Pitfalls and Protocols: Evaluating Catalysts for CO₂ Reduction in Electrolyzers Based on Gas Diffusion Electrodes

The evaluation of catalysts on gas diffusion electrodes (GDEs) have propelled the progress of electrochemical CO 2 reduction reaction (CO 2 RR) at industry-relevant activities. However, high experimental complexities exist in GDE-based flow electrolyzers, whereby various experimental factors can influence the evaluation of catalytic CO 2 RR performances. Not accounting for these experimental factors could result in inconsistent conclusions and thus hinder rational catalyst developments. This Perspective highlights a range of experimental factors that can affect the performance metrics for electrocatalysts. Specifically, the product faradaic efficiency can be influenced by the overestimation of the effluent gas flow rate, unaccounted losses of products, and unintended alteration of microenvironments. In addition, cathodic voltage can be inaccurately determined due to the unaccounted dynamic changes in uncompensated resistance. By raising awareness of these potential pitfalls and establishing appropriate protocols, we foresee a more meaningful benchmarking of catalytic performances across the literature.