Free-standing Co/Zn sulfide supported on Cu-foam for efficient overall water splitting

High-performance bifunctional electrocatalysts for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are arousing great interest aiming at efficient electrochemical splitting of water. Herein, we report a facile strategy to fabricate Co/Zn sulfide supported on Cu-foam (CoZn-S/Cu-F) as a free-standing electrode with high-performance for overall water splitting. In half-cell electrochemical systems, the overpotentials required to reach the current densities of ±10 mA cm−2 for the OER and HER are only 170 and 130 mV, respectively. After a long-term stability test running 20 000 cyclic voltammograms, the respective potential losses for the OER and HER are only 82 and 41 mV at ±50 mA cm−2. The constructed overall water splitting system driven by simulated solar energy also exhibits prominent performance with gas bubbles continuously generated at both electrodes. A cell voltage of only 1.58 V is required to reach the current densities of ±10 mA cm−2, surpassing the commercialized noble metal and state-of-the-art non-noble metal electrodes. The excellent performance for the overall water splitting is ascribed to the CoS nanoparticles covered with ZnS nanoflocs on the highly conductive Cu-foam, which allows close interfacial contact with the electrolyte, promotes mass and charge transfer, and facilitates desorption of the generated gas from the catalyst surface.