Fig. 4: Ethylene carbonate synthesis using a gas diffusion electrode and flow cell.

a Average indirect Faradaic efficiency values of ethylene carbonate at 10 mA/cm² current density using three different compositions of gas (1.5%, 15%, and 100% CO₂, the mixed gases were balanced with N₂), different CO₂ supply methods, and cell constructions. The left columns of each group show the EC iF.E. values in an H-cell, where CO₂ was supplied by injecting it with a needle for 25 min at a gas flow rate of 200 sccm. The right columns of each group show the EC iF.E. values in a flow cell, where CO₂ was supplied by permeating gas through the GDE at a gas flow rate of 20 sccm. Despite the smaller amount of supplied CO₂, EC iF.E. values were higher when using the gas diffusion method. Each point was repeatedly measured three times, and the error bars indicate standard deviation. b Schematic depiction of the flow cell components. The components are stacked without gap in a real operation. While 0.5 M TBACl-2-chloroethanol solution cycles through the catholyte path, gas is supplied into the solution by permeating through a Ni-sputtered PTFE film GDE (green arrow). c Average indirect Faradaic efficiency values of ethylene carbonate at three different current densities (10, 25, 50 mA/cm²) and two different compositions of gas (100%, 15% CO₂). The gas was supplied at a gas flow rate of 20 sccm during the electrolysis. EC iF.E. value decreases when the rate of electron supply exceeds the supply of CO₂. Each point was repeatedly measured three times, and the error bars indicate standard deviation. d Left axis indicates concentration in the catholyte and indirect Faradaic efficiency values for EC by cell operation time, using 15% CO₂ gas, at a current density of 50 mA/cm². EC concentration linearly increases up to 0.09 M during 5 hours of electrolysis. EC iF.E. value maintains around 45%, indicating operational stability. Right axis indicates the overall cell voltage during operation. The voltage was not iR-corrected. Source data for Fig. 4a, c, d are provided as a Source Data file.