Rational designing microenvironment of gas-diffusion electrodes via microgel-augmented CO₂ availability for high-rate and selective CO₂ electroreduction to ethylene

Efficient electrochemical CO₂ reduction reaction (CO₂RR) requires advanced gas-diffusion electrodes (GDEs) with tunned microenvironment to overcome low CO₂ availability in the vicinity of catalyst layer. Herein, for the first time, pyridine-containing microgels-augmented CO₂ availability is presented in Cu₂O-based GDE for high-rate CO₂ reduction to ethylene, owing to the presence of CO₂-phil microgels with amine moieties. Microgels as three-dimensional polymer networks act as CO₂ micro-reservoirs to engineer the GDE microenvironment and boost local CO₂ availability. The superior ethylene production performance of the GDE modified by 4-vinyl pyridine microgels, as compared with the GDE with diethylaminoethyl methacrylate microgels, indicates the bifunctional effect of pyridine-based microgels to enhance CO₂ availability, and electrocatalytic CO₂ reduction. While the Faradaic efficiency (FE) of ethylene without microgels was capped at 43% at 300 mA cm⁻², GDE with the pyridine microgels showed 56% FE of ethylene at 700 mA cm⁻². A similar trend was observed in zero-gap design, and GDEs showed 58% FE of ethylene at −4.0 cell voltage (>350 mA cm⁻² current density), resulting in over 2-fold improvement in ethylene production. This study showcases the use of CO₂-phil microgels for a higher rate of CO₂RR-to-C₂₊, opening an avenue for several other microgels for more selective and efficient CO₂ electrolysis.