Electrodeposited Na-Birnessite on Carbon Cloth as Positive Electrode for Capacitive Deionization

Capacitive Deionization (CDI) based on traditional activated carbon (AC) electrodes faces some important intrinsic hurdles, such as the co-ion expulsion phenomenon and unwanted faradaic reactions, harming efficiency, operational stability, and electrode lifetime. The incorporation of ion-exchange membranes (IEM) in CDI, as free-standing films applied onto the electrodes, was shown to be an effective solution to improve charge efficiency and has led in fact to the commercialization of MCDI (membrane-CDI). An alternative way to improve CDI performance is the use of ion insertion materials, such as metal oxides and layered double hydroxides. In this work, we examine the performance of sodium-birnessite electrodeposited on commercial carbon cloth (CC) as the positive electrode of a flowby CDI cell, coupled to an ordinary AC / AEM stack as the negative electrode

Evaluation of Co-Ion Desorption and Faradaic Losses in Capacitive Deionization

The efficiency of Capacitive Deionization (CDI) is largely determined by the charge loss associated with two distinct parasitic processes, namely, co-ion expulsion and faradaic reactions. There is wide agreement that the first factor dominates the inefficiency of CDI; however, the evaluation of the relative incidence of co-ion repulsion on CDI inefficiency remains somewhat elusive. In this work, in the assumption of relatively small ohmic losses, we propose a simple model to quantify charge losses due to either of these processes in CDI cells, disregarding ohmic losses

Boosting the Power of Na0.44MnO2: Unlocking Its Potential for Aqueous Sodium-Ion Storage through Nanostructuring and Hybridization

We report an effective processing route, combining nanostructure formation and hybridization, to improve the rate performance of the tunnel-structure sodium manganese oxide Na0.44MnO2 (NMO) as a cathode material for aqueous sodium ion storage. We use hydrothermal synthesis to prepare an NMO/CNF (Carbon NanoFiber) hybrid, consisting of uniform oxide nanowires with an average width of 70 nm and length in the range of several tenths of µm. The highly dispersed CNFs impart high conductivity to the NMO/CNF electrode, allowing high-rate performance at a C-rate of up to 20 C, with a delivered capacity of more than half the theoretical value in a 1 M Na2SO4 electrolyte. Moreover, the NMO/CNF hybrid shows good electrochemical stability under several hundred cycles at a high C-rate. However, the NMO nanowire electrodes reveal a lower-than-expected capacity, probably as a result of the tendency of nanowires to form bundles, which prevents direct contact with conductive fibers and induce the under-utilization of active material. With this study, we demonstrate a strong improvement of the otherwise inherently low-rate performance of NMO through oxide nanostructuring and hybridization with carbon fibers, paving the way for further research on NMO-based materials for aqueous sodium ion storage

Morphology and Intramolecular Interactions in P(VDF-TrFE) Electrospun Nanofibers Doped with Disperse Orange 3 Dye: A Joint Infrared Spectroscopy and Electron Microscopy Study

[Image: see text] In this study, we describe a host–guest system consisting of a push–pull dye, the 4-amino-4′-nitroazobenzene (Disperse Orange 3, DO3), mixed with the copolymer poly(vinylidene fluoride-co-trifluoroethylene) [P(VDF-TrFE)] as a potential candidate for nonlinear optics (NLO) applications. We developed electrospun nanofibers of the polymer/dye blend, showing a highly anisotropic molecular structure, where DO3 molecules are mostly oriented parallel to the polymer chain, running in the fiber axis direction. The technique opens a way for obtaining non-centrosymmetric ordering of the NLO chromophore without requiring further poling. The supramolecular architecture is deeply investigated through infrared vibrational spectroscopy, which allows detecting a new phase involving DO3 molecules linked together by strong directional H-bonds. Electron microscopies highlight peculiar nanofiber morphologies with a preferred localization of DO3 at the surface layers

Boosting the Power of Na_0.44MnO₂: Unlocking Its Potential for Aqueous Sodium-Ion Storage through Nanostructuring and Hybridization

We report an effective processing route, combining nanostructure formation and hybridization, to improve the rate performance of the tunnel-structure sodium manganese oxide Na0.44MnO2 (NMO) as a cathode material for aqueous sodium ion storage. We use hydrothermal synthesis to prepare an NMO/CNF (Carbon NanoFiber) hybrid, consisting of uniform oxide nanowires with an average width of 70 nm and length in the range of several tenths of µm. The highly dispersed CNFs impart high conductivity to the NMO/CNF electrode, allowing high-rate performance at a C-rate of up to 20 C, with a delivered capacity of more than half the theoretical value in a 1 M Na2SO4 electrolyte. Moreover, the NMO/CNF hybrid shows good electrochemical stability under several hundred cycles at a high C-rate. However, the NMO nanowire electrodes reveal a lower-than-expected capacity, probably as a result of the tendency of nanowires to form bundles, which prevents direct contact with conductive fibers and induce the under-utilization of active material. With this study, we demonstrate a strong improvement of the otherwise inherently low-rate performance of NMO through oxide nanostructuring and hybridization with carbon fibers, paving the way for further research on NMO-based materials for aqueous sodium ion storage