Electrochemical CO2 reduction (CO2R) is a promising technology for carbon recycling and energy storage. While gas-fed CO2R is currently the best practice because it facilitates fast mass transport, CO2R in water offers potential advantages such as avoiding salt formation, facile water control, and easier integration with CO2 capture. In this work, we enhance mass transport in an aqueous CO2 electrolyzer using fast pressure pulses (50 Hz, 1.2 bar) with a vibratory pump typically found in coffee machines. We demonstrate a limiting current density of 87 mA cm−2 toward CO2R products—nearly three times higher than without pulses. The current density can be further increased by leveraging the peak-to-peak pressure amplitude or pump frequency, as shown through particle image velocimetry (PIV) and an order-of-magnitude scaling analysis. Although challenges remain, such as pump energy consumption, contamination, heating, and pressure-wave damping, the pressure-pulsed concept is a promising direction for aqueous CO2R.

We demonstrate a hybrid electrolyzer design for CO₂electrolysis to multicarbon products using a cation exchange membrane and different electrode separations. Reducing the thickness of the catholyte flow field from 5 to 2.4 mm significantly decreases the cell voltage while maintaining longer-term stability.

Electrochemical carbon dioxide reduction to multi-carbon products such as ethylene and ethanol is a promising method to store electricity in chemical bonds and produce bulk chemicals from CO2. Simultaneous consideration of processes taking place at the molecular scale, electrolyser scale, and the process scale is crucial to efficiently move towards commercialization and avoid optimizing for unrealistic operating conditions. This chapter summarizes the relevant considerations at each vantage point and reviews the latest developments in CO2 reduction toward multi-carbon products at different scales.