [email protected]2-NSs as well as 1.6 V of commercial Pt/C-RuO2 couple. The current work may provide a scalable and cost-efficient approach for developing advanced nanocomposite catalysts for water splitting.