MXene, a family of two-dimensional (2D) transition metal carbides and nitrides, has intriguing electrochemical energy storage and electrocatalysis applications. Introducing the electronic metal–support interaction (EMSI) effect is one effective strategy to optimize the catalytic efficiency for MXene-based composites. However, most of the studies concentrate on optimizing the performance of metals rather than supported substrates by using this strategy. In this work, we mainly investigate the influence of an EMSI effect on the performance of the supported substrate (Ti₃C₂T_x MXene). Detailed scanning electrochemical microscopy and numerical simulations results reveal that the charge distribution on the Ti₃C₂T_x basal plane (approximate 100 nm-radius) surrounding Au nanoparticles (20 nm-radius) was significantly enhanced as a result of –O being the majority surface functional group on Ti₃C₂T_x that was attached to Au nanoparticle, and the related hydrogen evolution reaction (HER) activity was much better than that of the unaffected Ti₃C₂T_x basal plane, which even can be comparable to that of Au. This finding will be helpful for designing new strategies to enhance the overall catalytic performance of various MXene-based composites.

Scanning electrochemical microscopy (SECM) is an attractive technology to in-situ characterize the structural evolution and catalytic performance for various electrocatalysts. However, spatial and temporal resolution coupling are still the obstacles that limit its wide applications. Herein, a new operation mode, Fast Scan mode, was developed by improving the dual-pass scan mode, designing novel hardware structure, and employing thermal drift calibration software to achieve a high spatial and temporal resolution simultaneously. The temporal speed can achieve 4 Hz for a high spatial resolution (less than 30 nm) image. This operation mode was employed to dynamically track the phase transition process of molybdenum disulfide (MoS₂) over time and characterize the hydrogen evolution reaction (HER) catalytic activity on the edge of semiconducting MoS₂ quantitatively while minimizing the diffusional broadening effect and total amount of catalytic products generated above the surface. This new approach should be useful for in-situ tracking dynamic electrochemical processes, establishing the structure-activity relationship for structural complex electrocatalysts, and offering a strategy for high-speed scanning with other electrochemical imaging techniques.