Activating the Basal Plane of 2D Transition Metal Dichalcogenides via High-Entropy Alloying

TL;DR

This paper demonstrates that high-entropy alloying can activate the inert basal plane of 2D transition metal dichalcogenides, creating abundant catalytic sites and enabling the design of efficient, non-precious hydrogen evolution catalysts.

Contribution

It introduces high-entropy alloying as a method to stabilize and activate the basal plane of 2D TMDCs for catalysis, a novel approach in catalyst design.

Findings

High-entropy alloying stabilizes the 2H and 1T phases of TMDCs.

Alloy composition controls the phase stability and catalytic activity.

Predicted new non-precious HER catalysts based on alloy compositions.

Abstract

Two-dimensional (2D) materials, such as transition metal dichalcogenides (TMDCs) in the 2H or 1T crystal phases, are promising (electro)catalyst candidates due to their high surface to volume ratio and composition of low-cost, abundant elements. While the edges of elemental TMDC nanoparticles, such as MoS$_2$, can show significant catalytic activity, the basal plane of the pristine materials are notoriously inert, which limits their normalized activity. Here we show that high densities of catalytically active sites can be formed on the TMDC basal plane by alloying elements that prefer the 2H (1T) phase into a 1T (2H) structure. The global stability of the alloy, in particular whether it crystallizes in the 2H or 1T phase, can be controlled by ensuring a majority of elements preferring the target phase. We further show that the mixing entropy plays a decisive role for stabilizing the alloy implying that high-entropy alloying becomes essential. Our calculations point to a number of interesting non-precious hydrogen evolution catalysts, including (CrHfTaVZr)S$_2$ and (CrNbTiVZr)S$_2$ in the T-phase and (MoNbTaVTi)S$_2$ in the H-phase. Our work opens new directions for designing catalytic sites via high-entropy alloy stabilization of locally unstable structures.