Decoding complex product landscapes in CO2 electroreduction through SECM detection

The electrochemical carbon dioxide reduction reaction (CO 2 RR) often yields gaseous and liquid products simultaneously, making in situ, rapid, and distinguishable quantitative detection highly challenging due to product coexistence and signal overlap. To address this, we developed an electrochemical “fingerprint” collection and calibration framework suitable for multi-product CO 2 RR systems. Using Pt/Au ultramicroelectrodes, we record cyclic voltammograms across multiple scan rates to probe multicarbon alcohols in alkaline media and carboxylic acids in acidic media. The scan rate dependent current voltage responses were analyzed to identify characteristic potential and current features for each target species. After constructing calibration fingerprints for individual compounds, we resolved and validated the composite electrochemical features of binary and ternary multi-product systems with scanning electrochemical microscopy (SECM). By progressively advancing from single product systems to binary mixtures and ultimately to more realistic ternary product environments, we achieved effective discrimination of gas-liquid products under multi-component coexistence. This work establishes a detection and analysis workflow spanning from ultramicroelectrode-based CV calibration to SECM mixed-gas validation, providing a methodological foundation for process monitoring, rapid product identification, and qualitative analysis in complex, multiphase CO 2 RR systems.