Evaluating the Stability of Oxide‐Derived Cu─Sn Catalysts for CO 2 Reduction in Zero‐Gap Electrolyzers

Bimetallic electrocatalysts hold substantial potential for scaling up CO 2 electroreduction, yet their practical deployment is hindered by a persistent gap between conventional three‐electrode testing and industrially relevant electrolyzer conditions. In this study, we employed an oxide‐derived Cu─Sn catalyst with a high CO Faradaic efficiency (FE) of 92.4% as a model catalyst to evaluate the electrochemical stability under realistic zero‐gap CO 2 electrolyzers. During extended operation, the FE of CO gradually decreased before stabilizing after approximately 48 h, reaching a CO‐to‐formate ratio close to 1:1. In‐situ and quasi‐in‐situ spectroscopic analyses revealed that this shift in selectivity correlates with the partial transformation of the catalyst into a Cu 6 Sn 5 alloy. To remediate this performance loss and regenerate the active state, an in‐situ cyclic voltammetry (CV) protocol was applied to re‐oxidize the metallic components, effectively reversing the alloying process and restoring the high CO selectivity. This work correlates the oxidation state of Cu─Sn with its catalytic behavior in zero‐gap electrolyzers, and demonstrates a practical recovery protocol to enhance operational stability, highlighting the potential of dynamic catalyst management for industrial CO 2 electrolysis.