Carbon-Coated Silver Nanoparticles for Highly Robust Chloride Capture in Electrochemical Desalination and Lithium Recovery

In recent years, electrochemical desalination and resource recovery processes have gained significant attention as means of utilizing waters, wherein the majority of anionic species are chloride ions. There have been research efforts to develop high-performance electrode materials for the chloride uptake. Silver with extremely fast kinetics is an ideal option, but the cost and stability issues are yet to be resolved. Herein, silver nanoparticles with nitrogen-doped carbon (NC) shells are developed for electrochemical Cl⁻ capture in desalination and lithium recovery processes. Starting from commercial Ag powders, nanosized particles are obtained by the chlorination to AgCl, which is followed by the polydopamine coating and thermal annealing. Interestingly, dopamine polymerization can be coupled with the dechlorination of the AgCl, enabling the simultaneous polymeric shell formation and AgCl-to-Ag conversion. This NC-coated Ag nanoparticles (N-Ag@NC) manifest superior capacity and cyclic stability in electrochemical Cl^- capture, when compared with those of Ag particles without NC shells or with a larger (microscale) size. The enhanced performance is attributable to the small particle sizes and the NC shells, which result in a higher Ag utilization and tolerance to the volume changes accompanying the chlorination/dechlorination.