Studies and research on air pollution have sparked worldwide interest in the recent decades to overcome the imminent threat of air pollution. The air filtration mechanism is one of the efficient ways to capture particulate matter (PM) and purify the air. An innovatory air filtration mechanism blending polyacrylonitrile (PAN)/polyvinylpyrrolidone (PVP) polymer nanofibers has been proposed by Prof Ranjit Thapa and his PhD scholar Deepak S Gavali from the Department of Physics.

The paper “Low Basis Weight Polyacrylonitrile/Polyvinylpyrrolidone Blended Nanofiber Membranes for Efficient Particulate Matter Capture” was published in collaboration with Applied NanoPhysics Laboratory, Department of Physics and Nanotechnology, SRM Institute of Science and Technology, Kattankulathur. It was featured in the journal ‘ACS Applied Polymer Materials’ having an Impact Factor of 4.09.

In the twenty-first century, air pollution is a major problem facing human and environmental health. Every year, millions of people die, mostly in developing nations, owing to the aggravating level of air pollution. According to the World Health Organization (WHO), 92 per cent of the people live in places where the air quality level has crossed the WHO limits. Particulate matter (PM) (solid or liquid particles with different aerodynamic diameters), nitrogen dioxide (NO2), ozone (O3), and others are the relevant air contaminants.

In low-income cities, the effect of PM 2.5 pollution is high due to high urban air pollution. Even at very low concentrations, PM 2.5 (particles with an aerodynamic diameter less than 2.5 µm) pollution has health consequences. Air filtration is one of the best remedies to tackle such problems and maintain a clean environment for humans. Among the available air filter materials, fiber-based air filters have proven to be the most potentially effective treatment, due to their high porosity, high surface area, lightweight, etc.

This study relies on a careful design that blends PAN and PVP fibers. The resultant nanofiber material is utilized to overcome the low air pressure resistance issue with high filtration efficiency. Large-scale free-standing nanofibers were obtained by a simple peeling-off process. The morphology, chemical interaction between the filter media and PM pollutant; and filtration properties were investigated. Compared to commercial mask, the semi- high-efficiency particulate air (HEPA) filter media, PAN/PVP filter medium showed superior performance in PM 2.5 filtration. Furthermore, the intermolecular interactions between PMs and nanofibers were analyzed by DFT calculations. With constant optimization of synthesis conditions, the synthesized air filters achieved high filtration efficiency for PM removal and showed great potential for practical application.

Abstract of the Research

Particulate matter (PM) in air frequently poses a serious threat to human health. Smaller PM can easily enter into the alveolus and blood vessels with airflow. This work reports the first polyacrylonitrile (PAN)/polyvinylpyrrolidone (PVP) polymer blend nanofiber filter media for effectively capturing PM. Density functional theory (DFT) calculations are used to investigate the effect of the blending of two polymers on the dipole moment and the electrostatic potential. Based on the DFT calculations of the intermolecular interactions between nanofibers and PM, the PAN/PVP heteromolecular percentage is considered for experimental synthesis, which can provide better performance in the filtration of pollutants. The composite PAN/PVP fiber network was successfully developed and optimized to cope with complex environments during the actual filtration process. The role of the blending ratio of PAN and PVP in wt % was explored on PM 2.5 capture, and the refined ratio overcame the conflict between high filtration efficiency and low air pressure resistance. The air filter medium PAN/PVP (6:2) possesses an extremely high air filtration efficiency of 92% under a very low pressure drop of 18 Pa for a 0.5 g m–2 basis weight. Both polar and nonpolar functional groups in blend nanofibers promoted significantly the electrostatic attraction and improved the filtration efficiency under static and dynamic airflow. The PAN/PVP nanofiber membranes maintain outstanding air filtration under different temperature and humidity conditions. This study will shed light on the fabrication of high-efficiency low-basis weight nanofiber filter media as an end product.

The Department of Physics organised a Faculty Development Programme discussing the scopes of implementing sponsored projects. Renowned academicians, Prof Sathish Vadhiyar, IISc Bangalore; Prof Kothandaraman Ramanujam, IIT Madras; and Prof Paromita Chakraborty, SRMIST were the keynote speakers of the session. They shared their views and enlightened the faculty on the scopes and challenges in implementing projects proposed across various disciplines.

