High-efficiency electrochemical air capture enabled by thiadiazole redox carrier with tunable gas-selective channels.

Abstract

Electrochemical direct air CO₂ capture (eDAC) using redox carriers enables sustainable decarbonization but suffers efficiency losses from O₂-induced side reactions such as oxygen reduction and carrier oxidation. We introduce a composite electrode BPT-GPL by integrating 2,5-bis(4-pyridyl)-1,3,4-thiadiazole (BPT) with ether oxygen (-O-) enriched gas permeation layer (GPL), forming a tunable gas transport channel that facilitates CO₂ diffusion while limiting O₂ penetration. Under atmospheric conditions (~400 ppm CO₂, 21% O₂), the BPT - GPL system demonstrates high eDAC capacity of 3.3 ± 0.2 mmol g^-1_BPT across 48 cycles with negligible redox carrier degradation. The thiadiazole ring-based BPT molecules increase electron delocalization, exhibiting moderate CO₂ binding strength and high O₂ tolerance. Moreover, GPL allows CO₂ diffusion and suppresses O₂ permeation creating low-O₂ microenvironment that inhibits side reactions and maintains cycling stability. Molecular dynamics (MD) simulations suggest that ether oxygen's stronger affinity for CO₂ than O₂ increases CO₂ solubility within GPL, resulting in preferential CO₂ permeation. The BPT - GPL system favors CO₂ delivery and restricts O₂ transport, enabling efficient eDAC and highlighting the potential for practical implementation.