Interfacial confinement of Ag and Bi nanoparticles within N, S-doped carbon for selective and durable chloride capture in asymmetric capacitive deionization

A simple carbothermal reduction–galvanic displacement route enables confined Ag–Bi heterostructures. • Dual Ag/AgCl–Bi/BiOCl conversion delivers 171 .0 mg g −1 Cl⁻ capture. • N,S-doped carbon confinement suppresses Ag dissolution below 0.03 mg L −1 . • Solvation-corrected DFT reveals Ag-enhanced Cl⁻ adsorption and charge transfer. • Stress buffering enables 88% capacity retention during prolonged cycling. Developing high-capacity and durable chloride-storage electrodes is crucial for selective electrochemical desalination. Herein, Ag and Bi nanoparticles were confined within an N, S-doped carbon framework (Ag, Bi@NSCx) through sequential carbothermal reduction and galvanic displacement. By integrating Ag/AgCl and Bi/BiOCl dual-conversion chemistry with conductive carbon confinement, the optimized Ag, Bi@NSC1 electrode enabled an asymmetric capacitive deionization system to deliver a high Cl⁻ capture capacity of 171.0 mg g −1 and a rapid initial removal rate of 40.45 mg g −1 min −1 . The electrode retained approximately 88% of its initial capacity after 50 adsorption–desorption cycles, and the dissolved Ag concentration remained below 0.03 mg L −1 , indicating limited metal leaching during prolonged operation. It also exhibited preferential Cl⁻ capture in multianion solutions and effectively desalinated saline–alkali agricultural drainage water. Solvation-corrected density functional theory calculations revealed that Ag incorporation strengthened Cl⁻ adsorption and induced a favorable charge redistribution across the Ag–Bi interface. Multiphysics simulations further demonstrated that the NSC framework mitigated the stress localization caused by the mismatched volume changes of the Ag/AgCl and Bi/BiOCl phases. The research establishes a dual-conversion and interfacial confinement strategy for achieving selective, high-capacity, and durable chloride capture. Download: Download high-res image (470KB) Download: Download full-size image