Computational Study of the Curvature-Promoted Anchoring of Transition Metals for Water Splitting.

Weiwei Liu,Xiaoshuang Li,Youchao Kong,Pengfei Liu,Bo Wang,Tianwei He,Alain R Puente Santiago

doi:10.3390/nano11123173

Abstract

Generating clean and sustainable hydrogen from water splitting processes represent a practical alternative to solve the energy crisis. Ultrathin two-dimensional materials exhibit attractive properties as catalysts for hydrogen production owing to their large surface-to-volume ratios and effective chemisorption sites. However, the catalytically inactive surfaces of the transition metal dichalcogenides (TMD) possess merely small areas of active chemical sites on the edge, thus decreasing their possibilities for practical applications. Here, we propose a new class of out-of-plane deformed TMD (cTMD) monolayer to anchor transition metal atoms for the activation of the inert surface. The calculated adsorption energy of metals (e.g., Pt) on curved MoS2 (cMoS2) can be greatly decreased by 72% via adding external compressions, compared to the basal plane. The enlarged diffusion barrier energy indicates that cMoS2 with an enhanced fixation of metals could be a potential candidate as a single atom catalyst (SAC). We made a well-rounded assessment of the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), which are two key processes in water splitting. The optimized Gibbs free energy of 0.02 for HER and low overpotential of 0.40 V for OER can be achieved when the proper compression and supported metals are selected. Our computational results provide inspiration and guidance towards the experimental design of TMD-based SACs.

Highlights

Hydrogen gas is considered the most plausible alternative to solve the energy crisis due to its green products, high heat of combustion, and sustainable properties [1,2,3].Generally, electrolytic water is believed to be a clean and simple way to generate hydrogen compared with many other methods
We demonstrate that the large dissociation barrier of H2 O in alkaline solution resulted in a slow reaction rate of hydrogen evolution reaction (HER) of the M@curved MoS2 (cMoS2) in alkaline environment
Our previous study indicated that the curved MoS could promote the surface activation due to the low adsorption energy of H atoms, but the optimized Gibbs free energy of 1.25 eV is still high for practical applications [32]

Summary

Introduction

Electrolytic water is believed to be a clean and simple way to generate hydrogen compared with many other methods. The selection of traditional catalysts focuses on noble metals (like bulk Pt), for their high stability, chemical activity and selectivity, and even inter-atomic cooperation [4,5,6]. The low rate of exposed active sites, high cost, and limited storage create obstacles for the widespread application of traditional catalysts. Mono- or few-layer two-dimensional (2D) materials, with plenty of exposed chemisorption sites, easy, low-cost fabrication, and high conductivity show great potential as potential candidates to replace the traditional catalysts for water splitting [7,8,9,10]. Transition metal dichalcogenides have aroused attention among 2D materials due to their wide range of Nanomaterials 2021, 11, 3173.

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