Department Of Physics
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Item Synergistic improvement in electrochemical performance of Cr-doped MoS2/CuCo2S4 binary composite for hybrid supercapacitors(Elsevier Ltd, 2023-10-31T00:00:00) Kour, Pawanpreet; Kour, Simran; Deeksha; Sharma, A.L.; Yadav, KamleshThe synergistic effect of transition metal doping and composite formation can be imperative to improve the limited conductivity and inferior cyclic stability of MoS2 for supercapacitors. In this work, firstly, the impact of Cr-doping on the electrochemical activity of MoS2 has been discussed. Afterwards, the optimized Cr-doped MoS2 (CrMS-5) sample has been combined with CuCo2S4 (CCS) to further enhance its charge storage ability and cyclic stability. The CrMS-5/CCS composite delivers tremendous electrochemical activity as an electrode with a specific capacity of approximately 1324.08 C g?1 at 4 A g?1. The outstanding performance of the doped binary composite is on account of the synergism between doping and composite formation that results in increased conductivity and numerous redox active sites for charge storage. Furthermore, a symmetric supercapacitor device (SSC) has been fabricated using a CrMS-5/CCS electrode. It attains a high energy density of 46.63 Wh kg?1 corresponding to 1 kW kg?1 of power and exhibits remarkable cyclic stability of 81% for up to 5,000 cycles. The device illuminates a star-shaped LED panel of 12 red LEDs for 30 min. Thus, the above outcomes demonstrate the superiority of the doped MoS2-based composites for high-energy symmetric supercapacitors. � 2023 Elsevier LtdItem Effects of Dy3+-doping on the band-gap widening and formation of mixed cubic and monoclinic phases of Sm2O3 nanoparticles(Springer Science and Business Media Deutschland GmbH, 2023-10-30T00:00:00) Sain, Rachana; Roy, Ayan; Kumar, Ajay; Anu; Deeksha; Kour, Pawanpreet; Singh, Ravi Pratap; Yadav, KamleshWe synthesized Sm2?xDyxO3 (where X = 0.00, 0.03, 0.06, 0.09, and 0.12) nanoparticles using a co-precipitation method and investigated their structural and optical properties. X-ray diffraction (XRD) results reveal that Dy3+-doping in Sm2O3 nanoparticles leads to the formation of a monoclinic polymorphic phase along with the cubic phase of Sm2O3 and its fraction increases with increasing Dy3+-doping concentration. The substitution of Dy3+ at the Sm3+ site converts the cubic Sm2O3 unit cells into distorted monoclinic Sm2?XDyXO3 unit cells. The average crystallite and nanoparticle sizes decrease with increasing Dy3+-doping concentration. Dy3+-ions act as particle size inhibitors, which is attributed to an increase in the segregation of Dy3+-dopant ions at the surface of the nanoparticles with increasing Dy3+-doping content. The peak appearing at 851�cm?1 in the Fourier transform infrared spectroscopy (FTIR) spectra confirms the formation of Sm2O3. Widening of the band gap (Eg) above the band gap of pure cubic Sm2O3 with Dy3+-doping concentration has been observed for X > 0.06, which is due to the Moss-Burstein and quantum size effects. � 2023, The Author(s), under exclusive licence to Springer-Verlag GmbH, DE part of Springer Nature.Item MoS2-based core-shell nanostructures: Highly efficient materials for energy storage and conversion applications(Elsevier Ltd, 2023-04-19T00:00:00) Kour, Pawanpreet; Deeksha; Kour, Simran; Sharma, A.L.; Yadav, KamleshMolybdenum disulfide (MoS2) has acquired immense research recognition for various energy applications. The layered structure of MoS2 offers vast surface area and good exposure to active edge sites, thereby, making it a prominent candidate for lithium-ion batteries (LIBs), supercapacitors (SCs), and hydrogen evolution reactions (HERs). However, the limited conductivity, less number of active sites, and structural instability of MoS2 during continuous electrochemical cycling hinder its applications. In this regard, the formation of core-shell structures has been evolving as a prominent approach to uplift the electrochemical/electrocatalytic activity of MoS2 for energy-based applications. The unique