Few-Layer Iron Selenophosphate, FePSe₃: Efficient Electrocatalyst toward Water Splitting and Oxygen Reduction Reactions

There has been a spurt of activity in using layered MPX3 (M = transition metal, X = chalcogen, S/Se/Te) compounds in various studies including catalysis and devices. In the present study, low band gap, ternary iron selenophosphate (FePSe3) is introduced as an excellent and highly stable trifunctional electrocatalyst for hydrogen evolution, oxygen evolution, and oxygen reduction reactions. It is observed that the present catalyst is useful in evolving hydrogen over a wide pH range including seawater environment. Density functional theory calculations reveal various parameters that help improve the electrocatalytic activity of the layered material. Covalency of the Fe–Se bond, distortion in the crystal structure, and adsorption properties are shown to be responsible for the observed high catalytic activity.