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Highlights: A freestanding MXene-derived defect-rich TiO2@reduced graphene oxides (M-TiO2@rGO) foam electrode was fabricated. M-TiO2@rGO presents fast Na+ storage kinetics due to capacitive contribution. M-TiO2@rGO foam electrode displays a capacity retention of 90.7% after 5000 cycles.Sodium ion batteries and capacitors have demonstrated their potential applications for next-generation low-cost energy storage devices. These devices's rate ability is determined by the fast sodium ion storage behavior in electrode materials. Herein, a defective TiO2@reduced graphene oxide (M-TiO2@rGO) self-supporting foam electrode is constructed via a facile MXene decomposition and graphene oxide self-assembling process. The employment of the MXene parent phase exhibits distinctive advantages, enabling defect engineering, nanoengineering, and fluorine-doped metal oxides. As a result, the M-TiO2@rGO electrode shows a pseudocapacitance-dominated hybrid sodium storage mechanism. The pseudocapacitance-dominated process leads to high capacity, remarkable rate ability, and superior cycling performance. Significantly, an M-TiO2@rGO//Na3V2(PO4)3 sodium full cell and an M-TiO2@rGO//HPAC sodium ion capacitor are fabricated to demonstrate the promising application of M-TiO2@rGO. The sodium ion battery presents a capacity of 177.1 mAh g−1 at 500 mA g−1 and capacity retention of 74% after 200 cycles. The sodium ion capacitor delivers a maximum energy density of 101.2 Wh kg−1 and a maximum power density of 10,103.7 W kg−1. At 1.0 A g−1, it displays an energy retention of 84.7% after 10,000 cycles. [ABSTRACT FROM AUTHOR]

A facile hydrothermal synthetic method, followed by in situ reduction and galvanic replacement processes, is used to prepare PtCo-modified CoO nanosheets (PtCo/CoO NSs) supported on Ni foam. The prepared nanomaterial is used as an electrocatalyst for NaBH oxidation in alkaline solution. The morphology and phase composition of PtCo/CoO NSs are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The catalytic performance of PtCo/CoO NSs is investigated by cyclic voltammetry (CV) and chronoamperometry (CA) in a standard three-electrode system. Current densities of 70 and 850 mA·cm were obtained at-0.4 V for Co/CoO and PtCo/CoO NSs, respectively, in a solution containing 2 mol·L NaOH and 0.2 mol·L NaBH. The use of a noble metal (Pt) greatly enhances the catalytic activity of the transition metal (Co) and CoO. Besides, both Co and CoO exhibit good B-H bond breaking ability (in NaBH), which leads to better electrocatalytic activity and stability of PtCo/CoO NSs in NaBH electrooxidation compared to pure Pt. The results demonstrate that the as-prepared PtCo/CoO NSs can be a promising electrocatalyst for borohydride oxidation. [ABSTRACT FROM AUTHOR]

Cetyltrimethylammonium bromide (CTAB) was used as surfactants to modify the crystallization of β-Ni(OH) via a simple ammonia-evaporation/CTAB-induced method onto nickel foam by using a mixed aqueous solution of nickel nitrate, CTAB, and ammonia. Their structure and surface morphology are characterized by X-ray diffraction and scanning electron microscopy. The SEM images show changes in the microstructure of β-Ni(OH), and the XRD patterns exhibit a much higher relative diffraction intensity of (1 0 0) peaks with the addition of CTAB. The effects of CTAB content on the electrochemical behaviors of β-Ni(OH) are investigated by cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy. The results demonstrate that the modified β-Ni(OH) electrode has better electrochemical performance, such as better reaction reversibility, higher proton diffuse coefficient, higher specific capacity, and better cyclic stability. Importantly, when the CTAB content in the initial solution was 0.03 g, the results show a drastic improvement in the capacitive characteristics of β-Ni(OH) with a specific capacitance increases from 386 to 1,019 F g at a high charging/discharging current density of 6 A g. [ABSTRACT FROM AUTHOR]

In this research, the effect of the different concentrations of NaSnO as the electrolyte additive in 0.7 mol L NaCl solution on the electrochemical performances of the magnesium-8lithium (Mg-8Li) electrode are investigated by methods of potentiodynamic polarization, potentiostatic current-time, electrochemical impedance technique, and scanning electron microscopy (SEM). The corrosion resistance of the Mg-8Li electrode is improved when NaSnO is added into the electrolyte solution. The potentiostatic current-time curves show that the electrochemical behaviors of the Mg-8Li electrode in the electrolyte solution containing 0.20 mmol L NaSnO is the best. The electrochemical impedance spectroscopy results indicate that the polarization resistance of the Mg-8Li electrode decreases in the following order with the concentrations of NaSnO: 0.05 mmol L > 0.00 mmol L > 0.30 mmol L > 0.10 mmol L > 0.20 mmol L. The scanning electron microscopy studies indicate that the electrolyte additive prevents the formation of the dense oxide film on the alloy surface and facilitates the peeling off of the oxidation products. [ABSTRACT FROM AUTHOR]