core-shell composites of MoS2 with different electro-active materials exhibit superior electrochemical and electrocatalytic properties on account of the synergy of the core and the shell materials. These materials offer huge active area, high conductivity, an easy pathway for charge diffusion, and stable cyclic life leading to their outstanding electrochemical activity. In this review, various core-shell structures of MoS2 with carbon, metal oxides/sulfides, and conducting polymers are discussed for LIBs, SCs, and HERs. The function of core and shell materials in elevating the electrochemical activity of MoS2 based core-shell composites have been explored in detail. The effect of doping of core and shells on the performance of the composite has also been elucidated. The doped MoS2 based core-shell composites manifest tremendous electrochemical performance compared to the un-doped counterpart. Thus, these unique structured core-shell composites are regarded as futuristic candidates for energy storage and conversion systems. � 2023Item Effects of interfacial interactions on structural, optical, thermal degradation properties and photocatalytic activity of low-density polyethylene/BaTiO3 nanocomposite(Elsevier Ltd, 2023-04-10T00:00:00) Roy, Ayan; Panda, Sambit; Gupta, Jaya; Anu; Singh, Ravi Pratap; Deeksha; Kour, Pawanpreet; Sharma, M.P.; Yadav, KamleshBarium titanate (BaTiO3) filled low density polyethylene (LDPE), (LDPE)100?x/(BaTiO3)x (where x = 0, 2, 4, 6 and 10) nanocomposites are prepared via a solvent-free melt-mixing method. The effects of nano-sized BaTiO3 (nBT) on the structural, optical and thermal degradation properties of LDPE are investigated to address the qualitative interfacial interaction effects due to the spatial distribution of nBT particles in the LDPE matrix. X-ray diffraction (XRD) results confirm the uniform dispersion of nBT nano-fillers in the LDPE polymer matrix. The crystallite size of LDPE increases with increasing the nBT content. Fourier transform infrared spectroscopy (FTIR) results indicate the enhancement in interfacial physical interactions between the polymer and nano-fillers with increasing nano-filler content. The band gap energy of the nanocomposites decreases with increasing nano-filler content, which suggests chemical imperfections close to the interfaces. DSC results depict higher Tm values for the composites which is attributed to the heterogeneous nucleating effects of the nBT particles. Thermo-gravimetric analysis (TGA) results indicate an increase in the decomposition temperature (TD), thermal stability and good dispersibility probability of nBT with increasing nBT. The photocatalytic decomposition of MB is highest (73.52%) for the 10% nBT incorporated LDPE nanocomposite sample. These results correlate with the effect of the interfacial interactions between the nBT fillers and the LDPE polymer matrix. � 2023 Elsevier LtdItem Mixed-phase MoS2 nanosheets anchored carbon nanofibers for high energy symmetric supercapacitors(Elsevier Ltd, 2023-03-14T00:00:00) Kour, Pawanpreet; Deeksha; Kour, Simran; Sharma, A.L.; Yadav, KamleshMixed-phase MoS2 (MS) nanosheets anchored carbon nanofibers (CNFs) have been synthesized via a hydrothermal route. The concentration of CNFs has been varied in the MS/CNF-x composite (where, x = 1, 1.5, 2, and 3 represents the molar concentration of CNFs) to investigate the impact of CNFs on the electrochemical behavior of the material. The incorporation of CNFs offers a conductive path for the diffusion of ions and provides structural support which limits the restacking of the MoS2 layers during the charging/discharging. The MS/CNF-2 composite delivered superior electrochemical performance compared with the other composites owing to the positive synergy between MoS2 and CNFs. The specific capacitance manifested by MS/CNF-2 (626.08 F g?1 at 1 A g?1) is about four times that of pristine MS (159.35 F g?1). It is also observed that MS/CNF-2 exhibited higher electrochemical stability than pristine MS. Furthermore, the symmetric supercapacitor (SSC) device achieved a tremendous