Alternate to Molybdenum Disulfide: A 2D, Few-Layer Transition-Metal Thiophosphate and Its Hydrogen Evolution Reaction Activity over a Wide pH Range

A two-dimensional, few-layer nickel thiophosphate, NiPS3, was introduced as a hydrogen evolution reaction catalyst from aqueous acidic, alkaline, and neutral solutions. NiPS3 is semiconducting in nature, and its band structure calculations revealed the importance of the [P2S6](4-) units in the adsorption of hydrogen and subsequent evolution. Onset potentials of -0.062, -0.065, and -0.298V versus RHE were observed in acidic, alkaline, and neutral media. Tafel slopes of 55, 48, and 94mVdec(-1) and exchange current densities of 1.8x10(-4), 6.1x10(-4), and 3.2x10(-5)Acm(-2) were observed in aqueous 0.5m H2SO4, 1m KOH, and 3.5% NaCl solutions, respectively. The catalyst was found to be very stable, and the constituting elements are earth abundant. The present study opens up a new class of semiconducting layered materials to catalyze various redox reactions. Achieving a single layer will be of great interest to electrical and magnetic devices.