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Abundant endeavors have been undertaken to explore high-quality and inexpensive materials for capacitive deionization desalination. However, one major problem is the sluggish adsorption rate and inferior adsorption performance of these materials in practical applications. Herein, nitrogen-doped carbon nanofiber-reinforced hierarchical hollow iron oxide nanorods grown on electrospinning carbon nanofibers (denoted Fe 2 O 3 @CNFs) were rationally designed and synthesized for high-efficiency capacitive deionization. Such composition and distinctive hierarchical porous structure prevent agglomeration of Fe 2 O 3 nanorods, boosting the ionic/electronic transport through the synergistic effect between the Fe 2 O 3 nanorods and N-doped carbon nanofibers. When employed as a cathode for capacitive deionization without adding any polymeric binder or conductive additives, this material exhibits a high adsorption capacity of 114.97 mg/g and a rapid salt adsorption rate (7.79 mg/g min). Moreover, the sodium storage mechanism was revealed through ex situ XRD, EDX mapping and ex situ XPS. Density functional theory (DFT) calculations reveal that the electrons are redistributed at the heterojunction interface, refining the electrochemical activity. This work is anticipated to afford an innovative path for the development of porous transition metal oxide-based fibers with outstanding effectiveness and stability toward environmental research of high-performance capacitive deionization. [Display omitted] • A free-standing hierarchical hollow Fe 2 O 3 @CNFs hybrid electrode was fabricated. • A high electrosorption capacity and a rapid salt adsorption rate were achieved. • The hollow structure alleviates volume expansion and facilitates ion diffusion. • The faradic reaction and electroadsorption coupling removal mechanism was proven. • DFT were implemented to provide in-depth insights into the storage mechanism. [ABSTRACT FROM AUTHOR]

Abstract: A series of hydrous iron oxide samples were prepared by homogeneous precipitation from FeCl3 solution in the presence of SO4 2− ions. Experiments were conducted to study the removal of sulfate ions by varying pH, SO4 2−/Fe3+ molar ratio and the nature of the associated cation. Conventional methods including Infrared Spectroscopy, X-ray Diffraction and Thermal Analyses were used for the characterization of sulfate ions interactions with the hydrous iron surface. The results of macroscopic studies show that the removal of sulfate is highly pH dependent, it is greater at pH range [3–4] and it decreases as the molar ratio enhances. Thermal and IR analyses demonstrate strong interactions of sulfate ions with the hydrous iron oxide. In the pH range studied, the results are consistent with innersphere surface complexes. [Copyright &y& Elsevier]