High‐Concentration Alcohol Generation in Bipolar Membrane CO Electrolyzer

TL;DR

A new CO electrolyzer design significantly reduces product dilution and increases alcohol production efficiency.

Contribution

A forward-biased bipolar membrane system and catalyst engineering to enhance alcohol production from CO.

Findings

FB-BPM system reduces liquid product crossover to <10%, 8x lower than conventional systems.

CuSn catalyst enhances alcohol production with >15 wt% yield directly from the cathode outlet.

Abstract

Electrochemical reduction of carbon dioxide and carbon monoxide offers an electricity‐powered route to make multicarbon liquid products. However, in conventional systems employing anion exchange membranes (AEMs), significant liquid product crossover leads to dilute product streams, increasing separation costs; and also produces unwanted anodic oxidation, further decreasing overall efficiency. Here, we report a forward‐biased bipolar membrane (FB‐BPM) system that achieves <10% liquid product crossover while sustaining a highly alkaline environment near the cathode, suppressing ethylene and hydrogen and favoring liquid products. By tuning catalyst composition to modulate the adsorption of *H and *OH, we steer selectivity toward acetate and alcohols. Using the FB‐BPM system, we achieve >25 wt% acetate on CuZn and >15 wt% alcohols on CuSn directly from the cathode outlet stream.

This study presents a forward‐biased bipolar membrane (FB‐BPM) CO electrolyzer that reduces liquid product crossover to <10% (8x lower than conventional designs) while minimizing hydrogen production and in favor of multicarbon liquid species. By engineering catalyst morphology to modulate the binding of *CO, *H, and *OH intermediates, we identified a CuSn catalyst enhancing C2–C1 coupling pathways for alcohols formation. Integrating the reactor design with catalyst innovation, we achieve >15 wt% alcohols production directly from the cathodic outlet.

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