Scaling CO₂ Electrolyzer Cell Area from Bench to Pilot

Abstract

To contribute meaningfully to carbon dioxide (CO₂) emissions reduction, CO₂ electrolyzer technology will need to scale immensely. Bench-scale electrolyzers are the norm, with active areas <5 cm². However, cell areas on the order of 100s or 1000s of cm² will be required for industrial deployment. Here, we study the effects of increasing cell area, scaling over 2 orders of magnitude from a 5 cm² lab-scale cell to an 800 cm² pilot plant-scale cell. A direct scaling of the bench-scale cell architecture to the larger area results in a ∼20% drop in ethylene (C₂H₄) selectivity and an increase in the parasitic hydrogen (H₂) evolution reaction (HER). We instrument an 800 cm² electrolyzer cell to serve as a diagnostic tool and determine that nonuniformities in electrode compression and flow-influenced local CO₂ availability are the key drivers of performance loss upon scaling. Machining of an initial 800 cm² cell results in a standard deviation in MEA compression that is 7-fold that of a similarly produced 5 cm² cell (0.009 mm). Using these findings, we redesign an 800 cm² cell for compression tolerance and increased CO₂ transport and achieve an H₂ FE in the revised 800 cm² cell similar to that of the 5 cm² case (16% at 200 mA cm^-2). These results demonstrate that by ensuring uniform compression and fluid flow, the CO₂ electrolyzer area can be scaled over 100-fold and retain C₂H₄ selectivity (within 10% of small-scale selectivity).