Pore accessibility matters in CO2 electrolysis: Preventing H2 formation and boosting triple-phase boundary on microtubular gas-diffusion electrodes
Guoliang Chen, Lei Ge, Beibei Ma, Yizhu Kuang, Hesamoddin Rabiee, Fatereh Dorosti, Ashok Kumar Nanjundan, Zhonghua Zhu, Hao Wang
Abstract
The availability of CO 2 near the active sites is crucial for suppressing hydrogen evolution reaction (HER) and improving the kinetics of electrochemical reduction of CO 2 (CO 2 RR) in aqueous electrolytes at high current density. The hollow fiber gas-diffusion electrodes (HFGDEs) configuration can deliver CO 2 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 CO 2 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 CO 2 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 CO 2 bubbling enhancement confirmed the improvement of CO 2 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 CO 2 distribution which can be applied for other gas-phase electrolysis reactions through creating improved triple-phase interfaces and maximizing reaction activity. The pore accessibility maters for gas-diffusion electrodes (GDEs) and the enhanced CO 2 -distributed tubular GDEs were fabricated by optimizing the loading of hydrophobic agents (e.g., PTFE) to improve the pore utilization for CO 2 diffusion. The embedded PTFE can also facilitate the formation of triple-phase boundaries to maximize CO 2 RR to CO formation at high current densities. • A facile strategy was used to boost the pore accessibility of HFGDEs. • The loading of PTFE can mitigate flooding and facilitate triple-phase boundaries. • a ~39% increase in the PCD for CO and 4 times higher stability than P-HFGDE. • This strategy can be used for other gas-phase electrochemical conversion.