Probing Electrochemical CO₂ Reduction: Insights from in Situ Scanning Probe Microscopy

Electrochemical CO₂ reduction (CO₂RR) is a pivotal pathway towards sustainable energy storage and carbon neutrality, yet its efficiency and selectivity are governed by intricate interfacial processes at the nanoscale. This review systematically summarizes the latest advancements in scanning probe microscopy (SPM) techniques for elucidating CO₂RR mechanisms. First, we describe the principles and applications of key in situ SPM methods in CO₂RR, including scanning electrochemical microscopy (SECM) for mapping local reactant distribution, scanning electrochemical cell microscopy (SECCM) for probing the active sites, in situ electrochemical scanning tunneling microscopy (EC-STM) for atomic-scale catalyst surface imaging, and electrochemical atomic force microscopy (EC-AFM) for reaction-induced surface reconstruction. Case studies demonstrate how these techniques can be used to decode the nanoscale localized properties of catalysts. By critically examining the mechanistic understanding, we explicitly link these findings to the rational design of next-generation catalysts. Ultimately, we critically discuss challenges in spatiotemporal resolution and future directions, including ultrafast SPM for transient intermediates and AI-driven multimodal data analysis. This review emphasizes the transformative role of SPM in bridging the gap between macroscopic performance and molecular-level insights for designing next-generation CO₂RR catalysts.