Pseudocapacitive Behavior of (Fe, Cu) Based Co3O4 as High-Performance Electrode Materials for Solid-State Stiff and Flexible Supercapacitors Samatha K, Raghavendra Sagar Energy Technology, 2025 Detailed investigation into the electrochemical behavior of Fe‐ and Cu‐substituted Co3O4, prepared via a hydrothermal technique in the form of FeCo2O4 and CuCo2O4 at 150 °C, is reported in this study. X‐ray diffraction analyses of all three compositions confirmed the formation of highly crystalline, single‐phase spinels with cubic symmetry. Scanning electron microscopy images revealed distinct morphologies with spherical, flower‐like, and clustered grains. Substitution of Cu and Fe increased the specific capacitance (Csp) from 607 to 1350 F g−1 and 410 to 1237 F g−1 in stiff and flexible electrodes, respectively. Calculations of Csp from cyclic voltammetry (CV) profiles revealed a strong dependence on electrolyte molarity for all spinels studied, irrespective of whether stiff or flexible current collectors were used. A shift in anodic and cathodic peak positions in the CV profiles with increasing scan‐rates indicates rapid Faradaic kinetics at the electrode/electrolyte interface and the dominance of a capacitance‐controlled process. Electrochemical impedance spectroscopy analysis demonstrated low internal resistance, below 0.5 Ω, in all spinels, affirming the easy movement of electrolyte ions toward electrochemically active sites. Thus, this study illustrates the potential of these spinels as efficient electrode materials for supercapacitor applications that could be used in wearable electronics employing a KCl electrolyte and flexible copper current collectors.
Enhanced power density in solid oxide fuel cells using nickel-assisted gadolinium-doped ceria anodes Nacer Badi, Aashis S. Roy, Raghavendra Sagar, Saleh A. Alghamdi, Abdulrhman M. Alsharari, Alex Ignatiev Plos One, 2025 This study demonstrates the use of Gadolinium-doped ceria (GDC) (Ce₀.Gd₀.₂O₂) as the anode, BaNb₄MoO₂₀ (BNMO) as the electrolyte, and Lanthanum strontium cobalt oxide (LSCO) (La₀.Sr₀.₄CoO₃) as the cathode in the fabrication of a solid oxide fuel cell (SOFC). The synthesized nanocomposites were characterized using Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) for structural analysis, and scanning electron microscopy (SEM) for surface morphology assessment. DC conductivity measurements revealed that LSCO exhibited a high conductivity of 5.2 S/cm, attributed to the efficient flow of electrons through the electrolyte, highlighting its potential as a promising cathode material. Nyquist plots displayed semi-circular arcs, which correspond to distinct electrochemical processes within the system. The diameter of these arcs reflects the charge transfer resistance, primarily due to grain boundary resistance, while the initial resistance preceding the arc is associated with the bulk properties of the electrolyte. Beyond the first semicircle, diffusion resistance increases with frequency as a result of electrode polarization. It was also observed that the cell voltage dropped in discrete steps when the current density reached 200 mA/cm2. Specifically, the voltage decreased from 0.75 V to 0.53 V at 500°C, and from 0.98 V to 0.73 V at 800°C, likely due to charge transfer resistance at the electrode-electrolyte interface. The power density curve indicated that the cell achieved power densities of approximately 0.094, 0.118, 0.146, and 0.184 W/cm2 at operating temperatures of 500, 600, 700, and 800°C, respectively, demonstrating favorable performance for an SOFC employing BNMO as the electrolyte.
Metal Oxide Thin Films as Anti- Reflection Coatings for Enhancing the Photon to Energy Conversion Efficiency of Photovoltaic Cells Raghavendra Sagar Metal Oxides Advances in Sustainability and Nanotechnology, 2025 Development of anti-reflection coatings (ARCs) is one of the preferred ways to modify the surface of photovoltaic device (PV) and trap the photons within the device structure to boost the photon to energy conversion efficiency. Metal oxides in thin films with comparable refractive index and optimal thickness normally in nanometres are considered as potential contenders as ARCs due to their tuneable optical and matching electrical properties. ARCs facilitate the entry of additional photons within the photovoltaic layers and produce excess electron-hole pairs. Later, the inherent potential difference supports a parting of electron-hole pairs and facilitates the motion of charges. At present, Si3N4 is a commercial ARC used on Si-based photovoltaic cells to lessen the reflection from the top surface of the device. However, its inherent limitations and abundant availability of metal oxide sources with tuneable optical and electrical properties encourages alternate metal oxide based ARC materials to be found. In this chapter, fundamentals of ARCs, a deposition method of developing efficient ARCs using metal oxide on photovoltaic devices, its structure, microstructure, optical and efficiency measurements are discussed to prove their ARC characteristics.
