Unsaturated Single Atoms on Monolayer Transition Metal Dichalcogenides for Ultrafast Hydrogen Evolution

Abstract

Large scale implementation of electrochemical water splitting for hydrogen evolution requires cheap and efficient catalysts to replace expensive platinum. Molybdenum disulfide is one of the most promising alternative catalysts but its intrinsic activity is still inferior to platinum. There is therefore a need to explore new active site origins in molybdenum disulfide with ultrafast reaction kinetics and to understand their mechanisms. Here, we report a universal cold hydrogen plasma reduction method for synthesizing different single atoms sitting on two-dimensional monolayers. In case of molybdenum disulfide, we design and identify a new type of active site, i.e., unsaturated Mo single atoms on cogenetic monolayer molybdenum disulfide. The catalyst shows exceptional intrinsic activity with a Tafel slope of 35.1 mV dec −1 and a turnover frequency of ~10 3 s-1 at 100 mV, based on single flake microcell measurements. Theoretical studies indicate that coordinately unsaturated Mo single atoms sitting on molybdenum disulfide increase the bond strength between adsorbed hydrogen atoms and the substrates through hybridization, leading to fast hydrogen adsorption/desorption kinetics and superior hydrogen evolution activity. This work shines fresh light on preparing highly-efficient electrocatalysts for water splitting and other electrochemical processes, as well as provides a general method to synthesize single atoms on two-dimensional monolayers.

Growth Mechanism of Alternating Defect Domains in Hexagonal WS2 via Inhomogeneous W‐Precursor Accumulation

“…2D transition-metal dichalcogenides (TMDs) have been intensively investigated for numerous unexplored physics and device applications. [1][2][3][4][5] Among the various methods for synthesizing TMD monolayers, chemical vapor deposition (CVD) has been widely used for high-quality TMD monolayers over a large area. [6][7][8][9] The optical and electrical properties of CVD-grown While a hexagonal WS 2 monolayer, grown by chemical vapor deposition, exhibits distinctive patterns in photoluminescence mapping, segmented with alternating S-vacancy (SV) and W-vacancy (WV) domains in a single crystal, the formation mechanism for native alternating defect domains remains unresolved to date.…”

“…2D transition‐metal dichalcogenides (TMDs) have been intensively investigated for numerous unexplored physics and device applications. [ 1–5 ] Among the various methods for synthesizing TMD monolayers, chemical vapor deposition (CVD) has been widely used for high‐quality TMD monolayers over a large area. [ 6–9 ] The optical and electrical properties of CVD‐grown TMDs are still limited by inherent point defects; vacancies of chalcogen and metal atoms are unavoidably generated in the crystal, and these vacancies play a key role in determining carrier scattering, [ 10 ] light‐emitting efficiency, [ 11,12 ] doping effects, [ 13 ] etc.…”

Recent advances in single metal atom-doped MoS2 as catalysts for hydrogen evolution reaction

“…Here, different synthetic strategies for single metal atom-doped MoS 2 are summarized and discussed ( Fig. 2a-f [36][37][38][39][40][41]).…”

“…In addition to thermal annealing, plasma treatment is another effective way for introducing single atoms, which shows a strong reducibility and the ability to dissociate chemical bonds between metal cations and anions at a low temperature in a metal complex to generate metal single atoms. For example, Luo et al [39] reported the synthesis of single metal atoms confined in MoS 2 monolayers by a cold hydrogen plasma reduction method (Fig. 2d).…”

Self‐Supported Mesoporous Iron Phosphide with High Active‐Site Density for Electrocatalytic Hydrogen Evolution in Acidic and Alkaline Media

“…In general, platinum (Pt) group materials are recognized as the benchmark HER electrocatalysts. However, the high cost, low earth abundance, and poor stability greatly hinder their widespread application [9–11] . Accordingly, it is extremely urgent to explore highly active and earth‐abundant electrocatalyst for HER.…”