Carbon Hollow Fiber Penetration Electrode with Unsaturated Ni-N₂ Coordination for Enhanced CO₂ Electroreduction

Hollow fiber gas penetration electrodes with a compact hierarchical pore structure have emerged as promising platforms for CO₂ electroreduction. However, developing carbon hollow fiber electrodes with efficient CO₂ electrocatalytic performance remains unexplored and challenging. Herein, a straightforward strategy is presented to fabricate robust, self-standing carbon hollow fiber electrodes modified with an unsaturated Ni-N₂ coordination structure. This unique hollow fiber electrode configuration effectively enhances the kinetics of CO₂ electro-conversion to CO. Both density functional theory (DFT) calculations and experimental studies reveal that the Ni-N₂ structure significantly boosts electrocatalytic activity for CO₂ reduction by reducing the energy barrier for the key intermediate COOH* formation. Consequently, the electrode with unsaturated Ni-N₂ coordination realizes a high CO Faradaic efficiency (FE) (>90%) as well as a partial current density of 61 mA cm^-2, much superior to those of saturated Ni-N₄ coordination. In particular, this high performance maintains an exceptional durability for over 100 h, outperforming previously reported carbon supporting electrodes featuring Ni-N-C sites. This work opens new avenues for designing advanced carbon electrode structures with enhanced selectivity and activity for CO₂ reduction.