Modified Zirconia as an Efficient Thermal Barrier Coating: A Case Study on ZrO2-Based Coatings Raghavendra Sagar, Nacer Badi Handbook of Zirconia Based Materials Manufacturing Electrochemical and Biomedical Engineering, 2025 The need for highly efficient engineering machineries such as jet engines and gas turbines that can withstand extremely harsh thermal environments has led us to explore new measures to ensure their sustainable performance. Among numerous measures, the development of thermal barrier coatings (TBCs) is one of the most preferred ways to overcome performance issues such as durability and lifespan of advanced engineering components subjected to high temperatures and corrosive and irradiation conditions. Rare earth ions stabilize zirconia due to its high structural, chemical, and thermal stability, and zirconia is one of the most extensively reported functional oxides used as TBC materials and is successfully deployed in many commercial engineering components due to its ability to endow superior thermal insulation. This chapter elucidates the strategies adopted for developing zirconia-based TBCs and how rare earth ions such as yttrium, cerium, and lanthanum can influence TBC performance. Finally, a case study on the use of zirconia-based TBCs in combustion engine components of automobiles is discussed in terms of its improvement in durability and efficiency.
Electrochemical performance of CuMn 2 O 4 spinel as a sustainable electrode material employed for high-performance supercapacitors on stiff and flexible copper … R Sagar, VS Bhat, CR Rajashekhar Bulletin of Materials Science 49 (2), 90 , 2026 2026
Internal Coatings to Prevent Slurry Erosion in Pipelines N Acharya, R Sagar, N Badi Slurry Erosion, 166-181 , 2026 2026
Metal Oxide Thin Films as Anti-Reflection Coatings for Enhancing the Photon to Energy Conversion Efficiency of Photovoltaic Cells R Sagar Metal Oxides, 163-182 , 2025 2025
Modified Zirconia as an Efficient Thermal Barrier Coating: A Case Study on ZrO2-Based Coatings R Sagar, N Badi Handbook of Zirconia-Based Materials, 154-175 , 2025 2025
Pseudocapacitive Behavior of (Fe, Cu) Based Co 3 O 4 as High-Performance Electrode Materials for Solid-State Stiff and Flexible Supercapacitors K Samatha, R Sagar ENERGY TECHNOLOGY 13 (11) , 2025 2025 Citations: 1
Comprehensive study on the adsorption properties of cobalt and nickel substituted Fe3O4 towards arsenic remediation R Sagar Inorganic Chemistry Communications, 115279 , 2025 2025
Enhanced power density in solid oxide fuel cells using nickel-assisted gadolinium-doped ceria anodes N Badi, AS Roy, R Sagar, SA Alghamdi, AM Alsharari, A Ignatiev PLoS One 20 (6), e0326559 , 2025 2025
Hibiscus leaf petiole derived activated carbon as a potential sorbent for basic green 4 and reactive yellow 15 dye exclusion from aqueous solution AA Kamath, NG Nayak, R Sagar, AK Kamath Inorganic Chemistry Communications 168, 112903 , 2024 2024 Citations: 6
Electrical and electrochemical characterization of FeCo 2 O 4 nanoflakes for flexible supercapacitor applications K Samatha, R Sagar Bulletin of Materials Science 47 (3), 163 , 2024 2024 Citations: 9
Prelithiation of electrodes in lithium-ion capacitors: A review AS D’Silva, MP Eldho, K Lekha, J Anushree, VS Bhat, R Sagar Mechanical Engineering Advances 2 (2), 1223-1223 , 2024 2024
RF sputtered metal oxide layers as ARCs to improve photovoltaic performance of commercial monocrystalline solar cell R Sagar, A Rao Optical Materials 150, 115276 , 2024 2024 Citations: 8
High specific capacitance and NTC behavior of substituted cobalt oxide spinels for electrochemical supercapacitor and thermistor applications K Samatha, R Sagar Inorganic Chemistry Communications 160, 112017 , 2024 2024 Citations: 4
A review on Co 3 O 4 nanostructures as the electrodes of supercapacitors S Kelathaya, R Sagar Mechanical Engineering Advances 2 (1), 111-111 , 2024 2024 Citations: 6
CoMn2O4 and Cu0. 5Co0. 5Mn2O4 spinels as efficient protective coating layers on SUS430 for SOFC interconnect N Acharya, R Sagar Ceramics international 49 (17), 29164-29173 , 2023 2023 Citations: 20
Microstructure, spectral and frequency dependent electrical studies of Ni-and Zn-substituted Co 3 O 4 spinels for capacitor applications K Samatha, R Sagar Bulletin of Materials Science 46 (1), 49 , 2023 2023 Citations: 6
Highly dense Mn3O4 and CuMn2O4 spinels as efficient protective coatings on solid oxide fuel cell interconnect and their chromium diffusion studies N Acharya, U Chaitra, H Vijeth, R Sagar Journal of Alloys and Compounds 918, 165377 , 2022 2022 Citations: 31
