Controlled Synthesis of a Three-Segment Heterostructure for High-Performance Overall Water Splitting.

Developing earth-abundant, highly active, and robust electrocatalysts capable of both oxygen and hydrogen evolution reactions is crucial for the commercial success of renewable energy technologies. Here we demonstrate a facile and universal strategy for fabricating transition metal (TM) sulfides by controlling the atomic ratio of TM precursors for water splitting in basic media. Density functional theory calculations reveal that the incorporation of Fe/Co can significantly improve the catalytic performance. The optimal material exhibits extremely small overpotentials of 208 mV for oxygen evolution and 68 mV for hydrogen evolution at 10 mA cm-2 with robust long-term stability. The optimized material was used as bifunctional electrodes for overall water splitting, which delivers 10 mA cm-2 at a very low cell voltage of 1.44 V with robust stability over 80 h at 100 mA cm-2 without degradation, much better than the combination of Pt and RuO2 as benchmark catalysts. The excellent water-splitting performance sheds light on the promising potential of such sulfides as high activity and robust stable electrodes.