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Three-dimensional (3D) printing offers a unique approach to fabricating free-standing and complex structured electrodes for high-performance micro-supercapacitors (MSCs). Among the different 3D-printing techniques, fused deposition modeling (FDM) is a promising technique for upscaling due to its low price and maturity in industry. Herein, a conductive carbon black-based 3D-printable filament is designed to be used as a free-standing electrode after FDM printing, solvent activation, and MXene coating. The MXene layers could provide higher capacitances due to the pseudocapacitive charge storage mechanism and high metallic conductivity. In a three-electrode test system, the MXene decorated 3D-printed electrode (MXene@PTC-12 h) shows a capacitance of 30.2 mF cm−2 at a current density of 0.1 mA cm−2. With polyvinyl alcohol (PVA)/H2SO4 gel electrolyte, the MSCs based on the 3D printed electrodes provide a specific capacitance of 20.8 mF cm−2 at a current density of 0.1 mA cm−2 and a stable cycle life with 95% capacitance retention after 10 000 cycles. The method in this work offers a new way to prepare customized free-standing electrodes for high-performance energy storage devices. [ABSTRACT FROM AUTHOR]

Gamma irradiation-based synthesis and modification of nanomaterials has emerged as a versatile technique to increase the electrochemically active sites for catalytic reactions. Ionizing radiation has a tremendous effect on the optical, electrical, microstructural, and physicomechanical properties of nanomaterials. By controlling the irradiation parameters such as the absorbed dose rate and the total absorbed dose, tunable synthesis and surface modifications can be achieved. Herein, the gamma irradiation technique was used to modify the Ti3C2Tx MXene and the effect on the electrochemical performance of gamma-irradiated Ti3C2Tx (γ-Ti3C2Tx) for the hydrogen evolution reaction (HER) and supercapacitor applications was studied. The irradiated structure was characterized using X-ray diffraction and scanning electron microscopy, which confirmed the formation of γ-Ti3C2Tx MXene. The electrochemical properties were examined by cyclic voltammetry, galvanostatic charge–discharge, and linear sweep voltammetry. The γ-Ti3C2Tx exhibits a specific capacitance of 169 F g−1 at 10 A g−1, with 87% capacitance retention after 5000 charge/discharge cycles. Furthermore, the γ-Ti3C2Tx-300 electrocatalyst shows an overpotential of 478 mV with a Tafel slope of 157 mV dec−1. The enhanced electrochemical properties of the gamma-irradiated MXene electrodes were attributed to quick diffusion pathways enabled by increased d-spacing upon irradiation. [ABSTRACT FROM AUTHOR]

An essential challenge faced by pseudocapacitive electrode materials is insufficient charge storage capability with high intrinsic electrical resistance and structural instability. With an exponential increase in the demand for a pollutant-free environment, ternary metal compounds are being extensively explored as an attractive solution to these problems. Herein, we have addressed a solution to the above-listed issues by synthesizing novel and binder-free NiMnCo layered double hydroxide (NiMnCo-LDH) nanosheets on Fe-substituted NiCo2O4 (FexNi1−xCo2O4) nanorods supported on nickel foam via a facile hydrothermal method followed by chemical bath deposition. The highly defined and well-distributed porous Fe-substituted NiCo2O4 nanorod structure integrated with the ternary NiMnCo-LDH nanosheets provide ultra-fast kinetics of charge transfer, increased charge storage capacity, and high structural stability. The nanocomposite electrode delivers a high specific capacity of 281 mAh/g at a scan rate of 5 mV/s (265 mAh/g at 1 A/g) with a capacitance retention of 92% after 5000 cycles at 2 A/g. The effect of Fe in NiCo2O4 is further validated by performing density-functional theory (DFT) calculations to obtain atomic insights on electrical conductivity using the density of states (DOS) and band structures. Finally, a symmetric supercapacitor based on FexNi1−xCo2O4@NiMnCo LDH was assembled which delivered an impressive energy density of 105 Wh/kg and a power density of 1112 W/kg, proving FexNi1−xCo2O4@NiMnCo-LDH as an electrode material to be used for applications of energy storage. [ABSTRACT FROM AUTHOR]

The aim of the present work was to synthesize magnetite (Fe3O4) nano hollow spheres (NHS) via simple, one-pot, template-free, hydrothermal method. The structural, morphological, and surface analysis of Fe3O4 NHS were studied by scanning electron microscopy (SEM), x-ray diffraction technique (XRD), Fourier transform infrared spectroscopy FTIR and burner-Emmett-teller (BET). The as obtained magnetic (Fe3O4) NHS were used as an adsorbent for treating industrial trinitrotoluene (TNT) wastewater to reduce its Chemical Oxygen Demand (COD) values. Adsorption capacity (Qe) of the NHS obtained is 70 mg/g, confirming the attractive forces present between adsorbent (Fe3O4 NHS) and adsorbate (TNT wastewater). COD value of TNT wastewater was reduced to >92% in 2 h at room temperature. The adsorption capacity of Fe3O4 NHS was observed as a function of time, initial concentration, pH, and temperature. The applied Fe3O4 NHS was recovered for reuse by simply manipulating its magnetic properties with slight shift in pH of the solution. A modest decrease in Qe (5.0–15.1%) was observed after each cycle. The novel Fe3O4 NHS could be an excellent candidate for treating wastewater generated by the intermediate processes during cyclonite, cyclotetramethylene-tetranitramine (HMX), nitroglycerin (NG) production and other various environmental pollutants/species. [ABSTRACT FROM AUTHOR]