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The quest for cost-efficient electro-active materials exhibiting high specific capacitance is currently a key focus in energy-related research. Owing to their high capacitance values, metal oxides (MOs) are preferably being utilized for energy storage applications as electrode materials in supercapacitors. However, the electrochemical performance of MOs is hindered due to less specific surface area and high tendency towards aggregation. Therefore, tuning in electrochemical activity of MOs is essential. In this framework, NiFe2O4 was prepared using a facile and cost-effective citrate-gel followed by auto-ignition method, and was incorporated with activated carbon contents to tune the electrochemical performance. Formation of inverse spinel structure of NFO and its stability throughout the compositions was examined using X-ray diffraction analysis. Well-dispersed, spherical and porous morphological features were visualized using a field emission scanning electron microscope. The electrochemical analysis was conducted using CH instruments 660 E via freshly prepared 4 M KOH solution. Cyclic voltammetry was carried out at constant potential window of 0.25–0.65 V and different scan rates (0.009–0.08 Vs-1). The pseudo-capacitive behavior was perceived from occurrences of oxidation/reduction peaks. In addition, charge/discharge curves revealed cyclic stability over long range cycles. Specific capacitance, discharge time, energy and power density values were also measured for all the compositions and NFO with 1% activated carbon was found to be the most suitable candidate for use as electrode materials in the present work.

The exceptional high surface area and wide band gap ranges of semiconductor metal oxide nanostructures owe unique chemical, optical and physical properties that have grabbed their utilization for humidity sensing applications. In this framework, cost-effective sensors have been fabricated using a simple spray coating technique. Initially, the sonication was carried out for all the conductive inks such as carbon nanotubes (CNTs), zinc oxide (ZnO) and silver (Ag) nanoparticles (NPs) for 15 min in each case and then sprayed over conducting cellulose polymer substrate. Surface study demonstrated conducting networks of CNTs and cellulose polymer, and layers of ZnO and Ag NPs, as well. The analysis of elemental composition confirmed the required stoichiometric contents. Sensing measurement of CNTs/ZnO/Ag sample showed smaller resistance and enhanced current as compared to CNTs/ZnO sample. Hence, the device showed an efficient activity to sense humidity.

Multiferroic materials have gained research limelight owing to their potential candidature for energy storage applications which are efficiently triggered by their intrinsic magnetoelectric effects. In this context, we present an efficient tri-phase multiferroic composite material, consisting of BiFeO3, CoFe2O4 and Cr2O3 exhibiting exceptional viability for energy storage. The individual constituents were prepared by a citrate-gel based self-ignition route while the composite formation was routed through a ball-milling process. Diffraction patterns revealed the co-existence of three crystalline phases without any impurity within the composites. The morphological features directly influenced the dielectric parameters well in accordance with the Maxwell-Wagner’s bilayer model and the Koop’s phenomenological theory. Likewise, the Nyquist plot architectured a single semicircular arc specifying single relaxation phenomena. The insight of current versus voltage (I-V) curves through the multiferroic tester exposed a gradually declining trend of leakage current against the increasing Cr2O3 phase fractions. The PUND sequences represent high values of switching charge polarization (P*) as paralleled to the un-switching polarization which accompanies leakage current. Magnetic-hysteresis loops exposed a weak ferromagnetic nature of the samples and an increased Cr2O3 phase fractions did not significantly affect the coercivity (Hc) values. The ME-coupling effect was also evident from variation in polarization signals by applied magnetic field. The present study unveils an efficient, scalable and affordable pathway towards the substantial synthesis of tertiary-phase composites exhibiting superb storage properties.

The cost-effective modernized technology, the sol–gel method was employed to synthesize SnO2 nanotubes. Different characterization techniques were carried out including X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), energy-dispersive spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV) measurements; to analyze the prepared nanotubes as a promising electrode material. The tetragonal phase formation in SnO2 was confirmed from the XRD pattern. FESEM provided the nanotube morphology of the as-synthesized sample. EDX analysis profiled the elemental analysis depicting the presence of constitutional elements i.e. Sn, C, and O in the specimen. The valence states of SnO2 nanotubes were perceived by XPS analysis. Additionally, the ongoing electrode reactions were investigated by CV measurements which revealed the anodic/cathodic peaks. High specific capacitance of about 1291.15 F/g was achieved from CV analysis. The superior electrochemical performance was perceived by all the obtained results which make the SnO2 nanotubes a favorable electrode material for futuristic battery applications.

Nanoscale designing of polymer based architectures is essential to enhance the efficiency of energy storage devices for their potential applications in modern day technology. Usually, two phase nanocomposites develop a single type of interface between matrix and filler, causing an increase in dielectric constant and high energy density at the cast of charge discharge efficiency. Herein, we report a three phase (GO/CoFe2O4/PPy) novel class of nanocomposites capable of exhibiting high energy density storage. Three different components of this nanocomposite were synthesized using Hummer’s method, sol-gel auto-combustion technique and polymerization route, separately which were then combined using solution mixing technique in the presence of 0.3 M solution of FeCl3·6H2O. The development of inverse spinel structure of CoFe2O4 and its phase stability was analyzed using X-ray diffraction. Evolution of a variety of nanoarchitectures was confirmed by a field emission scanning electron microscope and its consequences on dielectric and ferroelectric response were probed via precision impedance analyzer and precision multiferroic tester. For the identification of functional groups, Fourier transform infrared spectroscopy was employed and conductive nature was examined using their I–V response curves. Dielectric response of PPy mediated by GO and CFO contents was explained on the basis of Maxwell-Wagner model. The magnetic hysteresis loops were employed and maximum magnetization, remnant magnetization, coercivity and squareness ratio were measured. Using polarization-electric field loops, energy density measurements were carried out which revealed the potential of these nanocomposites for energy storage devices.

Graphene oxide (GO) and polymer based nanocomposites are emerging as a new class of materials having potential for flexible electronic devices and modern day energy storage devices. The traits like high mechanical strength, non-corrosive nature, low weight, being cost-effective, flexible, thermal and electrically insulated have made polymer based nano architectures highly effective for utilizing in energy storage applications. In the present research, the variation in structure, morphology and dielectric response of polypyrrole (PPy) is investigated by adding the nickel ferrite (NiFe2O4) and GO in it. The nano-materials, PPy, NiFe2O4 and GO were prepared by pyrrole’s polymerization, sol‒gel auto-combustion method and modified Hummer’s method, respectively. The solution mixing method was carried out to form GO/NiFe2O4/PPy nanocomposites with different concentrations by slowly mixing the already equipped nanomaterials. X-ray diffraction technique was employed for phase identification of as-prepared nanocomposites. The surface study and elemental composition was examined via field emission scanning electron microscope and energy dispersive X-ray spectroscope, respectively. The dielectric response of these samples was probed using impedance analyzer that was found to be in good agreement with Maxwell-Wagner model and Koop’s Phenomenological theory. Effective contribution of different electro-active regions was investigated from Nyquist plots.