Interfacing Dense NiFe@N-Doped Carbon Nanotubes on a Ni Hollow Fiber as a High-Current-Density Gas-Penetrable Electrode for Selective CO2 Electroreduction

Despite proven as effective in overcoming the limitations of low CO2 solubility and inefficient diffusion, traditional gas-diffusion electrodes used in electrocatalytic CO2 reduction reactions (eCO2RR) still face challenges, such as flooding and salt precipitation, and thus exhibit insufficient efficiency and durability at high current densities. Herein, an integrated gas-penetrable electrode (GPE) is developed by interfacially growing dense N-doped carbon nanotubes, embedded with NiFe alloy nanoparticles, on the outer surface of a Ni hollow fiber (NiFe@NCNTs/Ni HF). Thanks to improved mass transfer and the abundance of well-established triphase reaction interfaces, the NiFe@NCNTs/Ni HF GPE exhibits a high CO Faradaic efficiency (FECO) of over 90% across a wide potential range of 240 mV. Furthermore, it displays significantly enhanced partial current density (jCO) of up to 171.7 mA cm–2 at −1.03 V versus reversible hydrogen electrode. Notably, this GPE maintains stable FECO and jCO values for 42 h. This work demonstrates an effective strategy for developing integrated GPEs for efficient eCO2RR by addressing the mass transfer limitation while achieving high efficiency and durability at high current densities.