The scientists optimized the catalyst microenvironment in this work by employing mixed CO/CO2 feeds that were characteristic of waste gases from steel plants and partial industrial combustion of fossil fuels. They specifically explored CO/CO2 co-electrolysis in an alkaline membrane electrode assembly (MEA) electrolyzer at high current densities over a nanoporous CuO nanosheet catalyst.
With increasing CO pressure in the feed, the major product gradually shifted from ethylene to acetate and the current density remarkably increased, up to 3.0 A cm-2 under 0.6 MPa pure CO feed.
Guoxiong Wang, Professor, Dalian Institute of Chemical Physics, Chinese Academy of Sciences
Prof. Gao states, “The selectivity switch was induced by *CO coverage and local pH. Ethylene was preferentially generated at low *CO coverage, whereas acetate formation was favorable at high *CO coverage and high local pH.”
The scientists improved electrolysis performance even further by improving electrolysis conditions. The Faradaic efficiency and partial current density of C2+ products were 90.0% and 3.1 A cm-2, respectively, equating to 100.0% carbon selectivity and 75.0% yield, exceeding thermocatalytic CO hydrogenation.
The CO electrolysis process was scaled up using a stack of four 100 cm2 MEAs, with the greatest ethylene synthesis rate of 457.5 mL min-1 at 150 A and acetate formation rate of 2.97 g min-1 at 250 A.
Our work highlights the promise of tuning catalyst microenvironments for selective production of single C2+ products such as acetate and ethylene, and presents an effective scale-up demonstration of high-rate CO2/CO electrolysis towards practical application.
Guoxiong Wang, Professor, Dalian Institute of Chemical Physics, Chinese Academy of Sciences
Journal Reference:
Wei, P., et al. (2023) Coverage-driven selectivity switch from ethylene to acetate in high-rate CO2/CO electrolysis. Nature Nanotechnology. doi.org/10.1038/s41565-022-01286-y.