Probing electrochemical CO2 reduction with in-situ/operando TEM

Electrochemical CO 2 reduction (CO 2 R) offers a promising route to convert greenhouse gas emissions into valuable chemicals, but challenges, such as low product selectivity, low current density, insufficient energy efficiency, and material instability, hinder its commercialisation. Addressing these issues requires a deep understanding of the working and degradation mechanisms of electrolysers. In-situ / operando transmission electron microscopy (TEM) offers a powerful method to clarify the structure-performance relationship at the nanoscale. This review critically examines recent advances in the application of in-situ / operando TEM to CO 2 R, highlighting how these techniques have revealed mechanisms underlying catalyst behaviour and degradation. We discuss current challenges in this research field, identify knowledge gaps, and propose future research directions. This work offers a fundamental understanding and some useful insights for researchers aiming to use advanced TEM to boost the development of CO 2 electrocatalysts.