A theoretical investigation is highly important to investigate the properties of materials, the origin of selectivity, and the effect of various parameters in designing promising electrode materials for supercapacitor applications. The latest research paper by Mr Samadhan Kapse, PhD Student in the Department of Physics, and Prof Ranjit Thapa, Associate Dean of SEAMS (Sciences), envisions this and developed a novel VS2-BP hybrid electrode material. Their article titled All-solid-state Supercapacitor Based on Advanced 2D Vanadium disulfide/Black Phosphorus Hybrids for Wearable Electronics has been published in the journal ACS Applied Energy Materials with an impact factor of 6.959.

Abstract

Vanadium disulfide-Black Phosphorus (VS2-BP) hybrids were synthesised by a one-pot hydrothermal assisted method to achieve enhanced electrochemical activity for supercapacitor applications. The concentration of BP was optimised to prevent the restacking nature of VS2 and to enrich the active edges for electrolytic ion intercalation. The charge storage kinetics of the best-performing VS2-BP as an active electrode has demonstrated the dominance of the pseudocapacitive nature of the material. Further, by sandwiching with PVA/K2SO4 gel electrolyte, an all-solid-state (ASS) Vanadium disulfide/Black Phosphorus-50 mg (VS2-BP-50) symmetric device was developed on highly conductive carbon paper. The ASS VS2-BP-50 symmetric device displays the highest specific areal capacitance of 203.25 mF/cm2. It exhibits the maximum areal energy density of 28.22 µW h cm-2 at an areal power density of 596.09 mW cm-2, outperforming previous literature. We used density functional theory to understand the origin of high quantum capacitance. We found that the charge accumulation region between VS2 and BP monolayers and the charge transfer is the origin of the improved density of states in the VS2-BP hybrid. Also, we observed the higher mobility of K+ ion and a higher diffusion rate using the Density functional theory (DFT) method.

Explanation of the research

A novel VS2-BP hybrid electrode material was prepared using a simple hydrothermal approach. Due to a synergistic effect, it was discovered that adding BP to metallic VS2 enhances the number of electrochemically active sites, resulting in increased surface activity. It also accelerates reaction kinetics with electrolyte ions by improving the electrical behaviour of active electrode material. As a result, the hybrid technique overcomes the weaknesses of individual components during electrochemical processes, resulting in increased performance that has been limited by individuals. The BP nanosheets behaved as a pore region for electron transport and prevented the VS2 layers from re-stacking. Systematic experiments are conducted by selecting the ideal precursor ratios to generate a high-quality VS2-BP hybrid with enhanced electronic conductivity. Furthermore, in the overall collective charge storage of the VS2-BP-50 hybrid material, the present results demonstrated that capacitive contributions outnumber diffusive contributions. The ASS VS2-BP-50 symmetric supercapacitor device was also designed to have a high areal capacitance of 203.25 mF/cm2 with a maximum areal power density of 596.09 mW cm-2. The extraordinary performance of the ASS VS2-BP-50 symmetric device illustrates its versatility in terms of designing a high-power density ASS supercapacitor for flexible and wearable device applications. The work functions of BP, VS2, and VS2-BP are 0.73 eV, 5.37 eV, and 4.99 eV, respectively, which help in the charge transfer mechanism and increase the density of state at the Fermi level, and subsequently, the quantum capacitance of the heterostructure.

Collaborations

1. Mr Aditya Sharma, Centre for Nano and Material Sciences, Jain Global Campus, Jakkasandra, Ramanagaram, Bangalore – 562112, Karnataka, India

2. Mr Ankur, Centre for Nano and Material Sciences, Jain Global Campus, Jakkasandra, Ramanagaram, Bangalore – 562112, Karnataka, India

3. Mr Sagar Bisoyi, Department of Physics, School of Applied Sciences, KIIT Deemed to be University, Bhubaneswar-751024, Odisha, India.

4. Dr Gopal K. Pradhan, Department of Physics, School of Applied Sciences, KIIT Deemed to be University, Bhubaneswar-751024, Odisha, India.

5. Dr Chandra Sekhar Rout, Centre for Nano and Material Sciences, Jain Global Campus, Jakkasandra, Ramanagaram, Bangalore – 562112, Karnataka, India

Social implications of the research

With the exponential development of portable/flexible electronics and the high demand for renewable energy, conventional energy-storage devices, such as supercapacitors, have attracted attention due to their benefits of fast charge/discharge rates, long cycle life, and high-power density. Similarly, developing novel functional materials with exceptional qualities could shed light on a plethora of challenges, including environmental pollution, energy crisis, etc. Two-dimensional (2D) layered materials, such as metallic 1T MoS2 single layers, SnSe2, MXenes, and black phosphorous (BP), have been intensively studied for supercapacitor applications. These materials benefit from efficient ion intercalation and electrosorption. The two-dimensional (2D) layered transition-metal dichalcogenides (TMDs) have recently piqued the scientific community’s curiosity.

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The latest research at the Department of Physics is investigating the charge transport across protein-based molecular junctions. Researchers envision fabricating bio- FETs which is useful in electronic devices as an alternative to Si- technology. Assistant Professor Dr Sabyasachi Mukhopadhyay and his PhD scholar Kunchanapalli Ramya published their paper Modulation of optoelectronic and mechanical properties across (bio) molecular junctions under external stimuli in the journal of Electronic Materials with an impact factor 2.04.

