Electrocatalytic Study for Hydrogen Evolution Reaction on MoS$_2$/BP and MoSSe/BP in Acidic Media

TL;DR

This study uses first-principles calculations to explore the hydrogen evolution reaction on MoS2/BP and MoSSe/BP heterostructures, revealing their potential as efficient, earth-abundant electrocatalysts in acidic media.

Contribution

It introduces a detailed theoretical analysis of MoS2/BP and MoSSe/BP heterostructures for HER, highlighting their low reaction barriers and conditions favoring efficient hydrogen production.

Findings

MoSSe/BP shows feasible HER with no barrier at low coverage.

High coverage and low proton concentration favor HER via Heyrovsky reaction.

No significant difference between MoS2/BP and MoSSe/BP in high coverage conditions.

Abstract

Molecular hydrogen (H$_2$) production by electrochemical hydrogen evolution reaction (HER) is being actively explored for non-precious-metal based electrocatalysts that are earth-abundant and low cost like MoS$_2$. Although it is acid-stable, its applicability is limited by catalytically inactive basal plane, poor electrical transport and inefficient charge transfer at the interface. Therefore, the present work examines its bilayer van der Waals heterostructure (vdW HTS). The second constituent monolayer Boron Phosphide (BP) is advantageous as an electrode material owing to its chemical stability in both oxygen and water environments. Here, we have performed first-principles based calculations under the framework of density functional theory (DFT) for HER in an electrochemical double layer model with the BP monolayer, MoS$_2$/BP and MoSSe/BP vdW HTSs. The climbing image nudged elastic band method (CI-NEB) has been employed to determine the minimum energy pathways for Tafel and Heyrovsky reactions. The calculations yield that Tafel reaction shows no reaction barrier. Thereafter, for Heyrovsky reaction, we have obtained low reaction barrier in the vdW HTSs as compared to that in the BP monolayer. Subsequently, we have observed no significant difference in the reaction profile of MoS$_2$/BP and MoSSe/BP vdW HTSs in case of high coverage (25 %) and 1/3 H$^+$ concentration (conc.). However, in the case of small coverage (11 %) and 1/3 H$^+$ conc., MoSSe/BP shows feasible Heyrovsky reaction with no reaction barrier. Finally, on comparing the coverages with 1/4 H$^+$ conc., we deduce high coverage with low conc. and low coverage with high conc. to be apt for HER via Heyrovsky reaction path.