Mo2se3 and Mo3se2 Monolayers as Efficient Electrocatalysts for Water Splitting

Abstract

Developing efficient, low-cost catalysts is paramount for advancing hydrogen production through water electrolysis. In this study, we explore the electrocatalytic potential of novel 2D monolayers, Mo2X3 and Mo3X2 (X = S, Se), using first-principles calculations. At the electronic structure level, the formation of robust polar covalent bonds through Mo d-orbital and X p-orbital hybridization ensures both structural integrity and intrinsic metallic characteristics, resulting in superior electrical conductivity. Catalytically, the monolayers Mo3S2, Mo2Se3, and Mo3Se2 demonstrate HER performance on par with Pt, driven by charge transfer induced enhancement of X atom activity. Particularly noteworthy is the Janus structure of Mo2Se3, which exposes a higher density of active sites, significantly amplifying its catalytic efficiency. The volcanic curve indicates that molybdenum selenide shows better catalytic performance than molybdenum sulfide. These monolayers facilitate spontaneous hydrogen generation via the Volmer-Heyrovsky pathway, underscoring their suitability as efficient electrocatalysts. Combining high specific surface area, excellent charge transport properties, and unique catalytic mechanisms, Mo2Se3 and Mo3Se2 monolayers emerge as highly compelling materials for water electrolysis. This study not only advances the application of 2D materials in energy conversion but also provides a strategic framework for designing next-generation electrocatalysts that are both high-performing and cost-effective.

Keywords: electrocatalysis, hydrogen evolution mechanism, DFT