Advances and challenges of carbon-free gas-diffusion electrodes (GDEs) for electrochemical CO₂ reduction

Electrochemical CO₂ reduction reaction (CO₂RR) coupled with renewable electricity holds promises for efficient mitigation of carbon emission impacts on the environment and turning CO₂ into valuable chemicals. One important task in CO₂RR development is the design and fabrication of efficient electrodes for stable operation in the long term. Gas-diffusion electrodes (GDEs) have been employed to continuously feed CO₂ to the electrolyzers. Despite significant advances in GDE design and tailoring GDE properties, the present GDEs often suffer from the critical issue of flooding due to the electrowetting of carbon-based substrates, which hinders the transition to industrial application. To address flooding, GDEs with intrinsically hydrophobic polymeric substrates have been recently fabricated and have shown promising performances. Herein, the advances and challenges associated with carbon-free GDEs are reviewed for CO₂RR. This review first briefly outlines GDE and electrolyzers basics. Through critical discussion around the shortcomings of conventional carbon-based GDEs, the most recent efforts to resolve flooding are summarized. Subsequently, the advances, advantages, and challenges of carbon-free GDEs are elaborated. Finally, priorities for future studies are suggested, with the aim to support the advancement and scale-up of carbon-free GDEs and extend them to other electrochemical systems where gas and the electrolyte are in contact.