Directed Evolution of Pre-Catalyst Improves Pulsed-Electrochemical Conversion of CO 2 to Ethanol-Rich Crude

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Bicarbonate electrolysis enables direct conversion of dissolved CO₂ from capture solutions, presenting a low-energy alternative to conventional gas-fed CO₂ electrolysis systems by eliminating the need for CO₂ regeneration, purification, and pressurization. However, CO₂ mass transport limitations and pH-induced CO₂ depletion near the catalyst–electrolyte interface restrict its efficiency and selectivity, particularly at industrially relevant current densities. We report a pulsed electrolysis strategy integrated with in-situ activation of Cu₂O/Cu mesh pre-catalysts, enabling the stabilization of mixed-valence copper species under dynamic operating conditions. A custom-designed six-segment pulse waveform (with 4 s pulse width) promotes Cu⁺ oxide formation and subsequent reduction to metallic Cu⁰, generating locally alkaline conditions that facilitate C–C coupling and steer selectivity toward C₂+ products. This approach achieves a Faradaic efficiency (FE) of 72% for C₂+ products, including 39% for ethanol and 52% for total liquid products, at an applied current density of 150 mA/cm² and a cathodic potential of –1.1 V vs RHE. In-situ cyclic voltammetry reveals reversible Cu²⁺/Cu⁺ transitions, while ex-situ characterization confirms post-electrolysis catalyst stability. A 1D electrochemical model highlights the dynamic modulation of local pH and CO₂ gradients under pulsed operation, offering mechanistic insight into the improved C–C coupling kinetics. This work underscores the potential of combining pre-catalyst evolution with pulse-engineered electrolysis as a scalable pathway toward selective and energy-efficient CO₂-to-C₂+ conversion in bicarbonate media. Figure 1

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