Accelerate Mass Transport of Proton and Carbon Sources by Super‐Hygroscopic and Porous Nanosheets for Continuous CO₂‐To‐Ethylene Upgrade

Abstract Gas‐water/catalyst triple‐phase interface and the microenvironment play critical roles in the reaction kinetics and production rate of electrochemical carbon dioxide reduction reactions (CO₂RR), which steer concerted proton‐electron transfer steps. Inspired by Tillandsia leaves, which efficiently capture H₂O and CO₂ from the air, copper nanosheets with dual‐functional channels are we designed: the superhygroscopic network enables capillary condensation, converting H₂O(g) into H₂O(l) to form H₂O channels that ensure a stable supply of protons, while the CO₂ channels formed by the microporous structure enhance the diffusion of CO₂, thus enriching the carbon source. This synergistic design creates an optimal microenvironment for CO₂ conversion by simultaneously delivering both protons and CO₂ to the reaction interface. Time‐of‐flight secondary‐ion mass spectroscopy (TOF‐SIMS), X‐ray absorption spectroscopy (XAS) and multiphysics simulations further reveal the designed H₂O and CO₂ channels in the microenvironment to boost mass transports. Hence, the Faradaic efficiency (FE) for ethylene reaches up to 96% at ‐200 mA cm⁻² with such localized triple‐phase interfaces, which simultaneously exhibits ultra‐high stability for over 170 h in the membrane electrode assembly (MEA) system. This strategy provides a construction methodology of H₂O and CO₂ channels for improving the selectivity and stability of electrochemical CO₂ upgrades.