Scaling CO<sub>2</sub> Electrolyzer Cell Area from Bench to Pilot
Vivian E. Nelson, Colin P. O’Brien, Jonathan P. Edwards, Shijie Liu, Christine M. Gabardo, Edward H. Sargent, David Sinton
Abstract
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).