A research team led by Profs. CHEN Wei and WEI Wei from the Shanghai Advanced Research Institute (SARI) of the Chinese Academy of Sciences reported a novel method that enables efficient CO2 electroreduction to CO by virtue of low-coordination chloride ion adsorption on a silver hollow fiber (Ag HF) electrode. A paper on their work is published in Angewandte Chemie International Edition.
(A) Optical image of the as-fabricated Ag HF tubes. Cross-section SEM images of Ag HF at (B) low and (C) high magnifications. Li et al.
The electrochemical conversion of CO2 into carbon-based fuels and valuable feedstocks by renewable electricity is an attractive strategy for carbon neutrality. CO is the key component of syngas, a mixture of CO and hydrogen that can be directly converted into various value-added chemicals via well-developed industrial processes. Therefore, CO2 electroreduction to CO is one of the most promising routes to obtain cost-competitive products, the researchers said.
However, due to the low solubility and diffusion coefficient of CO2 in aqueous electrolytes, it remains a challenge to possess large current density, high faradaic efficiency and excellent stability for practical applications of CO2 utilization.
Working from the basis of the highly efficient electroreduction CO2 to CO over silver hollow fiber electrodes, the research team further introduced chloride ions into the electrode solution. By means of specific adsorption of chloride ions, the electronic structure of the electrode surface was functionally regulated to inhibit the side reaction of hydrogen evolution.
The low-coordination chloride ion adsorption on a silver hollow fiber electrode reduced CO2 to CO at a stable (>150 h) ampere-level current density (1 A·cm-2) and with a high CO faradaic efficiency of 92.3%.
Electrochemical experiments, operando Raman combined with density functional theory calculations demonstrated that the high concentration Cl- in the electrolyte could be low-coordination adsorbed onto the surface of silver hollow fiber. This not only hinders the occurrence of the hydrogen evolution reaction, but also optimizes the kinetics of CO2 reduction to CO, leading to a better eCO2RR performance, even at the ampere-level current density.
The work provides a new strategy for further developing electrocatalytic CO2 systems with high current density, high selectivity and high stability in CO2 utilization and chlor-alkali industry.
Li, S., Dong, X., Zhao, Y., Mao, J., Chen, W., Chen, A., Song, Y., Li, G., Jiang, Z., Wei, W. and Sun, Y. (2022), “Chloride Ion Adsorption Enables Ampere-Level CO2 Electroreduction over Silver Hollow Fiber.” Angew. Chem. Int. Ed. doi: 10.1002/anie.202210432