Prof V S Rao, Vice-Chancellor SRM-AP, welcomed the gathering. He appreciated the department’s effort in organising programmes on such impactful topics. Reminding the community of the inevitability of emphasising research, he congratulated all the faculty for their influential publications, sponsored projects, patent publications, etc. Prof D Narayana Rao, Pro-Vice-Chancellor, also addressed the gathering and reiterated the need to conduct such crucial discussions among administrators and policymakers. He further highlighted the importance of reorienting the vision of every Indian university by giving a special focus on research and development.

Prof Sathish Vadhiyar commenced the discussion by providing a brief overview of the National Super Computing Mission (NSM). It is one of the principal ventures funded by DST and MeItY to advance the overall high-performance computing ecosystem. He deliberated on the R&D projects involved in NSM, its objectives, proposal areas, budget, research allocations etc. Prof Ramanujam presided over and shared his experience in collaborating with industries to market the research product. He gave a detailed analysis of the functioning of consultation companies, types of consultancies, stages involved in such projects, and the different ways to attract funding. Prof Paromita Chakraborty was the last speaker of the day. She offered an elaborate outline for designing and developing a project proposal and concluded by imparting a few insights from her successful projects.

Prof Ranjit Thapa and his PhD scholar, Mr Samadhan Kapse from the Department of Physics have reported their euphoric achievement of discovering an economically viable electrocatalyst for effective green urea synthesis. The paper “Selective Electrocatalytic Co-reduction of N2 and CO2 on Copper Phthalocyanine for Green Urea Production” has been published in the highly prestigious Nature indexed journal, ‘Advanced Functional Materials’, having an Impact Factor of 18.81. It was published in collaboration with Jit Mukherjee, and Uttam Kumar Ghorai, from the Department of Industrial Chemistry & Applied Chemistry, Swami Vivekananda Research Centre.

With global annual production of 100 million tons, urea is one of the important nitrogen sources for the fertilizer industry. Industrial urea is synthesized by the following two consecutive steps. First, the reaction of nitrogen and hydrogen (N2 + H2 → NH3) by the Haber-Bosch process at high temperature and pressure (350–550°C, 150–350 bar); followed by the reaction of NH3 and CO2 [NH3 + CO2 → CO(NH2)2] under mild reaction conditions (170–200°C and 200–250 bar). The sequential reactions are carried out for several cycles to increase the conversion efficiency. For the first step, fixation of N2 is an energy as well as a capital intensive process due to difficulty in cleaving the N≡N bond. Extensive research works have been reported on electrochemical N2 fixation to NH3 in water medium under ambient conditions. In this electrochemical method, isolation of NH3 gas with high purity from electrolyte solution is troublesome. In the second step, CO2 fixation on the substrate and its separation is one of the major challenging tasks for the further reaction with NH3 to end up in urea formation. Overall, the two-step process for large scale production of urea consumes high energy and produces greenhouse gases for the environment.

The research team reported copper-phthalocyanine nanotubes (CuPc NTs) having multiple active sites as an efficient electrocatalyst which exhibits a tremendous yield of urea with good durability and long-term stability. DFT calculation predicts that Pyridinic–N1 in CuPc is responsible for N2 reduction and the metal centre plays an important role for CO2 reduction. This study not only provides us with the co-reduction of N2 and CO2 gases using cost-effective CuPc NTs catalyst but also opens a new pathway to the rational design of other transitional metal-based electrocatalysts having multiple active sites for N2 and CO2 gas fixation applications.

This electrochemical method of urea synthesis by the co-reduction of N2 and CO2 [N2 + CO2 + 6H+ + 6e– → CO(NH2)2 + H2O] using an efficient electrocatalyst in a water medium under ambient conditions would be an alternative way in the upcoming days. All the strategies using alloys and heterostructure for urea synthesis forming C–N bond by the co–reduction of N2 and CO2 have not reached the benchmark in terms of urea yield rate and FE for practical applications. To achieve a high urea yield and FE, various factors are to be considered in this work.

