Operando Imaging Reveals Active Wrinkled Regions for Hydrogen Evolution in MoS₂ Electrocatalysts

Under operando conditions, how local structural distortion influences electrocatalysis in non-metallic materials remains poorly understood, largely because charge-transfer processes and subsequent chemical steps are strongly coupled and difficult to disentangle experimentally. Here, by using operando atomic force microscopy-scanning electrochemical microscopy (AFM-SECM), we directly identify wrinkled regions in monolayer molybdenum disulfide (MoS₂) as highly active domains for the hydrogen evolution reaction (HER). Combined local AFM-SECM and scanning transmission electron microscopy (STEM) imaging further reveal that the enhanced activity is primarily localized at wrinkle edges, where folded edge structures are formed, providing spatially resolved evidence of a local structure-activity relationship. Interestingly, operando electron-transfer (ET) imaging reveals only limited enhancement of charge-transfer kinetics in these regions, indicating that the increased HER activity more likely arises from the promotion of subsequent chemical steps rather than from improved electron transfer. These findings provide mechanistic insight into the role of folded edge structures within wrinkled regions in non-metallic electrocatalysis and offer guidance for the rational design of high-performance electrocatalytic materials.