Modulation of chalcogen-functionalized MXenes Ti₂CT₂ (T?=?O, S, Se, and Te) as catalysts for hydrogen evolution reaction

Exploration and exploitation of efficient and nonprecious catalysts for hydrogen evolution reaction (HER) is one of the key solutions to energy problems. Two-dimensional (2D) MXenes have attracted extensive attention as potential catalysts and supports due to their unique structure and customizable properties. In this work, we have systematically investigated the structural stability and electronic properties of chalcogen-functionalized MXenes Ti2CT2 (T = O, S, Se, and Te) and Pt-anchored Ti2CT2 MXenes (Pt-Ti2CT2). Density functional theory calculations have discovered that all Ti2CT2 exhibit metallic electronic structures except Ti2CO2 with an indirect bandgap. Additionally, the electronic densities of states at Fermi level for Pt-Ti2CT2 are greatly enhanced after anchoring Pt atoms. The reduction of chalcogen electronegativity is recognized to mainly contribute to weaker bond strength but greater electronic activity. Moreover, Pt-Ti2CTe2 is predicted to exhibit near-zero Gibbs free energy of hydrogen adsorption especially at high hydrogen coverage, indicating its significant potential as HER catalysts. It is also revealed that Ti2CT2 and Pt-Ti2CT2 MXenes are not only ideal candidates of catalyst materials but also could serve as good catalyst substrates. This work provides insights into the structural and chemical complexity of MXenes for catalyst applications but also demonstrates a new strategy to modulate high-efficiency and low-cost catalyst and support materials.