Bifunctional Noble Metal-Free Ternary Chalcogenide Electrocatalysts for Overall Water Splitting

Hydrogen has been identified as a clean, zero-carbon, sustainable, and promising energy source for the future, and electrochemical water splitting for hydrogen production is an emission-free and efficient energy conversion technology. A major limitation of this approach is the unavailability of efficient, abundant, and inexpensive catalysts, which prompts the need for new catalytic materials. Here, we report the synthesis and electrocatalytic properties of a novel transition-metal-based ternary chalcogenide family, LaMS 3 (M = Mn, Fe, Co, and Ni). These materials exhibit bifunctional catalytic activity toward the two half-reactions of the water-splitting process, with LaNiS 3 being the most active material for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). The LaMS 3 compounds show long-term stability with negligible change in the overpotential at a constant current density of 10 mA cm –2 over 18 h of measurements. As compared to the corresponding ternary oxides, the LaMS 3 materials exhibit higher activity and significantly lower Tafel slopes. These materials demonstrate overpotentials comparable to those of commercial catalysts at a current density of 300 mA cm –2 . The ability to catalyze both half-reactions of water electrolysis makes these materials promising candidates for bifunctional catalysts and presents a new avenue to search for high-efficiency electrocatalysts for water splitting.