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Electrode materials comprising SnO2 quantum dots embedded within ZnO hexagonal prisms were successfully synthesized for building cost-effective energy-storage devices. Extensive structural and functional characterizations were performed to assess the electrochemical performance of the electrodes. SEM–EDS results confirm a uniform distribution of SnO2 quantum dots across ZnO. The integration of SnO2 quantum dots with ZnO hexagonal prisms markedly improved the electrochemical behavior. The analysis of electrode functionality conducted in a 3 M KOH electrolyte revealed specific capacitances of 949.26 and 700.68 F g⁻1 for SnO2@ZnO and ZnO electrodes, respectively, under a current density of 2 A g⁻1. After undergoing 5,000 cycles at a current density of 15 A g⁻1, the SnO2@ZnO and ZnO electrodes displayed impressive cycling stability, maintaining specific capacitance retention rates of 89.9 and 92.2%, respectively. Additionally, a symmetric supercapacitor (SSC) device constructed using the SnO2@ZnO electrode showcased exceptional performance, exhibiting a specific capacitance of 83 F g⁻1 at 1.2 A g⁻1. Impressive power and energy densities were achieved by the device, with values reaching 2,808 and 70.2 W kg⁻1, respectively. Notably, the SnO2@ZnO SSC device maintained a capacity preservation of 75% throughout 5,000 galvanostatic charge–discharge sequences. The outcomes highlight the potential of SnO2@ZnO hexagonal prisms as candidates for energy-storage applications, offering scalability and cost-effectiveness. The proposed approach enhances the electrochemical performance while ensuring affordability, facilitating the creation of effective and financially feasible energy storage solutions.

Herein, this report uses Co3O4 nanoneedles to decorate Mo-Co3O4 nanosheets over Ni foam, which were fabricated by the hydrothermal route, in order to create a supercapacitor material which is compared with its counterparts. The surface morphology of the developed material was investigated through scanning electron microscopy and the structural properties were evaluated using XRD. The charging storage activities of the electrode materials were evaluated mainly by cyclic voltammetry and galvanostatic charge-discharge investigations. In comparison to binary metal oxides, the specific capacities for the composite Co3O4@Mo-Co3O4 nanosheets and Co3O4 nano-needles were calculated to be 814, and 615 C g−1 at a current density of 1 A g−1, respectively. The electrode of the composite Co3O4@Mo-Co3O4 nanosheets displayed superior stability during 4000 cycles, with a capacity of around 90%. The asymmetric Co3O4@Mo-Co3O4//AC device achieved a maximum specific energy of 51.35 Wh Kg−1 and power density of 790 W kg−1. The Co3O4@Mo-Co3O4//AC device capacity decreased by only 12.1% after 4000 long GCD cycles, which is considerably higher than that of similar electrodes. All these results reveal that the Co3O4@Mo-Co3O4 nanocomposite is a very promising electrode material and a stabled supercapacitor. [ABSTRACT FROM AUTHOR]

The influence of Ag doping on the SnO2 sensor operating at room temperature is reported in this work. The SnO2 and Ag-doped SnO2 films are deposited by the nebulizer spray pyrolysis method with different Ag (1, 2, 3, and 4 wt%) concentrations. The characterization of doped thin films was done using multiple advanced techniques to understand their crystallization, morphology, optical and electrical properties to find the optimized Ag concentration on the SnO2 surface. It was found that the doping of different concentrations into the SnO2 lattice increases the preferential orientation of the peak along (211) plane up to 3wt% Ag and starts decreasing at 4 wt%. The estimated crystallite size of the 3wt% Ag-doped SnO2 thin films shows larger value of 98 nm with improved thickness and decreased strain. The morphologies of all the prepared thin films exhibits small leafy flakes structure with change in the particle size and improved agglomeration with increased Ag concentration. The optical studies showed better transparency in the visible and near-IR regions with decreased transmittance and increase in bandgap with increasing Ag concentration in SnO2. The PL results suggest that the 3wt% Ag-doped SnO2 has high-intensity emission peaks over the visible regions indicating the presence of more oxygen vacancies which acts as recombination centers to trap large amount of target gas. Finally, the gas sensing properties of the samples at different concentration of ammonia gas (i.e., 50, 100, 150, 200, and 250 ppm) are studied, which revealed that the 3wt% Ag-doped SnO2 showed better sensitivity/response of 120% with maximum response and recovery times of 32 and 17 s at 250 ppm of ammonia gas. Thus, the undoped SnO2 has been optimized with different doping amounts of Ag ions to obtain the best ammonia sensor. [ABSTRACT FROM AUTHOR]