(666c) Identifying and Alleviating the Potential-Dependent Flooding Challenges for Energy-Efficient CO(2) Conversion to Multicarbon Products

Electrochemical CO₂/CO reduction (CO₍₂₎R) to multicarbon (C₂₊) products has drawn significant attention as a promising route for the generation of sustainable fuels and chemicals^[1]. However, due to the complex nature of CO₍₂₎R, achieving high energy efficiency (EE), especially at high current densities, remains a challenge, greatly hindering the practical implementation of this technology^[2]. By carefully analyzing recent state-of-the-art CO₂R data, we found that lowering the applied potential plays a critical role in maintaining the stability of the reaction layer during CO₂R, particularly in preventing electrode flooding. Therefore, if a catalyst candidate can afford a sufficient CO₂R current with a small applied potential, we can anticipate significantly enhanced CO₂R stability, concurrently, enhanced EE at high current densities. To validate this hypothesis, we developed a CuGa bimetallic catalyst with notably reduced activation energy for multi-carbon product formation. The low activation overpotential allows us to achieve practical relevant current densities (≥ 1.0 𝐴 𝑐𝑚^−2) for CO₂ reduction at low overpotentials, ensuring the stability of the catalyst layer and minimizing concentration overpotential. As a result, the optimized CuGa catalyst attains over 50% cathodic energy efficiency for multi-carbon production at a high current density exceeding 1.0 𝐴 𝑐𝑚^−2. Furthermore, Cu₅Ga₁-GDE demonstrated ~90% Faradaic Efficiency towards C₂₊ products at an industrial relevant current density (0.3 𝐴 𝑐𝑚^−2) for more than 120 hours, while the reference Cu-GDE only last for 20 hours under identical conditions. Moreover, using this CuGa catalyst, we achieved current densities exceeding 2.0 𝐴 𝑐𝑚^−2 in a zero-gap membrane electrode assembly-based (MEA) reactor, with a full-cell energy efficiency surpassing 30%. Overall, the correlation between the electrode potential and the stability of the reaction interface, along with the strategy proposed in this study, opens a pathway for the energy-efficient electrosynthesis of C₂₊ products from CO₂.