Marrying Fe nanoclusters with 3D carbon nanofiber aerogels: Triggering fast and robust faradic capacitive deionization

Abstract

Faradic-capacitive deionization (FDI) has emerged promising research branch of capacitive deionization (CDI) to address the crisis in freshwater supply due to its high desalination capacity and unique ion storage mechanism over traditional CDI. However, the ion-storage mechanism of FDI imposes notable limitations on its desalination kinetics, while issues such as volumetric expansion (as well as the damage caused to the composite material’s structure) contribute to poor cycling stability. Herein, we developed a rational material design of Fe nanocluster-impregnated CNFAs (Fe NCs@CNFAs) and further used it as chloride-capturing electrode for FDI. This unique nanostructure not only provides fast surface-driven pseudo capacitance but also establishes a flexible scaffold that effectively protects the Fe NCs from severe morphology changes. As a result, our Fe NCs@CNFAs-based FDI exhibited both ultrahigh desalination capacity (120.38 mg g⁻¹) and fast desalination rate (0.42 mg g⁻¹ s⁻¹), with robust cycling stability (showing only a 15.25 % decrease in desalination capacity after 100 cycles). This study underscores the significance of the problem-driven approach by leveraging soft scaffold-protected ultrasmall nanocluster to induce fast and durable desalination performance.