Unveiling the role of silicon in boosting electrochemical carbon dioxide reduction via carbon nanotubes@bismuth silicates

Electrochemical CO 2 reduction reaction (CO 2 RR) is one of the most attractive measures to achieve the carbon neutral goal by converting CO 2 into high-value chemicals such as formate. Si in Bi silicates is promising to enhance CO 2 adsorption and activation due to its strong oxygenophilicity. Whereas, its role in boosting CO 2 RR via the cheap Bi-based catalysts is still not clear. Herein, we design CNT@Bi silicates catalyst, demonstrating the highest FE HCOOH of 96.3 % at −0.9 V vs . reversible hydrogen electrode with good stability. Through X-ray photoelectron spectroscopy (XPS), in-situ Attenuated Total Reflectance-Fourier Transform Infrared ( In-situ ATR-SEIRAS) experiments, and Density Functional Theory (DFT) calculations, the role of Si in Bi silicates was unveiled: tuning the electronic structure of Bi, weakening the Bi-O bond, and strengthening electron transfer from Bi to CO 2 , thereby promoting the generation of CO 2 * − and *OCHO intermediates. Additionally, carbon nanotubes (CNTs) promote not only the conductivity but also the generation of abundant oxygen vacancies in CNT@Bi silicates evidenced by the electron transfer from CNT to Bi silicates from XPS results. Further, the CNT@Bi silicates endows it with the highest electrochemical activation area. These findings suggest the effectiveness of Si in Bi silicates and structure tuning to design highly selective CO 2 RR catalyst for HCOOH production.