Bimetallic copper-bismuth microtubular electrodes with tunable interfaces for efficient electrochemical reduction of CO2 to formate
Beibei Ma, Hesamoddin Rabiee, Guoliang Chen, Yizhu Kuang, Tianjiu Zhu, Penghui Yan, Lei Ge, Zhonghua Zhu
Abstract
Electrochemical reduction of CO 2 (CO 2 RR) offers a sustainable route for CO 2 utilization, with emerging carbon-free gas-diffusion electrodes (GDEs) mitigating the flooding issues that limit its performance. Metal-based microtubular (hollow fiber) GDEs (HFGDEs) are particularly promising due to enhanced mass transfer by gas flow-through feed, superior charge transfer and mechanical strength. Copper-based GDEs are efficient for CO 2 RR but often lack selectivity. Introducing bimetallic interfaces on GDE surfaces is an effective strategy to modulate CO 2 RR pathways. Herein, CuBi bimetallic HFGDEs were fabricated for CO 2 RR through a facile premixing approach. The CuBi HFGDE with 10 wt% Bi incorporation (CuBi-10) created abundant Cu/Bi interfaces at the triple-phase boundaries, while preserving the CO 2 accessibility of the HFGDEs. Operating CuBi HFGDE in flow-through GDE mode ensured sufficient CO 2 supply, effectively suppressing HER and enhancing formate selectivity. CuBi-10 achieved over 90 % Faradaic efficiency (FE) for formate across a low potential window (−0.9 to −1.1 V vs. RHE), significantly outperforming monometallic Cu HFGDE (formate FE < 20 % at all applied potentials). The superior formate partial current density of CuBi-10 over Cu HFGDE (more than 5 times higher at −1.1 V vs. RHE) was due to the increased active sites and lower charge transfer resistance. In-situ Raman analysis revealed that the Cu/Bi interface effectively suppresses HER and promotes the ⁎ OCHO pathway during CO 2 -to-formate conversion. This work presents the promise toward designing metal-based HFGDEs with bimetallic interfaces at triple-phase boundaries for selective CO 2 RR to formate. Engineering bimetallic Cu/Bi interface on microtubular gas-diffusion electrodes for selective CO 2 RR to formate. • Tuning Cu/Bi interfaces at triple-phase boundaries for formate production • Flow-through HFGDEs provide sufficient CO 2 supply and effectively suppress HER. • Formate selectivity over 90 % across a low potential range (−0.9 to −1.1 V vs. RHE) • This strategy enables HFGDE design with bimetallic interfaces for selective CO 2 RR.