Reconstructed Bismuth Nanoparticles@Porous Carbon Nanorod with Modulated Bismuth-Oxygen Structure and Active Sites for Highly Efficient Electrochemical Dechlorination

Abstract

Bismuth (Bi)-based electrodes hold great potential for chloride ion (Cl^-) capture and storage in terms of their high theoretical capacity and excellent selectivity, yet they still suffer from sluggish kinetics, severely impeding their application. Herein, to address this issue, a promising metal-organic framework (MOF)-confined redox-mediated reconstruction strategy is conducted to synthesize the reconstructed bismuth nanoparticles@porous carbon nanorod (rBi@C). It features the modulated bismuth-oxygen (Bi-O) structure and active sites for enhanced rate of Cl^- removal. In addition, during the redox process, the confinement effect of MOF-derived carbon prevents Bi nanoparticles from enlarging in size and aggregation. As a result, the rBi@C electrode exhibits impressive deionization capabilities, with an excellent capacity of 72.61 ± 1.31 mg-Cl^- g^-1 and a remarkable time-averaged deionization rate of 8.58 ± 0.73 mg-Cl^- g^-1 min^-1, while maintaining outstanding cycling stability. The density functional theory and various characterizations reveal that increased Bi-O structure and lower-coordinated Bi-Bi sites lower the adsorption energy of Cl^- and reduce the activation energy barrier for Cl^- capture, thereby promoting deionization activity and facilitating faster rate. This work provides an effective strategy based on modulating the Bi-O structure through reconstruction to improve the kinetics of Bi-based electrodes for Cl^- removal, thus promoting the application of electrochemical deionization.