Edge-Site Nanoengineering of WS₂ by Low-Temperature Plasma-Enhanced Atomic Layer Deposition for Electrocatalytic Hydrogen Evolution

Abstract

Edge-enriched transition metal dichalcogenides, such as WS 2 , are promising electrocatalysts for sustainable production of H 2 through the electrochemical hydrogen evolution reaction (HER). The reliable and controlled growth of such edge-enriched electrocatalysts at low temperatures has, however, remained elusive. In this work, we demonstrate how plasma-enhanced atomic layer deposition (PEALD) can be used as a new approach to nanoengineer and enhance the HER performance of WS 2 by maximizing the density of reactive edge sites at a low temperature of 300 °C. By altering the plasma gas composition from H 2 S to H 2 + H 2 S during PEALD, we could precisely control the morphology and composition and, consequently, the edge-site density as well as chemistry in our WS 2 films. The precise control over edge-site density was verified by evaluating the number of exposed edge sites using electrochemical copper underpotential depositions. Subsequently, we demonstrate the HER performance of the edge-enriched WS 2 electrocatalyst, and a clear correlation among plasma conditions, edge-site density, and the HER performance is obtained. Additionally, using density functional theory calculations we provide insights and explain how the addition of H 2 to the H 2 S plasma impacts the PEALD growth behavior and, consequently, the material properties, when compared to only H 2 S plasma.

Atomic Layer Deposition of Al-Doped MoS2: Synthesizing a p-type 2D Semiconductor with Tunable Carrier Density

“… 18 − 20 Synthesis of TMDs by atomic layer deposition (ALD) yields good quality material at relatively low-growth temperatures (<450 °C), as has been demonstrated by us and others. 21 − 23 Furthermore, ALD is known for its excellent thickness control, 19 , 21 , 22 , 24 uniformity, and it is inherently capable of conformally coating complex 3D structures. 21 , 25 , 26 …”

Atomic Layer Deposition of 2D Metal Dichalcogenides for Electronics, Catalysis, Energy Storage, and Beyond

“…FET [111] W(CO) 6 + H 2 S 165-205 20-40 nm (amorp.) LIB [263] 400 175 nm rough films (≈5 nm) Lubricant [264] [ 265] W(CO) 6 + H 2 S plasma 350 3-20 nm films (3-7 nm) HER, NIB [266] 350 20-60 nm rough films (3-10 nm) NIB [267] W(N t Bu) 2 (NMe 2 ) 2 + H 2 S 300 ≈5-50 nm rough films (≈10-30 nm) HER [268] W(N t Bu) 2 (NMe 2 ) 2 + H 2 S plasma 300 ≈8-65 nm rough films (≈10-20 nm) HER [269] so far. On the other hand, there is still a need for even new MoS 2 processes with good ALD characteristics that produce smooth, high-quality films at low temperatures, for example.…”

“…≈6 nm rough films (14 ± 1 nm) -2020 [107] 250 (450, H 2 S) ≈2-3 ML films (≈10 nm) -2020 [121] W(N t Bu) 2 (NMe 2 ) 2 + H 2 S plasma + Ar plasma 450 ≈6 nm rough films (24 ± 2 nm) -2020 [107] W(N t Bu) 2 (NMe 2 ) 2 + H 2 S plasma + H 2 plasma 450 ≈6 nm rough films (19 ± 1 nm) --2020 [107] W(N t Bu) 2 (NMe 2 ) 2 + H 2 /H 2 S plasma 300 ≈8-65 nm rough films (≈10-50 nm) HER 2019 [269] W 2 (NMe 2 ) 6 + H 2 S 150 (400, H 2 S) ≈2-15 ML films (as-dep. amorp., ann.…”

Manipulating Interfaces of Electrocatalysts Down to Atomic Scales: Fundamentals, Strategies, and Electrocatalytic Applications

“…[ 59 ] Specifically, the local density, types, locations, and stability of defects at interfaces need to be precisely controlled to obtain the key understanding in the correlation between the defects and the activity on each type of the defect sites, and even the synergistic function of multiple types of defects, thereafter building up the general design rules for defect engineering. [ 3 ] To this end, new control methods of defect engineering, especially the precise synthesis methods down to atomic scales such as atomic layer deposition, [ 139,148 ] are vital to be developed and investigated. [ 145 ] Furthermore, to help control the defects and investigate the defect stability, operando characterization techniques that allow real‐time observation of the defects during the electrocatalytic process, are essential to be employed and further advanced.…”