Electrical and electrochemical properties of nanostructured Ni and Zn substituted Co3O4 spinels for thermistors and supercapacitor applications K Samatha, H Vijeth Journal of Energy Storage 52, 104871 , 2022 2022 Citations: 28
Coconut flower sheath derived activated charcoal as efficient and cost effective adsorbent for crystal violet dye removal AA Kamath, NG Nayak, R Sagar Inorganic Chemistry Communications 134, 109077 , 2021 2021 Citations: 23
Structure and electrical properties characterization of NiMn2O4 NTC ceramics N Acharya, R Sagar Inorganic Chemistry Communications 132, 108856 , 2021 2021 Citations: 41
Growth, characterization and SHG studies of Cu (II) doped manganese sulfate monohydrate crystals R Sagar, A Rao, C Prathap Optical and Quantum Electronics 53 (9), 519 , 2021 2021 Citations: 5
MOST CITED SCHOLAR PUBLICATIONS
Complex impedance and modulus studies of cerium doped barium zirconium titanate solid solution R Sagar, RL Raibagkar Journal of alloys and compounds 549, 206-212 , 2013 2013 Citations: 55
Nanoscale TiO2 and Ta2O5 as efficient antireflection coatings on commercial monocrystalline silicon solar cell R Sagar, A Rao Journal of Alloys and Compounds 862, 158464 , 2021 2021 Citations: 42
Structure and electrical properties characterization of NiMn2O4 NTC ceramics N Acharya, R Sagar Inorganic Chemistry Communications 132, 108856 , 2021 2021 Citations: 41
Increasing the silicon solar cell efficiency with transition metal oxide nano-thin films as anti-reflection coatings R Sagar, A Rao Materials Research Express 7, 016433 , 2020 2020 Citations: 38
Electrical properties and microwave dielectric behavior of holmium substituted barium zirconium titanate ceramics R Sagar, P Hudge, S Madolappa, AC Kumbharkhane, RL Raibagkar Journal of alloys and compounds 537, 197-202 , 2012 2012 Citations: 38
Synthesis, structure and electrical studies of praseodymium doped barium zirconium titanate R Sagar, S Madolappa, N Sharanappa, RL Raibagkar Materials Chemistry and Physics 140 (1), 119-125 , 2013 2013 Citations: 32
Highly dense Mn3O4 and CuMn2O4 spinels as efficient protective coatings on solid oxide fuel cell interconnect and their chromium diffusion studies N Acharya, U Chaitra, H Vijeth, R Sagar Journal of Alloys and Compounds 918, 165377 , 2022 2022 Citations: 31
Electrical and electrochemical properties of nanostructured Ni and Zn substituted Co3O4 spinels for thermistors and supercapacitor applications K Samatha, H Vijeth Journal of Energy Storage 52, 104871 , 2022 2022 Citations: 28
Electrical, dielectric and pyroelectric behavior of neodymium substituted barium zirconium titanate R Sagar, S Madolappa, RL Raibagkar Solid state sciences 14 (2), 211-215 , 2012 2012 Citations: 25
Coconut flower sheath derived activated charcoal as efficient and cost effective adsorbent for crystal violet dye removal AA Kamath, NG Nayak, R Sagar Inorganic Chemistry Communications 134, 109077 , 2021 2021 Citations: 23
CoMn2O4 and Cu0. 5Co0. 5Mn2O4 spinels as efficient protective coating layers on SUS430 for SOFC interconnect N Acharya, R Sagar Ceramics international 49 (17), 29164-29173 , 2023 2023 Citations: 20
Comparative study on structure, dielectric and electrical properties of cobalt-and zinc-substituted Mn3O4 spinels N Acharya, R Sagar Applied Physics. A, Materials Science & Processing 126 (7), 515 , 2020 2020 Citations: 19
Antimicrobial activity of silver nanoparticles synthesized by Streptomyces species JF714876 GM Vidyasagar, B Shankaravva, R Sagar, RL Raibagkar International Journal of Pharmaceutical Sciences and Nanotechnology (IJPSN … , 2012 2012 Citations: 17
Structural and electrical studies of nanocrystalline Mn3O4 R Sagar Ferroelectrics Letters Section , 2018 2018 Citations: 16
NTCR behavior of Sm-substituted barium zirconium titanate nanocrystalline solid solution R Sagar, S Madolappa, RL Raibagkar Solid state communications 151 (24), 1949-1952 , 2011 2011 Citations: 13
Structural and electrical studies of Ni- and Co-substituted Mn 3 O 4 R Sagar, AS Gandhi Applied Physics A 127 (2), 84 , 2021 2021 Citations: 11
Dielectric and Impedance Studies of Ce-Doped Ba(Zr 0.52 Ti 0.48 )O 3 R Sagar, S Madolappa, RL Raibagkar Integrated Ferroelectrics 130 (1), 21-26 , 2011 2011 Citations: 10
Electrical and electrochemical characterization of FeCo 2 O 4 nanoflakes for flexible supercapacitor applications K Samatha, R Sagar Bulletin of Materials Science 47 (3), 163 , 2024 2024 Citations: 9
Surface modification of silicon solar cell using TiO2 and Ta2O5: fabrication and characterization R Sagar, A Rao Applied Physics A 125 (859), 1-8 , 2019 2019 Citations: 9
RF sputtered metal oxide layers as ARCs to improve photovoltaic performance of commercial monocrystalline solar cell R Sagar, A Rao Optical Materials 150, 115276 , 2024 2024 Citations: 8