Browsing by Author "Harish Chandra Verma"

Now showing 1 - 4 of 4

Cation deficiency driven enhancement in electrochemical performance of Sr2-xFeCoO6-δ double perovskite for supercapacitor electrodes
(Elsevier Ltd, 2025) Pramod Rajish Kumar; Arpita Tripathi; Harish Chandra Verma; Aayush Mittal; Bhaskar Bhattacharya; Shail Upadhyay
Properties of perovskite oxides have been tailored to fulfill the requirements of high-capacity and high-power storage devices. This is done by optimizing oxygen vacancy concentration, redox stability, and mixed (ionic and electronic) conductivity. Oxygen intercalation in perovskite oxides is a versatile and robust mechanism for improving the performance of energy storage devices. In this study, a series of non-stoichiometric (Sr-deficient) Sr2-xFeCoO6-δ double perovskite compositions are synthesized using a sol-gel method to increase oxygen vacancy concentration. X-ray diffraction confirmed the formation of a cubic phase with Pm3̅m Space group, stable up to ∼7.5 % Sr deficiency (x = 0.15). Core-level XPS of oxygen revealed that increasing Sr deficiency leads to a higher concentration of adsorbed oxygen species, indicating enhanced oxygen vacancy formation. Sr deficiency leads to a notable increase in specific charge storage capacity, from 15.5 C/g in the stoichiometric sample to 35.3 C/g in the optimized composition. In a symmetric two-electrode configuration, the optimized composition achieved an energy density of 6 Wh/kg, a power density of 780 W/kg, and retained 78 % of its capacity after 5000 cycles. © 2025 Elsevier Ltd
Impact of Current Collectors on the Electrochemical Performance of Pseudocapacitive Material: Sr2FeCoO6
(John Wiley and Sons Inc, 2025) Pramod Kumar; Harish Chandra Verma; Aayush Mittal; Bhaskar Bhattacharya; Shail Upadhyay
This work reports the synthesis of Sr2FeCoO6, double perovskite, via a wet chemical method. X-ray diffraction (XRD) analysis and Rietveld refinement confirmed the successful formation of pure, single-phase perovskite structure with the (Formula presented.) space group. The Raman spectrum showed minor peaks, suggesting structural distortions likely caused by defects. Transmission electron microscopy (TEM) revealed irregularly shaped polycrystalline particles, while Brunauer–Emmett–Teller (BET) analysis indicated an average surface area of 3.01 m2/g and a pore diameter of 37.8 nm. Current collectors, namely, carbon Toray paper, carbon cloth, nickel foam, and nickel strip, were selected to evaluate the electrochemical properties of Sr2FeCoO6. The morphology of the current collectors was captured using a scanning electron microscope (SEM). The electrochemical performance of bare and loaded (with Sr2FeCoO6) current collectors was assessed under similar measurement conditions. The high specific capacitance of the sample is observed over the carbon cloth and nickel foam to be 105.7 and 93.3 F/g, respectively, while bare carbon cloth shows very high capacitance. By comparing the performance of different current collectors, we have identified the key factors influencing the material's performance. This study will enhance our understanding of its potential applications in energy storage and other pertinent areas. © 2025 John Wiley & Sons Ltd.
Investigation of La2FeO4-rGO nanocomposite electrode material for symmetric and asymmetric supercapacitor
(Elsevier Ltd, 2025) Harish Chandra Verma; Pramod Kumar; Satyendra Kumar Satyarthi; Bhaskar Bhattacharya; Akhilesh Kumar Singh; Shail Upadhyay
Ruddlesden-Popper (RP) oxides, represented by the general formula of An+1BnO3n+1, are emerging as promising electrode materials for supercapacitors (SCs) electrodes due to their stable crystal structure, rich oxygen vacancies, and good reversible redox behavior. In this study, La2FeO4 and 2D reduced graphene oxide (rGO) were synthesized via a solid-state reaction method and Modified Hummer method, respectively. Nanocomposites of La2FeO4/rGO in a varying weight ratios (0:1, 1:0, 1:1, 1:2, 1:3, 1:4, and 1:5 wt %) were subsequently synthesized through a hydrothermal method. The synthesized La2FeO4 and optimized La2FeO4-rGO (1:4) nanocomposite were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), high-resolution SEM (HR-SEM), high-resolution transmission electron spectroscopy (HR-TEM) techniques and Brunauer-Emmett-Teller (BET) techniques. Electrochemical measurement evaluated in a 3 M KOH electrolyte solution revealing the remarkable performance of the composites. Fabricated symmetric supercapacitors (SSCs) based on La2FeO4-rGO (1:4)/La2FeO4-rGO (1:4) have demonstrated the gravimetric capacitance values of 633, 298, 226, 139, and 72 F/g at current densities of 1, 2, 3, 5, and 10 A/g, respectively. Similarly, an asymmetric supercapacitor (ASC) configuration La2FeO4-rGO (1:4)/rGO have shown capacitance 197, 160, 108, 89, and 58 F/g values at the same current densities. SSCs and ASCs assemblies have exhibited outstanding capacitance retention (91.1 % for SSCs, 99.9 % for ASCs) and high coulombic efficiency (99.5 % for SSCs, and 74 % for ASCs). Additionally, these devices displayed a maximum specific power density (7.8 KW/kg for SSCs, and 20 KW/kg for ASCs) and a maximum specific energies (148 Wh/kg for SSCs, and 70 Wh/kg for ASCs). © 2025
Sintering temperature controlled giant dielectric, Ge - doped CaCu3Ti4O12 ceramics for electrical energy storage, optoelectronics and super capacitor applications
(Elsevier Ltd, 2025) Satyendra Kumar Satyarthi; Harish Chandra Verma; Vishwa Pratap Singh; V. Punith Kumar; Nitin K. Puri; Ramanand Rai; Ramam V.S. Koduri; Shail Upadhyaya; Akhilesh Kumar Singh
Ge-doped CaCu3Ti4O12 ceramics with composition CaCu3Ti3.9Ge0.1O12 were synthesized using a wet chemical method and sintered at different temperatures to study their properties. X-ray diffraction confirmed single-phase cubic structure for all sintering temperatures, with improved crystallinity observed at higher sintering temperatures. Morphological analysis showed 1050°C as the optimal sintering temperature, balancing grain growth without excessive liquid phase. Optical studies revealed the lowest band gap of 2.16 eV for sample sintered at 1050°C, along with strong photoluminescence dominated by cyan emission at 513.5 nm. Ge doping allowed tunable emissions from 470 to 620 nm with an effective half lifetime of 1.30 ns, which can be very useful for optoelectronics. Dielectric measurements peaked for sample sintered at 1050°C, showing enhanced polarization and charge mobility, along with increased grain boundary resistance and non-Debye relaxation, indicating improved insulation and internal barrier layer capacitor behavior. Electrochemical tests demonstrated excellent pseudocapacitive performance with over 90 % capacitance retention after many cycles. Overall, CaCu3Ti3.9Ge0.1O12 is a promising multifunctional material for hybrid (Electrical and Electro-chemical) energy storage and optoelectronic applications. © 2025 Elsevier B.V.