Controlled Synthesis of CuCo2 S4 @Ni(OH)2 Hybrid Nanorod Arrays for Water Splitting at an Ultralow Cell Voltage of 1.47 V.

Developing environmentally friendly and highly active water splitting catalysts would be of great significance for clean energy conversion and utilization processes. Heterogeneous CuCo2 S4 @Ni(OH)2 nanorod arrays with abundant oxygen vacancy firstly have been designed through a controllable hydrothermal and electrodeposition method. The synergies and open structures of the particular hierarchical structure together with the abundant oxygen vacancies offer more surface reactive centers, which can promote the electron transfer rate and reduce the activation energy of intermediate species. The CuCo2 S4 @Ni(OH)2 -20 min nanorod arrays are considered as an excellent and robust electrocatalyst for the proton reduction under an alkaline condition with an extraordinary low overpotential of 117 mV at 10 mA cm-2 . The CuCo2 S4 @Ni(OH)2 -20 min heterostructures electrode is also stable and robust for the water oxidation reaction, needing an overpotential of only 250 mV to obtain 100 mA cm-2 . Therefore, an alkaline electrolyzer was designed using CuCo2 S4 @Ni(OH)2 -20 min nanorod arrays as bifunctional electrocatalyst, which can complete overall water splitting at a cell voltage of 1.47 V with 10 mA cm-2 , suggesting a promising combination of the same material for efficient overall water splitting device. The cell voltage of 1.47 V, to our knowledge, is among the lowest values of the published support catalysts for electrocatalytic water splitting up to now.