Scaling CO 2 Electrolyzer Cell Area from Bench to Pilot.

To contribute meaningfully to carbon dioxide (CO 2 ) emissions reduction, CO 2 electrolyzer technology will need to scale immensely. Bench-scale electrolyzers are the norm, with active areas <5 cm 2 . However, cell areas on the order of 100s or 1000s of cm 2 will be required for industrial deployment. Here, we study the effects of increasing cell area, scaling over 2 orders of magnitude from a 5 cm 2 lab-scale cell to an 800 cm 2 pilot plant-scale cell. A direct scaling of the bench-scale cell architecture to the larger area results in a ∼20% drop in ethylene (C 2 H 4 ) selectivity and an increase in the parasitic hydrogen (H 2 ) evolution reaction (HER). We instrument an 800 cm 2 electrolyzer cell to serve as a diagnostic tool and determine that nonuniformities in electrode compression and flow-influenced local CO 2 availability are the key drivers of performance loss upon scaling. Machining of an initial 800 cm 2 cell results in a standard deviation in MEA compression that is 7-fold that of a similarly produced 5 cm 2 cell (0.009 mm). Using these findings, we redesign an 800 cm 2 cell for compression tolerance and increased CO 2 transport and achieve an H 2 FE in the revised 800 cm 2 cell similar to that of the 5 cm 2 case (16% at 200 mA cm -2 ). These results demonstrate that by ensuring uniform compression and fluid flow, the CO 2 electrolyzer area can be scaled over 100-fold and retain C 2 H 4 selectivity (within 10% of small-scale selectivity).