CO electrolysis to multicarbon products over grain boundary-rich Cu nanoparticles in membrane electrode assembly...

Producing valuable chemicals like ethylene via catalytic carbon monoxide conversion is an important nonpetroleum route. Here we demonstrate an electrochemical route for highly efficient synthesis of multicarbon (C₂₊) chemicals from CO. We achieve a C₂₊ partial current density as high as 4.35 ± 0.07 A cm^-2 at a low cell voltage of 2.78 ± 0.01 V over a grain boundary-rich Cu nanoparticle catalyst in an alkaline membrane electrode assembly (MEA) electrolyzer, with a C₂₊ Faradaic efficiency of 87 ± 1% and a CO conversion of 85 ± 3%. Operando Raman spectroscopy and density functional theory calculations reveal that the grain boundaries of Cu nanoparticles facilitate CO adsorption and C - C coupling, thus rationalizing a qualitative trend between C₂₊ production and grain boundary density. A scale-up demonstration using an electrolyzer stack with five 100 cm² MEAs achieves high C₂₊ and ethylene formation rates of 118.9 mmol min^-1 and 1.2 L min^-1, respectively, at a total current of 400 A (4 A cm^-2) with a C₂₊ Faradaic efficiency of 64%.