Technologies for the effective and energy efficient removal of salt from saline media for advanced water remediation are in high demand. Capacitive deionization using carbon electrodes is limited to highly diluted salt water. Our work demonstrates the high desalination performance of the silver/silver chloride conversion reaction by a chloride ion rocking-chair desalination mechanism. Silver nanoparticles are used as positive electrodes while their chlorination into AgCl particles produces the negative electrode in such a combination that enables a very low cell voltage of only Δ200 mV. We used a chloride-ion desalination cell with two flow channels separated by a polymeric cation exchange membrane. The optimized electrode paring between Ag and AgCl achieves a low energy consumption of 2.5 kT per ion when performing treatment with highly saline feed (600 mM NaCl). The cell affords a stable desalination capacity of 115 mg g⁻¹ at a charge efficiency of 98%. This performance aligns with a charge capacity of 110 mA h g⁻¹.

In recent years, electrochemical water desalination with battery electrode materials has emerged as a promising solution for energy-efficient salt-water desalination. Here, we report the promising desalination performance of a hydrothermally synthesized vanadyl phosphate material (mixed phases of sodium vanadyl phosphate dehydrate and vanadyl hydrogen phosphate hemihydrate) as a new electrode material. We observed robust stability of the synthesized electrode material over 280 cycles during desalination operation for 100 mM NaCl feedwater which was continuously flowing along the electrode material. During the first 100 cycles, the charge storage capacity was enhanced by 47%. This enhancement seems to be caused by a continuous conversion to vanadyl phosphate monohydrate from initial phases according to the post-mortem analysis by X-ray diffraction and infrared spectroscopy. The maximum sodium uptake capacity of the vanadyl phosphate electrode was 24.3 mg g⁻¹ with charge efficiency of around 85%. We found no detectable level of contamination by phosphor nor vanadium from the treated water stream indicating that our synthesized electrode is also environmentally safe for water desalination applications.

A sulfur–1,3-diisopropenylbenzene copolymer was synthesized by ring-opening radical polymerization and hybridized with carbon onions at different loading levels. The carbon onion mixing was assisted by shear in a two-roll mill to capitalize on the softened state of the copolymer. The sulfur copolymer and the hybrids were thoroughly characterized in structure and chemical composition, and finally tested by electrochemical benchmarking. An enhancement of specific capacity was observed over 140 cycles at higher content of carbon onions in the hybrid electrodes. The copolymer hybrids demonstrate a maximum initial specific capacity of 1150 mA h g_sulfur ⁻¹ (850 mA h g_electrode ⁻¹) and a low decay of capacity to reach 790 mA h g_sulfur ⁻¹ (585 mA h g_electrode ⁻¹) after 140 charge/discharge cycles. All carbon onion/sulfur copolymer hybrid electrodes yielded high chemical stability, stable electrochemical performance superior to conventional melt-infiltrated reference samples having similar sulfur and carbon onion content. The amount of carbon onions embedded in the sulfur copolymer has a strong influence on the specific capacity, as they effectively stabilize the sulfur copolymer and sterically hinder the recombination of sulfur species to the S₈ configuration.