Nutrient diffusion-inspired catalysts with self-reinforced concentration gradient for sustainable electroreduction of dilute CO(2).

The electrocatalysis of flue gas into CO in membrane electrode assembly (MEA) provides a sustainable route for realizing practical CO(2) electrolysis technology but suffers from restricted CO(2) mass transport due to thick gas boundary layer (GBL) and weak concentration gradient. Inspired by nutrient diffusion mechanism in plant, we introduce the concept of self-reinforced CO(2) concentration gradient, which is realized via porous carbon nanosheets (PC) as soil for enriching CO(2) and single-atomic Ni-doped carbon nanotubes (Ni-CNTs) as rhizome for electro-catalyzing CO(2). A combined experimental and simulation study reveals optimal length of Ni-CNTs on PC reduces the GBL thickness and spontaneously enhances CO(2) concentration gradient, synergistically breaking the limitation of CO(2) transport. Consequently, the CO Faradaic efficiency attains >90% with varying CO(2) concentration of 4-15 vol. % CO(2) in MEA. Further through incorporation of an O(2)-adsorption packed column before MEA, we realize the stable and selective conversion of O(2)-containing flue gas into CO.