Tailoring mass transfer on electrochemical fixation of air-abundant molecules

Electrochemical reduction of air-abundant molecules (e.g., CO₂, N₂, and O₂) offers a sustainable solution to address global energy and environmental challenges, where high current density and energy efficiency are highly desirable. However, commercially-relevant current density will cause dramatic change of cation, solvent, pH, and reactant molecular distribution near electrode, resulting in severe concentration polarization and sluggish reaction kinetics. In this case, mass transfer such as molecule migration pathway in electrolytes, electrodes, and devices need to be rationally designed and systematically optimized. Here this review will present a systematical introduction on regulating mass transfer on electrochemical fixation of air-abundant molecules. We firstly discuss the fundamental mass transport from bulk electrolyte to catalyst surface and within electric double layer (EDL) and review the recent advances in regulating mass transport behaviors and optimizing strategy of mass transfer on the catalytic surface. Then we compare the mass transport differences among different cell architectures combining with innovative prospect for transfer pathway towards breaking natural limitation of gas solubility over electroactive interfaces. It is expected that this review can inspire research on comprehensive understanding of fundamental mass transport mechanism at catalyst/electrolyte interface and shed light on optimizing the catalytical device towards practical application for electrochemical fixation of air-abundant molecules.