Hydrogen evolution activity of individual mono-, bi-, and few-layer MoS2 towards photocatalysis. (September 2017)

• Record Type: Journal Article
• Authors: Parzinger, Eric; Mitterreiter, Elmar; Stelzer, Max; Kreupl, Franz; Ager, Joel W.; Holleitner, Alexander W.; Wurstbauer, Ursula
• Is Part Of: Applied materials today. Volume 8(2017)
• Page Start: 132
• Page End: 140
• Publication Date: 2017-09
• Subjects: Transition metal dichalcogenide -- MoS2 -- HER -- Photocatalysis -- Electrochemical micro-cell; Materials science -- Periodicals; Materials -- Research -- Periodicals; 620.1105
• DOI: 10.1016/j.apmt.2017.04.007
• Languages: English
• ISSNs: 2352-9407

Abstract

Graphical abstract: Highlights: Hydrogen evolution activity of individual micromechanical exfoliated MoS2 crystals. Increasing hydrogen evolution activity of MoS2 with decreasing number of layers. Increasing HER activity under white-light illumination. Electrochemical investigation with in-situ optical access with μm lateral resolution. Abstract: We investigate the hydrogen evolution activity in the dark and under illumination above the band gap of individual mono-, bi- and few-layer (bulk) MoS2 flakes. We demonstrate that the electrocatalytic activity of 2H-MoS2 immersed in 1 M H2 SO4 increases with decreasing number of layers. For monolayers, we observe the highest exchange current density, which is one magnitude larger than in the bulk case. The onset potential scales with the number of layers, which is consistent with a previous report, suggesting that hopping transport across inter-layer barriers within the MoS2 flakes is responsible for this scaling. A specially designed micro-sized catalytic cell enables us to investigate individual MoS2 flakes with well-known geometry and edge-to-surface ratio. Taking these geometric parameters into account, we tentatively attribute the catalytic activity mainly to sulfur vacancies in the basal planes acting as active sites. The associated turn over frequencies (TOF) for mono- and bi-layer MoS2 yield values higher than 10 3 s −1 at an overpotential of −0.2 V vs. RHE. In view of light driven hydrogen evolution as a means of solar energy conversion, we investigate the photocatalytic activity of few-layer MoS2 under white light illumination.