Gas-Molecular-Shearing Carbon Vacancy Defect Networks on Ni-Doped Carbon Fibers for High-Efficiency Low-Concentration CO ₂ Enrichment and Electrocatalytic Reduction

Electrocatalytic systems for low-concentration CO2 reduction still face significant challenges in the mass transport and electronic modulation of catalyst active sites. This study developed a gas-molecular shear strategy for constructing nickel single atoms (Ni SAs) and nanocluster (NC)-doped carbon nanofiber catalysts (Ni/TCNFS-10CA; CA = cyanuric acid) featuring carbon vacancy defect engineering and hierarchical porous channels, which created a microenvironment that enhances CO2 adsorption and enrichment. Density functional theory (DFT) and experimental analysis revealed the effects of carbon vacancy defect-engineered Ni NCs on Ni SAs: (1) The introduction of carbon defects can regulate the local electronic structure and pore size, thereby achieving efficient enrichment and adsorption of CO2. (2) Carbon vacancy defects can optimize the key *COOH adsorption and reduce the desorption energy of *CO. The resulting catalyst achieved a near-unity Faradaic efficiency (FE) for CO (FECO ≈100%) over a broad potential window. Notably, it maintained a high FECO of 88.2% under a 20% CO2 atmosphere. The catalyst exhibited durability exceeding 306 h (1102 cycles) in a Zn-CO2 battery and over 80 h (288 cycles) in a Zn-CO2 (20% CO2) battery. This work proposes a high-activity carbon vacancy defect engineering strategy, delivering an innovative approach for efficient ECO2RR and the direct conversion of industrial flue gases.