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.

Ag nanowire (NW) film is the promising next generation transparent conductor. However, the residual long-chain polyvinylpyrrolidone (PVP, introduced during the synthesis of Ag NWs) layer greatly deteriorates the carrier transport capability of the Ag NW film and as well its long-term stability. Here, we report a one-step I⁻ ion modification strategy to completely replace the PVP layer with an ultrathin, dense layer of I⁻ ions, which not only greatly diminishes the resistance of the Ag NW film itself and that at interface of the Ag NW film and a functional layer (e.g., a current collect electrode) but also effectively isolates the approaching of corrosive species. Consequently, this strategy can simultaneously improve the carrier transport properties of the Ag NW film and its long-term stability, making it an ideal electric component in diverse devices. For example, the transparent heater and pressure sensor made from the I⁻-wrapped Ag NW film, relative to their counterparts made from the PVP-wrapped Ag NW film, deliver much improved heating performance and pressure sensing performance, respectively. These results suggest a facile post treatment approach for thin Ag NW film with improved carrier transport properties and long-term stability, thereby greatly facilitating its downstream applications.