Path-dependent hydrogen evolution reaction via selective etching of bilayer MoS2 catalysts

Abstract

Molybdenum disulfide (MoS₂) is being considered as a promising candidate for replacing noble metal catalysts in the hydrogen evolution reaction (HER). However, low active site density, semiconducting properties, and electrochemically inert basal planes limit the catalytic performance of MoS₂ catalysts. Therefore, various strategies have been developed for activating basal planes in MoS₂ catalysts. Here, we propose an efficient laser technology for activating basal planes and creating controlled artificial patterns. The precisely controlled laser etching technique allows for etching only the top layer of the bilayer MoS₂ catalyst, and using this technique, the appropriately etched area increases the active sites without any degradation of catalytic performance, enabling efficient carrier injection. The catalytic behavior of line patterned MoS₂ exhibited line density dependent catalytic performance. Compared with pristine MoS₂ catalysts, the etched catalysts with 5 lines in a specific area (L5-MoS₂) showed a decreased overpotential and Tafel slope up to 65.1% and 73.7%, respectively. Moreover, in the case of L5-MoS₂ devices, the vertical contact between the etched line and electrode exhibited improved catalytic performance with a low Tafel slope and charge transfer resistance, which is mainly attributed to the facilitated charge transfer induced rapid charge exchange process at the electrolyte/catalyst interface. This effective strategy proposes a controllable defect engineering technique for improving the catalytic performance in 2D TMDC catalysts.