In-situ imaging of strain-induced enhancement of hydrogen evolution activity on the extruded MoO₂ sheets

Strain engineering is a useful strategy for modifying the catalytic activity of electrocatalysts. However, in-situ visual characterization of the strain effect on the catalytic activity at nanoscale remains a huge challenge. Herein, we performed in-situ electrochemical scanning tunneling microscopy (EC-STM) imaging measurements at the local strained regions of extruded single-crystal molybdenum dioxide (MoO₂) sheets with combination of current noise analysis (n-EC-STM). The intensity-enhanced noise was observed at the local strained region compared to the unstrained regions in the same frame, which reveals the positive effect of compressive strain on the hydrogen evolution reaction (HER) activity of MoO₂ provided that the intensity of noise is positively correlated with catalytic HER Faradic current. Therefore, we clearly “see” the strain-induced enhancement of HER activity of MoO₂ at nanoscale by means of noise visualization. This work extends the visual characterization of strain engineering in electrocatalysis and related fields.