CO2 reduction in a microchannel electrochemical reactor with gas-liquid segmented flow

Electrochemical CO2 reduction is suffered from mass transfer limitation at high current densities, owing to the low carbon dioxide concentration over the surface of the catalyst. To enhance mass transfer, a novel annular microchannel electrochemical reactor was established, which consists of a cylindrical cation exchange membrane at the outside and an oxide-derived Cu foam rod as the electrode in the middle. The results show that, due to the enhanced gas–liquid mass transfer of CO2 in the channel, the limiting current density can increase by 49.3% from 6.7 mA cm−2 to 10.0 mA cm−2 and CO2 reduction rate increase by 55.3% from 21.5 × 10−9mol s−1 cm−2 to 33.4 × 10−9mol s−1 cm−2, compared when Cu electrode is in the open space. It further shows the limiting current density is influenced by the annulus channel width and gas–liquid ratio, and width of 1 mm gives the best performance at a gas–liquid ratio of 2:1. This work demonstrates the great potential of utilizing microchannel to intensify the mass transfer for efficient electrochemical CO2 reduction.