Kilowatt-scale CO electroreduction enabled by cation-induced double-layer rigidity control

Abstract

Scaling up CO electrolyzers to the pilot scale is a crucial stepping stone to commercializing this emerging carbon utilization technology. The dilemma between high product Faradaic efficiency (FE) and high current density is a critical hurdle in this path. Here, we link this trade-off to the electric double-layer (EDL) rigidity controlled by alkali cation concentrations in a volcano-type relationship. This understanding leads us to devise an effective EDL rigidity regulation method by incorporating a porous carbon black (CB) layer on top of the catalyst layers (CLs). As a result, we report FEs of ~85% for multi-carbon (C2+) products at 700 mA cm -2 in a 5-cm 2 zero-gap electrolyzer using Cu electrodes with 12-μm carbon layers. We devise kilowattscale electrolyzer stacks with a total effective area of up to 6×50 cm 2 and document 150-h stable electrolysis at 20 A without compromising C2+ product FEs.