Pore accessibility matters in CO2 electrolysis: preventing H2 formation and boosting triple-phase boundary on microtubular gas-diffusion electrodes

Pore accessibility matters in CO2 electrolysis: preventing H2 formation and boosting triple-phase boundary on microtubular gas-diffusion electrodes

The availability of CO2 near the active sites is crucial for suppressing hydrogen evolution reaction (HER) and improving the kinetics of electrochemical reduction of CO2 (CO2RR) in aqueous electrolytes at high current density. The hollow fiber gas-diffusion electrodes (HFGDEs) configuration can deliver CO2 continuously to catalyst/electrolyte interfaces without requiring a separate gas chamber, contrasting with planar gas-diffusion electrodes (GDEs). However, the relatively inhomogeneous pore geometry on the surface of HFGDEs leads to poor CO2 distribution, resulting in an increasing number of flooded pores and parasitic HER, especially at high current densities. This work presents a facile strategy to enhance CO2 distribution and optimize triple-phase boundary formation by manipulating the surface wettability of HFGDEs. The infiltration and melting of hydrophobic agents (e.g., polytetrafluoroethylene (PTFE)) have been carried out on the Zn nanosheet-deposited Cu hollow fiber. The fluorescent residue area (water surface coverage) with a ∼66.7 % decrease and the observation of CO2 bubbling enhancement confirmed the improvement of CO2 distribution on HFGDE, and the resulting HFGDE achieved around ∼39 % increase in terms of industrial-scale CO partial current density and 4 times higher stability compared to the pristine HFGDE. This research highlights the use of HFGDEs to achieve gas flow-through, further combining with a versatile strategy to enhance CO2 distribution which can be applied for other gas-phase electrolysis reactions through creating improved triple-phase interfaces and maximizing reaction activity.