energy density of 42.6 Wh kg?1 at 2.4 kW kg?1. To test its practical applicability, LEDs of different color (red, green, and blue) have been illuminated using a series combination of three symmetric electrode cells. The red, green, and blue LEDs lighted up for 15 mins, 7 mins, and 3 mins. The results demonstrate the superiority of the MS/CNF composite for symmetric supercapacitors. � 2023Item Transition Metal-based Perovskite Oxides: Emerging Electrocatalysts for Oxygen Evolution Reaction(John Wiley and Sons Inc, 2023-01-23T00:00:00) Deeksha; Kour, Pawanpreet; Ahmed, Imtiaz; Sunny; Sharma, Surender Kumar; Yadav, Kamlesh; Mishra, Yogendra KumarDevelopment of clean and sustainable renewable energy sources is imperative to deal with the future energy crises. Various technologies have been developed in this context, for example, water electrolysis, reversible fuel cell and metal-air batteries etc. However, the sluggish kinetics of oxygen evolution reaction (OER) occurring at the anode of these energy storage/conversion systems becomes a significant hurdle. Recently, researchers utilized noble metals as electrocatalysts to enhance their efficiency still the high cost and scarcity of these materials draw the attention of researchers towards the cost-effective Perovskite oxide nanomaterials due to their extraordinary flexibility. In this review, the importance of perovskite oxide nanomaterials as electrocatalysts for OER is discussed, followed by related reaction mechanisms and series of activity descriptors. Fundamental understanding about the instrumentation, parameters and protocols for the experimental measurements including concerned issues are also summarized. Moreover, various activation strategies adopted in recent years to enhance the electrocatalytic performance of perovskite oxides are also underlined. The article concludes with an outlook of existing challenges and future scope of these materials as electrocatalysts. The challenges and prospects discussed herein may pave the ways to rationally design the highly active and stable perovskites to outperform noble metal-based OER electrocatalysts. � 2023 The Authors. ChemCatChem published by Wiley-VCH GmbH.Item Tunable dielectric and memory features of ferroelectric layered perovskite Bi4Ti3O12 nanoparticles doped nematic liquid crystal composite(Elsevier B.V., 2022-11-24T00:00:00) Anu; Varshney, Depanshu; Yadav, Kamlesh; Prakash, Jai; Meena, Harikesh; Singh, GautamHerein, we report the synthesis of ferroelectric layered perovskite Bi4Ti3O12 (BT4) nanoparticles (NPs) and the temperature-dependent dielectric and electro-optical (especially memory effect) properties of 4-pentyl-4?-cyanobiphenyl (5CB) nematic liquid crystal (NLC) doped with 1 wt% BT4 NPs (i.e. 5CB-BT4 composite) using polarising optical microscopy and frequency-dependent dielectric spectroscopy techniques. BT4 NPs were synthesised via a microwave-assisted chemical method and characterised using various instrumental techniques, which confirmed the formation of a non-stoichiometric and oxygen-deficient orthorhombic crystal phase. The agglomeration-free and uniform dispersion of BT4 NPs in the 5CB matrix was confirmed by optical textures. The optical memory studied by bias voltage-dependent (ON-OFF) optical textures is decreased by ? 2.6 times in the 5CB-BT4 composite compared with 5CB. Moreover, dielectric parameters such as dielectric permittivity, dielectric loss, loss tangent, conductivity, and activation energy of 5CB and composite (5CB-BT4) are estimated using dielectric spectroscopy. The dielectric anisotropy is decreased, whereas no shift in the clearing temperature is observed in the 5CB-BT4 composite compared to the 5CB sample. Also, the DC conductivity of 5CB-BT4 composite is found to be increased by approximately four times compared to the 5CB. Our studies clearly demonstrate the tunability of the dielectric and optical memory features of NLC (5CB) matrix by dopant BT4 NPs, without significantly affecting the molecular alignment of the NLC molecules. Such composites would certainly be useful in the fabrication