Gas diffusion electrodes, reactor designs and key metrics of low-temperature CO2 electrolysers

CO2 emissions can be recycled via low-temperature CO2 electrolysis to generate products such as carbon monoxide, ethanol, ethylene, acetic acid, formic acid and propanol. In recent years, progress has been made towards an industrially relevant performance by leveraging the development of gas diffusion electrodes (GDEs), which enhance the mass transport of reactant gases (for example, CO2) to the active electrocatalyst. Innovations in GDE design have thus set new benchmarks for CO2 conversion activity. In this Review, we discuss GDE-based CO2 electrolysers, in terms of reactor designs, GDE composition and failure modes, to identify the key advances and remaining shortfalls of the technology. This is combined with an overview of the partial current densities, efficiencies and stabilities currently achieved and an outlook on how phenomena such as carbonate formation could influence the future direction of the field. Our aim is to capture insights that can accelerate the development of industrially relevant CO2 electrolysers. Chemicals and fuels can be generated from CO2 via electrolysers that employ gas diffusion electrodes (GDEs). In this Review, the authors consider promising catalysts and reactors—and how these fail—to identify key advances and remaining gaps in the development of industrially relevant GDE-based CO2 electrolysers.