Theoretical and experimental investigations of BiOCl for electrochemical adsorption of cesium ions

BiOCl was found to have excellent electrochemical adsorption properties for cesium ions (Cs+) in electrochemically switched ion exchange (ESIX). In this work, BiOCl nanosheets were synthesized by a hydrothermal method and used for electrochemical adsorption of Cs+. The experimental results showed that BiOCl exhibited higher electrochemical adsorption selectivity for Cs+ than Li+ and Na+. Quantum chemical calculations based on density functional theory (DFT) were first performed to compare the adsorption and migration mechanisms of three ions Li+, Na+, and Cs+ in BiOCl crystals. The calculation results revealed that the excellent electrochemical adsorption performance of BiOCl for Cs+ is due to the interaction of embedded Cs with Cl and Bi in BiOCl crystals. This makes it have a higher adsorption energy and a lower ion migration energy barrier due to the balance of interaction forces. In this work experimental and theoretical calculations were used to systematically analyze the adsorption and migration of three ions in BiOCl, which has important guiding significance for the design of highly-efficient electroactive materials for electrochemical adsorption of Cs+.