RESEARCH

Nanomaterials hold promise for the future, and are expected to bring revolutionary changes, specifically in the area of renewable energy. Meeting the global energy challenge will require new technologies based on advanced energy devices using multifunctional materials. Our research lies in the broad areas of Nanoscience and Energy technology, in particular, development of novel nanostructured materials for energy storage and conversion applications. Our research focuses on the materials science and physics of various energy storage and conversion systems that will have great impact on our society. Some of our broad areas of interest include Carbon nanostructures- CNTs and Graphene, 2-dimensional layered nanostructures- MoS2, WS2, Supercapacitors, Lithium and Sodium batteries, Gas Storage. We do various experimental analyses to understand the underlying physical phenomena in these systems. Some of our current research interests include:

  • Synthesis of Carbon nanotubes, Graphene, MoS2, WS2, MoSe2 and composites
  • Template fabrication of hybrid nanostructures
  • Metal/metal oxide/polymer nanowires and composites
  • Lithium/Sodium - ion battery, Li-Sulphur battery, Supercapacitor
  • Gas storage in nanoporous materials- CO2, H2, CH4

Some of our recent research accomplishments are summarized below:

1. Multifunctional nanostructured materials:

(i) Synthesis of 2-dimensional layered nanostructures:  In one of our recent published works, we demonstrated size-controlled synthesis of luminescent quantum dots of MoS2 with a narrow size distribution, ranging from 2.5 to 6 nm and consisting of single/few layer thickness, from their bulk material, using a unique electrochemical etching of bulk MoS2. Excitation-dependent photoluminescence emission is observed in the MoS2 QDs and they exhibited excellent electrocatalytic activity towards hydrogen evolution reaction. In another work, we reported the synthesis of hetero-dimensional nanostructures of MoS2 quantum dots interspersed few-layered sheets of MoS2, using liquid exfoliation technique in organic solvents. This unique hybrid morphology results from the optimized experimental conditions involving bath sonication followed by ultrasound probe sonication. We showed that such hetero-dimensional hybrid materials could easily be extracted from the solvent as precipitates when post-treated with less polar volatile solvents such as chloroform. Such tailored MoS2 nanostructures, when directly used as electrodes for hydrogen evolution reaction (HER), showed excellent electrocatalytic activity with low over potential

  
Schematic representation of the electrochemical exfoliation of MoS2 [Deepesh et al., Chem. Commun., 51, 6293-6296 (2015)]   
 

Schematic and TEM images showing the MoS2 QDs interspersed MoS2 nano sheets [Deepesh et al., ACS Nano, 8, 5297-5303 (2014)]

2. High performance Energy Storage Devices: Rechargeable Lithium/Sodium batteries: 

The urgent need of the alternate renewable energy sources to fulfill the increasing energy demand of modern life has been recognized. These alternate energy sources are critical to tackle the daunting environmental issues by replacing the currently dominant fuels, petroleum and natural gas. Therefore considerable effort has been attempted to find better alternate and partial success is achieved in the area of renewable energy sources as well as energy storage devices. However, these devices suffer from various issues such as high cost, safety, performance, and hence do not meet the desired standards. The major reason of their inefficiency is the unavailability of advance materials with diverse multifunctional capability to deal the current requirement for future energy devices. We currently work on the design and development of high performance energy storage systems using novel nanoarchitectured materials and components.

(i) Graphene-based composite electrodes for Li-ion battery applications: Development of electrode materials for energy storage having both high energy and power densities along with good cyclic stability still remains a big challenge. Graphene-based nanocomposites have been prepared using simple hydrothermal route and were studied as efficient electrodes for Li-ion battery device applications. Graphene nanocomposite with good mechanical flexibility, high surface area and improved structural integrity, enhances the kinetics of lithium intercalation due to short diffusion path for Li+ transport, resulting in high power capabilities. Several such composite materials have been studied over the last four years. For example, TiNb2O7/Graphene and Nb2O5/Graphene nanocomposite electrodes showed superior electrochemical performances when studied as anodes for Li-ion batteries, resulting from their synergistic effects. We also demonstrated a single step strategy capable of improving specific capacity, power capability and faradic yield of a Li/CFx battery system. The excellent electrochemical performance achieved here using fluorinated graphene with a very low fluorine content (x=0.22) could lead to the development of highly efficient primary battery systems with low cost and minimum environmental impact.

Organic materials based electrodes for rechargeable Lithium battery  [Sharma, Dijo et al., J. Phys. Chem. Lett., 2013]

Fluorinated graphene based electrodes for Primary lithium battery [Dijo et al., RSC Advances, 2013]
 

Nb2O5/Graphene and its electrochemical properties  [Arunkumar et al.,RSC Advances (2015)]

          3. Nanoporous materials for gas storage applications: Designing nanoporous materials with high surface area, large porosity, superior structural stability and amenability to various processing conditions, is important to meet the commercial demands of large-scale reversible gas storage systems. Recently we demonstrated a simple approach to synthesize highly porous activated graphene-derived carbon (a-GDC), with ultra-high surface area (~3240 m2g-1) and enhanced porosity characteristics, from thermally exfoliated graphite oxide (TEGO), through an efficient and finely controlled KOH chemical activation process. a-GDCs with highly interconnected network of micro and mesopores showed excellent gas storage properties for CO2, CH4 and H2, with exceptionally high adsorption capacities and fast sorption kinetics, superior to other high surface area nanoporous carbons. In another earlier effort, we studied gas storage behaviour and electrochemical charge storage properties of high surface area activated nanoporous carbon, obtained from rice husk through low temperature chemical activation approach.


Schematic representation of synthesis of Graphene oxide-derived porous carbon and a graph showing its gas adsorption properties.