Triple-phase interfaces for electrochemical reduction of carbon dioxide.

The CO2 electroreduction reaction (CO2RR) offers a promising approach for converting CO2 into valuable products, thereby storing renewable energy in chemical bonds and mitigating CO2 emissions. The process is fundamentally governed by the complex dynamics at the gas (CO2), liquid (H2O), and solid (catalyst) triple-phase interfaces (TPIs), where mass transport, charge transfer, and intermediate stabilization interact and compete. However, the practical performance of the CO2RR remains significantly below the threshold required for industrial applications, hindered by challenges such as liquid wetting, hydrophobic layer degradation, and electrowetting effects. In this context, we present a tutorial review that re-examines TPI paradigms by integrating early static models with recent dynamic experimental insights. Bridging macroscopic reactor design with atomic-scale interfacial dynamics necessitates the use of in situ/operando characterization techniques. We systematically review optimization strategies for TPIs (e.g., porous architectures, hydrophobic modifications, and heterostructure engineering) and analyze associated failure modes. Furthermore, we extend these concepts to other electrochemical reactions, including oxygen reduction and hydrogen evolution/oxidation, to extract universal principles that guide catalyst design. This review aims to provide a comprehensive framework for advancing the field of sustainable electrocatalysis and its future role in clean energy technologies.