Hollow fiber gas-diffusion electrodes with tailored crystal facets for tuning syngas production in electrochemical CO2 reduction

Abstract

Electrochemical reduction of CO2 (CO2RR) in aqueous electrolytes not only relies on advanced gas diffusion electrodes (GDEs) to improve CO2 mass transportation but also efficient electrocatalysts to produce specific products. Herein, to produce syngas (CO and H2 mixture), a facet-orientated zinc nanosheet catalyst was electrodeposited on the Cu hollow fiber GDE via a controllable facile surfactant-assisted method. The introduction of cationic surfactant cetyl trimethyl ammonium bromide (CTAB) could manipulate the nucleation and crystal growth of zinc ions around the GDE during the electrodeposition process, leading to controlled changes in the surface free energy and tuned zinc crystal growth orientation. Consequently, the ZncNS-HF with the largest ratio of Zn (101)/Zn (002), resulted in a high current density of 73.3 mA/cm2 and a high syngas production rate of 1328.6 µmol/h∙cm2 at applied potential −1.3 V (vs. RHE). This comes from the hierarchical structure of HFGDE, which provides sufficient CO2 reaching the catalyst/electrolyte interface, and the well-connected zinc nanosheets contribute to a significant number of active sites for CO2RR. This is the first time to configure flow-through or gas-penetrated HFGDEs with zinc crystal facets controlled nanosheet catalysts for syngas production. This research demonstrates the high potential of nanoengineering catalysts for HFGDEs to achieve high production rates of syngas.