Enhanced Catalytic Activity in Strained Chemically Exfoliated WS2 Nanosheets for Hydrogen Evolution

TL;DR

This study demonstrates that chemically exfoliated WS2 nanosheets with strained metallic 1T phase exhibit enhanced catalytic activity for hydrogen evolution, offering a promising, cost-effective alternative to platinum-based catalysts.

Contribution

The paper introduces atomically thin WS2 nanosheets with a high concentration of strained 1T phase, significantly improving HER catalytic performance compared to existing materials.

Findings

Strained 1T phase correlates with higher catalytic activity.

Exfoliated WS2 nanosheets show very low overpotentials for HER.

Density functional theory indicates strain increases density of states at Fermi level.

Abstract

The ability to efficiently evolve hydrogen via electrocatalysis at low overpotentials holds tremendous promise for clean energy. Hydrogen evolution reaction (HER) can be easily achieved from water if a voltage above the thermodynamic potential of the HER is applied. Large overpotentials are energetically inefficient but can be lowered with expensive platinum based catalysts. Replacement of Pt with inexpensive, earth abundant electrocatalysts would be significantly beneficial for clean and efficient hydrogen evolution. Towards this end, promising HER characteristics have been reported using 2H (trigonal prismatic) XS2 (where X = Mo or W) nanoparticles with a high concentration of metallic edges as electrocatalysts. The key challenges for HER with XS2 are increasing the number and catalytic activity of active sites. Here we report atomically thin nanosheets of chemically exfoliated WS2 as efficient catalysts for hydrogen evolution with very low overpotentials. Atomic-resolution transmission electron microscopy and spectroscopy analyses indicate that enhanced electrocatalytic activity of WS2 is associated with high concentration of strained metallic 1T (octahedral) phase in the as-exfoliated nanosheets. Density functional theory calculations reveal that the presence of strain in the 1T phase leads to an enhancement of the density of states at the Fermi level and increases the catalytic activity of the WS2 nanosheet. Our results suggest that chemically exfoliated WS2 nanosheets could be interesting catalysts for hydrogen evolution.