Abstract

Molecular junctions are formed by wedging molecules between two metal electrodes. Besides the conventional parameters of the metal-molecule-metal junction, such as the work function of electrodes and the molecules’ energy gap, molecule-electrode electronic coupling strength also plays a vital role in modulating the electronic properties of the molecular junction under external stimuli. We have also calculated several transport parameters which play a crucial role in finding the origin of conductance modulation under the external stimuli. We could find that before particular humidity conditions, the modulation in the conductance is due to the variation in coupling strength, which is due to the modulation in the electrostatic environment of retinal chromophores of protein by changing the structure of protein under various external stimuli.

Researchers have explored the external stimuli (illumination, force, and humidity conditions) effect on charge transport across bacteriorhodopsin-based molecular junctions. Their future research plans include bio- FET fabrication with the protein reported and studying the transistor characteristics across it.

Frontiers in Physics is a peer-reviewed scientific journal. It covers the entire field of Physics ranging from experimental to computational and theoretical physics. Assistant Professor Dr Jatis Kumar Dash from the Department of Physics has been invited to be a part of the Editorial Board of this prestigious journal. The multidisciplinary journal focuses on applied physics and has an impact factor of 3.560.

Dr Jatis Kumar Dash feels honoured to receive the invitation to join the Editorial Board. He finds it satisfying to get involved in scrutinising and reviewing manuscripts that concentrate on materials, experimental and condensed matter of Physics, and related devices. The process of reviewing these manuscripts enriches his knowledge in the subject domain. This helps him widen his research horison and explore novel ideas. The tenure of his role as an editor is not defined but is expected to last for five years.

Research at the Department of Physics envisions future studies on the anisotropic properties across various planes of their reported MAPbBr3 crystals and identifying the better plane for efficient electrical contact in device applications. Assistant Professor Dr Sabyasachi Mukhopadhyay and his research scholar Kunchanapalli Ramya recently published the paper Room-Temperature Cost-effective In-situ grown MAPbBr3 Crystals and their Characterization towards Optoelectronic Devices in the journal Material Science and Engineering: B. The paper has an impact factor of 3.407. They have done this work in collaboration with Sr Satyajit, IIT- Bhilai. This is the first article published under the Indo- Israel bilateral project A Halide Perovskite-Based Photoanode for Oxygen Evolution Reaction Using a Molecular Diode in a Hybrid Nanometer Scale.

Abstract

The paper reports the in-situ, room-temperature synthesis of methylammonium lead bromide CH3NH3PbBr3 crystals using N-methyl formamide as a source of methylammonium (MA+) ions during the crystallization process to explore the structural, dielectric, and electronic properties of CH3NH3PbBr3 crystals for optoelectronic applications. Optical absorption and radio-luminescence measurements affirm the direct bandgap nature of the crystals. Impedance spectroscopy measurements with various applied AC voltages within the 20 Hz – 10 MHz frequency range depict the influence of ionic motions on electrical transport across crystal planes. Researchers have extracted electrical transport parameters in CH3NH3PbBr3 crystals from the Nyquist plots, which we found to be distinctly varied wherein two different AC voltage amplitude regimes, broadly for 10 – 50 mV and 100 – 500 mV AC voltage range.

Explanation of the research

The wide approachability of our synthesis method lies in avoiding expensive precursor salts and eliminating the use of toxic solvents. We have obtained the MAPbBr3 crystals with improved thermal, optical, and dielectric properties that are used in optoelectronic devices, mainly in the applications of solar cells and photodetectors.

A two-day DST-INSPIRE Subject Expert Committee meeting was held on July 14 & 15 at SRM University-AP campus. Experts in the area of Physical Sciences from across the country gathered at the university to evaluate this year’s INSPIRE Fellowship applications in Physical Sciences.

INSPIRE Fellowship component offers 1000 Fellowships every year for carrying out doctoral degrees in both basic and applied sciences, including engineering and medicine, in the age group of 22-27 years.

The Chairperson of the Expert Committee in the area of Physical Sciences was Dr Dinakar Kanjilal, Professor, Inter-University Accelerator Centre (IUAC), New Delhi. “The fellowship ensures geographical distribution of excellence, and we look forward to more applicants from SRM AP”, Prof. Kanjilal said. Since its inception, SRM University-AP has INSPIRE Fellows as faculty members in the various departments of Sciences.

University Pro-Vice-Chancellor Prof D Narayana Rao, who also is the co-chair of the expert committee, said that it is gratifying to know that the PhD students have chosen to enrol in reputed universities and institutes. The applicants have chosen extremely accomplished scientists and faculty members as their research supervisors. “We are glad that 61 are girl students out of the 116 applications we received”, highlighted Prof D Narayana Rao. He expressed his happiness about the increasing number of women representation in Indian academia.

The other eminent scientists in the INSPIRE Fellowship selection committee included Member Secretary Dr Umesh K Sharma, Prof. Shikha Verma, Dr G. Vijaya Prakash, Dr AnandamayeeTej, Dr Rajendra Prasad Pant and Dr Arjit Chowdhuri.

Innovation in Science Pursuit for Inspired Research (INSPIRE)” is a flagship scheme of the Department of Science and Technology (DST), Government of India, which aims to attract meritorious youth to study basic and natural sciences at the college and university level and to pursue research careers in both basic and applied science areas including engineering, medicine, agriculture, and veterinary sciences.