Heterogenizing Molecular Electrocatalysts on a Carbon Nanotube-Based Hollow Fiber as Selective and Efficient CO₂ Penetrable Electrodes for High-Current-Density CO Electrosynthesis

While recently developed gas-penetrable electrodes (GPEs) have well-addressed the issues of salt precipitation and flooding faced by the traditional gas diffusion electrodes (GDEs), most developed GPEs are prepared based on the use of high-purity metals with high quantity, which limits their mass production and thus practical application at scale. Herein, we develop carbon-based GPEs by immobilizing (CoPc) molecular electrocatalyst on the surface of a carbon nanotube-interconnected hollow fiber (CoPc/CNTs HF) for the electrosynthesis of CO from the electrocatalytic CO2 reduction reaction (CO2RR) in aqueous solution. Thanks to the improved CO2 mass transfer and the abundance of well-established triphasic reaction interfaces enriched with highly active and selective CoPc electrocatalyst, the as-fabricated CoPc/CNTs HF operating under a GPE configuration demonstrates high performance toward the CO2RR, and it exhibits a maximum partial current density of CO production (jCO) of 153.4 mA cm–2 at −0.93 V vs reversible hydrogen electrode (RHE). Meanwhile, the CO Faradaic efficiency (FECO) of CoPc/CNTs HF is beyond 85% over the whole applied potential range (−0.63 to −0.93 vs RHE) and achieves the highest value of 96.5% at −0.73 V vs RHE. Notably, this CoPc/CNTs HF can maintain stable FECO and jCO for at least 20 h. This work paves a new avenue for the development of carbon-based hybrid GPEs with integrated structure and high performance, which would hold promise for various gas-involved energy-conversion reactions, such as the nitrogen reduction reaction (NRR) and oxygen reduction reaction (ORR).