Engineering Substrate Interaction To Improve Hydrogen Evolution Catalysis of Monolayer MoS₂ Films beyond Pt

Abstract

MoS 2 holds great promise as a cost-effective alternative to Pt for catalyzing the hydrogen evolution reaction (HER) of water, but its reported catalytic efficiency is still worse than that of Pt, the best HER catalyst but too rare and expensive for mass production of hydrogen. We report a strategy to enable the catalytic activity of monolayer MoS 2 films that are even better than that of Pt via engineering the interaction of the monolayer with supporting substrates. The monolayer films were grown with chemical vapor deposition processes and controlled to have an optimal density (7− 10%) of sulfur vacancies. We find that the catalytic activity of MoS 2 can be affected by substrates in two ways: forming an interfacial tunneling barrier with MoS 2 and modifying the chemical nature of MoS 2 via charge transfer (proximity doping). Following this understanding, we enable excellent catalytic activities at the monolayer MoS 2 films by using substrates that can provide ndoping to MoS 2 and form low interfacial tunneling barriers with MoS 2 , such as Ti. The catalytic performance may be further boosted to be even better than Pt by crumpling the films on Ti coated flexible polymer substrates, as the Tafel slope of the film is substantially decreased with the presence of crumpling-induced compressive strain. The monolayer MoS 2 films show no degradation in catalytic performance after being continuously tested for over 2 months.

Review on Synthesis and Catalytic Coupling Mechanism of Highly Active Electrocatalysts for Water Splitting

“…The CVD method controls the density and thickness of the coating by controlling the temperature and pressure, thereby obtaining a high‐quality and uniform electrolysis water catalyst. For example, Li et al [ 50 ] used CVD to grow monolayer and control the optimal density of its sulfur vacancy (7–10%). First, MoCl 5 and S are used as precursors to be placed upstream, and argon atmosphere is introduced.…”

Strategies to improve electrocatalytic and photocatalytic performance of two-dimensional materials for hydrogen evolution reaction

“…Intrinsic defects involve the deviation of the local stoichiometry of a constituent species of a material from the overall stoichiometry of the material [157]. Defects can be divided into disorders, vacancies, and grain boundaries [158]; among these, vacancies are most commonly investigated. Moreover, vacancies can be divided into sulfur vacancies, oxygen vacancies, carbon vacancies, nitrogen vacancies, etc.…”

“…Many physical and optical properties of MoS2 are related to the matrix [211,212]. Proper use mechanism can result in electrocatalytic performance that exceeds that of precious metals [158]. However, in the study of matrix effects, it is easy to be limited by previous research results.…”

[Mo2O2S8]2− small molecule dimer as a basis for hydrogen evolution reaction (HER) catalyst materials

“…To pursue the first approach involving enhanced site activity, metal dopants have been used to optimize ΔG for hydrogen adsorption at molybdenum sulfide edges [13,14]. Moreover, proton accessibility and electrical conductivity to those edges have been improved by forming ultrathin layers [15][16][17][18] and composites with conductive materials [19][20][21][22][23], respectively. In terms of the second approach regarding site density, work has largely centered on replacing typically sheet-like and crystalline MoS 2 with new morphologies.…”