Transition Metal-based Ternary Chalcogenides as Electrocatalysts for 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, efficient energy conversion technology. A major limitation to this approach is the non-availability of efficient, abundant, inexpensive catalysts for water splitting. To address this issue, we explore late transition metal-based ternary sulfides, with the general formula LaMS₃ (M = Mn, Fe, Co, Ni) as electrocatalysts for hydrogen evolution reaction (HER), and oxygen evolution reaction (OER). In this work, we report synchrotron powder diffraction studies and extended x-ray absorption fine structure (EXAFS) analysis to elucidate the structure of these novel materials. Composition analysis using X-ray fluorescence spectroscopy (XRF) confirms the stoichiometric ratio of 1:1:3 for La, M, and S. These materials exhibit bifunctional catalytic activity, with overpotentials of 330-370 mV at a current density of 10 mA/cm² for both HER and OER. These materials also show long-term stability with a negligible change in the overpotential at a constant current density of 10 mA/cm² over 24 hours. The ability to catalyze both half-cell reactions of water electrolysis makes these materials promising candidates for bifunctional catalysts and calls for further work on these compounds to understand the catalytic mechanisms to improve their performance.