of NLC based tunable devices such as optical memory and conductivity switches. � 2022 Elsevier B.V.Item Effects of Interfacial Interactions and Nanoparticle Agglomeration on the Structural, Thermal, Optical, and Dielectric Properties of Polyethylene/Cr2O3 and Polyethylene/Cr2O3/CNTs Nanocomposites(Springer, 2022-11-22T00:00:00) Gupta, Jaya; Kumar, Ajay; Roy, Ayan; Anu; Deeksha; Kour, Pawanpreet; Singh, Ravi Pratap; Yogesh, Gaurav Kumar; Yadav, KamleshIn this report, we have synthesized the binary and ternary phase nanocomposites [(polyethylene (PE)1?X/(Cr2O3)x) and (PE)1?X/(Cr2O3)X/CNTs (where X = 0,�2%, 4%, 6%, 8%, and 10%)] using the melt mixing method and studied the structural, optical, thermal and dielectric properties with an increase in Cr2O3 nanofiller concentration. Our results show an increase in interfacial interactions between Cr2O3 nanofiller and PE matrix with an increase in nanofiller concentration up to X = 6%. After that, the interactions decreased with a further increase in X because of the increase in the size of the Cr2O3 nanoparticle aggregates. Incorporating 2% carbon nanotubes (CNTs) into (PE)1?X/(Cr2O3)X nanocomposites, further decreases the interactions between the Cr2O3 nanofiller and the PE matrix. � 2022, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.Item LaCoO3Perovskite Nanoparticles Embedded in NiCo2O4Nanoflowers as Electrocatalysts for Oxygen Evolution(American Chemical Society, 2022-11-08T00:00:00) Kubba, Deeksha; Ahmed, Imtiaz; Kour, Pawanpreet; Biswas, Rathindranath; Kaur, Harpreet; Yadav, Kamlesh; Haldar, Krishna KantaIt is essential to design high-efficiency, stable, and inexpensive electrocatalysts for the oxygen evolution reaction (OER). We fabricate a hybrid system of perovskite LaCoO3 with spinel NiCo2O4 denoted LaCoO3/NiCo2O4 via an in situ hydrothermal process. In situ incorporation of LaCoO3 nanoparticles on the NiCo2O4 nanoflower surface is confirmed by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) images. Benefiting from the interface engineering, the obtained LaCoO3/NiCo2O4 hybrid nanoflowers exhibit the lowest overpotential of 353 at a current density of 10 mA/cm2 and a small Tafel slope of 59 mV/dec in alkaline media compared with pristine LaCoO3 (401 mV, 116 mV/dec) and NiCo2O4 (386 mV, 73 mV/dec). The optimized sample possesses a higher electrochemical surface of 111.45 cm2 than LaCoO3 perovskite (35.37 cm2) and NiCo2O4 spinel oxide (61.37 cm2) structures. The enhanced OER performance of the LaCoO3/NiCo2O4 composite structure is due to the accumulation of LaCoO3 nanoparticles over NiCo2O4 petals, which introduces a substantial number of electrochemically active sites for the catalysis process to promote charge and mass transport. In addition to this, LaCoO3/NiCo2O4 exhibits long-term stability over 20 h. Thus, it is believed that the excellent OER activity of the LaCoO3/NiCo2O4 composite structure is associated with strong interaction between LaCoO3 and NiCo2O4 as well as a large surface area and a unique flower structure. � 2022 American Chemical Society.Item Effect of Different Ablation Time of ns-pulsed Laser on the Synthesis of Silver Nanoparticles in Liquid(Springer Science and Business Media Deutschland GmbH, 2022-09-01T00:00:00) Paroha, Prahalad Prasad; Yogesh, Gaurav Kumar; Singh, Birendra; Yadav, Kamlesh; Tewari, AnuragIn the present report, we have studied the effect of nanosecond pulsed laser irradiation time on the particle abundance, morphology, and optical properties of silver nanoparticles (Ag-NPs). High-resolution transmission electron microscopy, selected area diffraction pattern, and UV-visible absorption spectroscopy were used to characterize morphological, structural, and optical properties of the Ag-NPs. The prolonged laser irradiation above 60�min demonstrates the melting and diffusion-induced aggregation of Ag-NPs. The statistical evaluation of various particles under different irradiation durations reveals uniform and monodispersed particle distribution for only 60�min of ablation duration. � 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.