Ph.D. THESIS COLLOQUIUM
Speaker: Ankit Kumar
Research Supervisors: Professor A K Shukla and Professor Satish Patil
Thesis Title: Studies on Nanostructured Transition Metal Oxides and Related Composites as Supercapacitor Electrodes
Date & Time: 17 January 2022 at 4:00 pm through Microsoft Teams
Supercapacitors have acquired considerable scientific and technological place in energy storage owing to their compelling power capability, good energy density, excellent cycling stability and ideal safety. High-performance supercapacitors have been realized by nanostructured electrode designs, which provide ameliorated surface area for abundant electrode-electrolyte interaction, ease of electron transfer and movement, and short ion-diffusion pathways, that lead to increased performance. Transition metal oxide (TMO)-based electroactive materials are of significant interest owing to the remarkable combination of structural, mechanical, electrical, and electrochemical properties. Besides their high specific capacitance and energy density, the stable redox chemistry, highly reversible and fast charge-discharge processes, low cost, and environment friendly processes make them the most promising materials for next-generation supercapacitors . In the light of the foregoing, in the thesis efforts are made to synthesize transitional metal oxides (TMOs) and related composites with varying nanostructures and characterize them as materials for supercapacitors.
Mn3O4 and Fe3O4 nanoparticles (NPs) anchored over carbon nanotube (CNT) are synthesized by direct decomposition of metal-hexacyanoferrate complex on the CNT surface. NPs are discretely attached over CNT surface without forming a uniform layer, thus making most of the NP surface available for electrochemical reactions. Assembled (-) CNT-Fe3O4//(+) CNT-Mn3O4 asymmetric supercapacitor(ASC) can provide 0.0V-1.8V potential window in aqueous 1 M Na2SO4 electrolyte. ASC can deliver an energy density of 37 Wh/kg and power density 10.3 kW/kg with excellent cycling stability .
Free-standing MoS2/r-GO with expanded interlayers are grown on molybdenum (Mo) foil. Interlayer expansion in MoS2 enables Na+-ions intercalation/deintercalation facilitating enhanced capacitance, rate capability and cycling stability of capacitor in 1 M Na2SO4 electrolyte. When MoS2/r-GO anode is assembled with Fe2O3/MnO2 cathode, namely (-) MoS2/r-GO//(+) Fe2O3/MnO2, as an ASC, it can deliver a volumetric energy density of 0.78 mWh/cm3 at volumetric power density 500 mW/cm3 .
Fe/Fe3C nanoparticles are investigated as anode material for supercapacitor application. Fe/Fe3C nanoparticles encapsulated in graphitic carbon are formed by one step synthesis by pyrolyzing single source precursor Prussian Blue (Iron (III) ferrocyanide). The porous structure of the material facilitates electrolyte ion diffusion, while metallic iron enhances the electronic conductivity. The assembled (-) Fe/Fe3C//(+) activated carbon ASC can deliver energy density of 12 Wh/kg and power density of 11.8 kW/kg with super cycling stability up to 20000 cycles in 1 M KOH electrolyte .
RuS2 nanosheets are synthesized by pyrolyzing RuO2 with sulfur in inert nitrogen atmosphere. A 2V (-) activated carbon//(+) RuS2 ASC can deliver high volumetric energy density of 1.57 mWh/cm3 at volumetric power density of 23.71 mW/cm3 with excellent cycling stability in 1 M Na2SO4 electrolyte .
Finally, as three of the 12 V Lead-Carbon hybrid ultracapacitors connected in series to form a 36 V hybrid ultracapacitor are found to yield uneven performances, a voltage-management cell-balancing circuitry is demonstrated to be useful for realising synchronised performance from each of the 12 V hybrid ultracapacitor unit.
- Kumar, A.; Rathore, H. K.; Sarkar, D.; Shukla, A. Nanoarchitectured Transition Metal Oxides and Their Composites for Supercapacitors. Electro. Sci. Adv. 2021, e21008, 1-42.
- Kumar, A.; Sarkar, D.; Mukherjee, S.; Patil, S.; Sarma, D. D.; Shukla, A. Realizing an Asymmetric Supercapacitor Employing Carbon Nanotubes Anchored to Mn3O4 Cathode and Fe3O4 Anode. ACS Appl. Mater. Interfaces 2018, 10, 42484-42493.
- Sarkar, D.; Das, D.; Das, S.; Kumar, A.; S.; Patil, S.; Nanda, K. K.; Sarma, D. D.; Shukla, A. Expanding Interlayer Spacing in MoS2 for Realizing an Advanced Supercapacitor. ACS Energy Lett. 2019, 4, 1602-1609.
- Kumar, A.; Das, D.; Sarkar, D.; Patil, S.; Shukla, A. Supercapacitors with Prussian Blue Derived Carbon Encapsulated Fe/Fe3C Nanocomposites. J. Electrochem. Soc. 2020, 167, 060529.
- Kumar, A.; Das, D.; Sarkar, D.; Nanda, K. K.; S.; Patil, S.; Shukla, A. Asymmetric Supercapacitors with Nanostructured RuS2. Energy Fuels 2021, 35, 12671-12679