Abstract of the Research

Green synthesis of urea under ambient conditions by electrochemical co-reduction of N2 and CO2 gases using effective electrocatalyst essentially pushes the conventional two steps (N2 + H2 = NH3 & NH3 + CO2 = CO (NH2)2) industrial process at high temperature and high pressure, to the brink. The single-step electrochemical green urea synthesis process has hit a roadblock due to the lack of an efficient and economically viable electrocatalyst with multiple active sites for dual reduction of N2 and CO2 gas molecules to urea. Herein, the research reports copper-phthalocyanine nanotubes (CuPc NTs) having multiple active sites (such as metal centre, Pyrrolic-N3, Pyrrolic-N2, and Pyridinic-N1) as an efficient electrocatalyst which exhibits urea yield of 143.47 µg h-1 mg-1cat and FE of 12.99% at –0.6 V vs RHE by co-reduction of N2 and CO2. Theoretical calculation suggests that Pyridinic-N1 and Cu centres are responsible to form C–N bonds for urea by co-reduction of N2 to NN* and CO2 to *CO respectively. This study provides new mechanistic insight into the successful electro-reduction of dual gases (N2 and CO2) in a single molecule as well as the rational design of an efficient noble metal-free electrocatalyst for the synthesis of green urea.

The Department of Physics is happy to announce that Prof Ranjit Thapa and his PhD Scholar Mr Samadhan Kapse have published a paper titled “Supercapacitor electrodes based on quasi-one-dimensional van der Waals TiS3 nanosheets: experimental findings and theoretical validation” in the Nature indexed journal ‘Applied Physics Letters’ having an impact factor of 3.79. The Paper is published in collaboration with Abhinandan Patra and Chandra Sekhar Rout from Jain University and Dattatray J Late from Amity University.

Abstract of the Research

To cease the ever-increasing energy demand, additional enthusiastic focus has been given to generate more sustainable energy from alternative renewable sources. The storage of these energies for future usage solely depends on the energy storage devices. A diversity of electrode materials based on two-dimensional (2D) transition metals and their derivatives have enticed the whole world owing to their tunable properties. Transition metal trichalcogenides (TMTCs- MX3 type) is the emergent class of 2D materials that gathered a lot of interest because of their quasi-one-dimensional anisotropic properties with the van der Waals force of attraction in between the layers. Herein, TiS3 being an MX3-type of material is preferred as the electrode for supercapacitor application with detailed experimental investigations and theoretical validation. The highest capacitance attained for TiS3 is found to be 235 F/g (105 C/g) at 5 mV/s with a battery type of charge storage mechanism. The asymmetric device is fabricated using Ti3C2Tx MXene nanosheets as negative electrode and a brilliant 91 % of capacitance retention is accomplished with an extensive potential window of 1.5 V. The investigational discoveries are substantiated by theoretical simulation in terms of the quantum capacitance assessment and charge storage mechanisms.

About the Research

In this work, a battery type TMTC material i.e., TiS3 has been synthesized and characterized by different analytical techniques such as Raman spectroscopy, FESEM and TEM to gain information on its structural and morphological aspects. The electrochemical performance was found to be promising by considering its good energy storage performance. High capacitance of 235 F/g (105 C/g) at 5 mV/s was achieved and the asymmetric supercapacitor devices disclosed outstanding cycling stability of 91 % over 6000 GCD cycles. In addition, the theoretical simulations also validated the experimental findings through the evaluation of the quantum capacitance. The higher conductivity, abundant electrochemical active sites, swift faradic redox kinetics and well-connected pathway for ion transfer characteristics pave the way for TiS3 to emerge as an eminent material for energy storage application in the long run.

Social Implications

Energy storage devices come into picture whenever there is a prerequisite of storing renewable energy. Among the numerous energy storage devices, batteries and ultracapacitors have acquired more popularity in nanotechnology and optoelectronics field. The high stability, accuracy, swift functionality, power density and reversibility are the key factors that have positioned ultracapacitors at the forefront of all energy storage devices. On the contrary, the low energy density and high cost of supercapacitor electrodes try to put them in the back seat of the wheels of the energy industry. Henceforth, in recent times the development of supercapattery (abbreviated for supercapacitor and battery) types of materials has become a way out which tie the aces like high specific power of supercapacitors with the high energy density of batteries. These materials exhibit capacitive or battery type behaviour on the basis of materials properties, electrolytic ions, design of the electrochemical cell. Due to these advantages and superior energy storage performance, the demand for this kind of material is growing.

