Vertically Aligned Ultrathin 1T-WS2 Nanosheets Enhanced the Electrocatalytic Hydrogen Evolution

Abstract

Efficient evolution of hydrogen through electrocatalysis holds tremendous promise for clean energy. The catalytic efficiency for hydrogen evolution reaction (HER) strongly depends on the number and activity of active sites. To this end, making vertically aligned, ultrathin, and along with rich metallic phase WS₂ nanosheets is effective to maximally unearth the catalytic performance of WS₂ nanosheets. Metallic 1T polymorph combined with vertically aligned ultrathin WS₂ nanosheets on flat substrate is successfully prepared via one-step simple hydrothermal reaction. The nearly vertical orientation of WS₂ nanosheets enables the active sites of surface edge and basal planes to be maximally exposed. Here, we report vertical 1T-WS₂ nanosheets as efficient catalysts for hydrogen evolution with low overpotential of 118 mV at 10 mA cm^-2 and a Tafel slope of 43 mV dec^-1. In addition, the prepared WS₂ nanosheets exhibit extremely high stability in acidic solution as the HER catalytic activity and show no degradation after 5000 continuous potential cycles. Our results indicate that vertical 1T-WS₂ nanosheets are attractive alternative to the precious platinum benchmark catalyst and rival MoS₂ materials that have recently been heavily scrutinized for hydrogen evolution. Vertical 1T-WS2 for hydrogen evolution.

Keywords: Electrocatalysis; Hydrogen evolution reaction; Metallic 1T phase; WS2 nanosheets.

Fig. 1

a–b Top-down SEM image of the prepared vertical 1T-WS₂ nanosheets on Ti substrate. c–d HAADF-STEM of 1T-WS₂ nanosheets

Fig. 2

HAADF-STEM image (a) and corresponding elemental mapping (b for S, c for W, d for S and W) for the 1T-WS₂ nanosheets

Fig. 3

HRTEM image of a vertical 1T-WS₂ nanosheets and b, c false-color images responding to the amplification of a. Intensity profiles along the light-blue line indicated in image b is shown in image d

Fig. 4

XPS spectra of W 4f (a) and S 2p (b) binding energy of vertical 1T-WS₂ nanosheets

Fig. 5

a Raman spectrum of vertical 1T-WS₂ nanosheets. b Schematics of preferentially excited A¹_g Raman mode for edge-terminated nanosheets (top) and E¹_2g mode for terrace-terminated nanosheets (bottom)

Fig. 6

a Polarization curves and b Tafel plots of Pt/C, WS₂ nanosheets, and vertical 1T-WS₂ nanosheets in 0.5 M H₂SO₄ at a scan rate of 5 mV/s. c Durability test showing negligible current loss even after 5000 CV cycles and d time dependence of the current density curve at an overpotential of 160 mV versus RHE for vertical 1T-WS₂ nanosheets (no iR compensation)