Self-supported electrode of NiCo-LDH/NiCo₂S₄/CC with enhanced performance for oxygen evolution reaction and hydrogen evolution reaction

The exploitation of bifunctional electrocatalysts for stable and efficient water splitting is of great significant for the development of clean energy industry. Herein, a hierarchical NiCo-LDH/NiCo₂S₄/CC electrode is prepared on carbon cloth by coupling NiCo-LDH nanosheets with NiCo₂S₄ nanoneedles through a simple process. This NiCo-LDH/NiCo₂S₄/CC electrode serves as an efficient bifunctional electrocatalyst for overall water splitting with excellent activity and stability in alkaline media. The enhanced electrocatalytic performance is ascribed to the hierarchical structure, the synergistic effect of NiCo-LDH and NiCo₂S₄ as well as the phase transformation of NiCo₂S₄ in alkaline condition. The NiCo-LDH/NiCo₂S₄/CC electrode requires overpotentials of 254 and 219 mV to deliver the current density of 50 mA cm^-2 for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in 1 M KOH aqueous solution, respectively. The Tafel results further reveal favorable reaction kinetics during electrolysis. When used as the bifunctional electrode for overall water splitting, the NiCo-LDH/NiCo₂S₄/CC performs superior activity with a voltage of 1.64 V at the current density of 50 mA cm^-2. This work offers a new approach for the exploitation of high-performance and cost-efficient bifunctional catalysts for water splitting.