Theoretical quantum capacitance is an important parameter to investigate the supercapacitor performance of low dimensional materials such as electrodes. This approach is highly cost-effective for the rapid screening of various materials for supercapacitor applications.

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“Highly Efficient Catalysts of Ruthenium Clusters on Fe3O4/MWCNTs for Hydrogen Evolution Reaction” is the latest paper published by Prof Ranjit Thapa, Professor of Physics at SRM university-AP and his PhD scholar, Mr Samadhan Kapse, in ‘New Journal of Chemistry’ having an Impact Factor of 3.591.

In this work, the chemical co-precipitation technique is adopted to produce Fe3O4 nanoparticles under an inert atmosphere and was utilized for HER studies. The Ru nanoparticles were profitably deposited over Fe3O4/MWCNTs GC electrode using electrochemical deposition technique. The superior HER activity was achieved on Ru/Fe3O4/MWCNTs in 0.1 M H2SO4 aqueous media. We have demonstrated that the synthesized electrocatalyst offers a low overpotential of 101 mV to achieve a current density of 10 mA cm-2 towards the hydrogen evolution reaction. It displays long-term durability, exceptional cyclic stability even after 1000 cycles. DFT calculations imply that the availability of both octahedral and tetrahedral sites in Ru/Fe3O4/MWCNTs with low overpotential is more efficient towards HER. It is emphasized that a low percentage of ruthenium in the prepared catalyst can be substituted as a promising HER catalyst for sustainable energy technologies.

Abstract of the paper

Producing molecular hydrogen (H2) using water provides a sustainable approach for developing clean energy technologies. Herein, we report highly active ruthenium clusters (Ru) supported on iron oxide (Ru/Fe3O4) and Fe3O4/multi-walled carbon nanotubes (Ru/Fe3O4/MWCNTs) by simple electrochemical deposition in a neutral aqueous medium. The supported catalyst exhibits good hydrogen evolution reaction activity (HER) in an acidic environment. Cyclic voltammograms (CV) in potassium ferrocyanide (K4[Fe(CN)6]) confirm MWCNTs enhance the electron transfer process by decreasing the redox formal potential. The overpotential of Ru/Fe3O4/MWCNTs and Ru/Fe3O4 electrocatalysts versus reversible hydrogen electrode (RHE) was found to be 101 mV and 306 mV to reach a current density of 10 mA cm-2 . As prepared, the catalyst displays good stability and retain its HER activity even after 1000 cycles. Further, the stability of Ru/Fe3O4/MWCNTs was studied using chronopotentiometric (CP) technique for 12 hrs and found negligible loss in the catalytic activity towards HER. To explore the role of Ru and underneath MWCNTs to improve the catalytic performance of Fe3O4, density functional theory (DFT) calculations were carried out. DFT calculations indicate the octahedral site of Ru/Fe3O4 favours HER with low overpotential. However, Ru/Fe3O4/MWCNTs is more efficient towards HER could be due to the availability of both octahedral and tetrahedral catalytic sites.

Social implications of the research

Renewable energy generation is of greater importance in the present circumstances. This is caused by the depletion of non-renewable energy sources like fossil fuels and other hydrocarbon deposits and the release of greenhouse gases into the atmosphere. Hydrogen has gained considerable interest as an energy storage and energy carrier because of its high energy density (146kJ/g). Furthermore, its lightweight, profusion nature and the release of water during its combustion eliminate environmental pollution and thus contribute to defeating the global energy crisis. Also, hydrogen is an important and ideal energy source to develop fuel cells. A number of methods have been explored to generate molecular hydrogen. Among them, water electrolysis is a promising technology for generating high-purity hydrogen from water. An excellent electrocatalyst is obligatory to liberate hydrogen gas effectively from water. A higher HER activity is known to be obtained from platinum (Pt) and Pt-based catalysts. Given its high cost and low surplus, it limits expansion to the industrial scale. Over the few past decades, lots of efforts have been made by many research teams to find out alternative catalysts to substitute Pt electrodes.

The paper is published in collaboration with Shwetha Kolathur Ramachandra, Doddahalli Hanumantharayudu Nagaraju, and Shivanna Marappa; School of Applied Sciences, REVA University, Bangalore-560064, Karnataka, India. According to the research group, the density functional theory can boost the searching process of highly promising electrocatalysts for hydrogen evolution reactions in renewable energy generation.

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