Faculty Publications
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Item RGO/ZnWO4/Fe3O4 nanocomposite as an efficient electrocatalyst for oxygen reduction reaction(Elsevier B.V., 2017) Mohamed, M.; Mutyala, S.; Mathiyarasu, J.; Bhat, D.K.Development of low cost, environmental friendly and noble metal free catalyst materials with excellent performance is essential for commercialization. In fact, this is the need of the day too. Herein, we report a facile microwave irradiation method for the synthesis of novel RGO/ZnWO4/Fe3O4 cathode catalysts for the oxygen reduction reaction (ORR) in alkaline medium. The structural and morphological features of synthesized materials are fully examined using transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM). The chemical composition and elemental analysis of the catalyst is investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy techniques. Efficiency of RGO/ZnWO4/Fe3O4 catalyst material for oxygen reduction reaction (ORR) in 0.1 M KOH is reported. The activity of catalyst is determined by linear sweep voltammogram (LSV) and rotating disk electrode (RDE) measurements in O2 saturated 0.1 M KOH electrolyte. RGO/ZnWO4/Fe3O4 catalyst exhibits higher ORR activity than RGO, ZnWO4, RGO/ZnWO4 and its electrocatalytic performance is comparable to Pt/C material and is superior to it in stability and methanol tolerance. Further, it is determined that process follows a direct four electron reaction pathway. These combined results strongly signpost that RGO/ZnWO4/Fe3O4 composite can function as an economic noble metal free ORR cathode catalyst for energy applications. © 2017 Elsevier B.V.Item Structure-sensitive electrocatalytic reduction of co2 to methanol over carbon-supported intermetallic ptzn nano-alloys(American Chemical Society service@acs.org, 2020) Payra, S.; Shenoy, S.; Chakraborty, C.; Tarafder, K.; Roy, S.The electrochemical reduction of CO2 (CO2RR) to produce valuable synthetic fuel like CH3OH not only mitigates the accumulated greenhouse gas from the environment but is also a promising direction toward attenuating our continuous reliance on fossil fuels. However, CO2RR to yield CH3OH suffers because of large overpotential, competitive H2 evolution reaction (HER), and poor product selectivity. In this regard, intermetallic alloy catalysts open up a wide possibility of fine-tuning the electronic property and attain appropriate structures that facilitate selective CO2RR. Here, we report for the first time the CO2RR over carbon-supported PtZn nano-alloys and probed the crucial role of structures and interfaces as active sites. PtZn/C, Pt3Zn/C, and PtxZn/C (1 < x < 3) synthesized from the metal-organic framework material were characterized structurally and morphologically. The catalysts demonstrated structure dependency toward CH3OH selectivity, as the mixed-phase PtxZn/C outperformed the phase-pure PtZn/C and Pt3Zn/C. The structure-dependent reaction mechanism and the kinetics were elucidated over the synthesized catalysts with the help of detail experiments and associated density functional theory calculations. Results showed that in spite of low electrochemically active surface area, PtxZn could not only have facilitated the single electron transfer to adsorbed CO2 but also showed better binding of the intermediate CO2 •- over its surface. Moreover, the lower bond energy between the mixed-phase surface and -OCH3 compared to the phase-pure catalysts has enabled higher CH3OH selectivity over PtxZn. This work opens a wide possibility of studying the role of interfaces between phase-pure nano-alloys toward CO2RR. © 2020 American Chemical SocietyItem Numerical investigation on the improved reactant mass transport with depth-dependent flow fields in polymer electrolyte fuel cell under inhomogeneous gas diffusion layer compression(Elsevier Ltd, 2021) Padavu, P.; Koorata, P.K.; Bhat, S.D.In this work, a numerical model is developed to analyse the effects of depth-dependent reactant flow field geometry under inhomogeneous gas diffusion layer (GDL) compression on the mass transport process and performance of polymer electrolyte fuel cell (PEFC). The types of depth-dependent flow channels considered in this study are: converging channel (depth continuously decreasing) and diverging channel (depth continuously increasing), and the conventional flow field designs. The model is investigated for local and global inhomogeneity due to GDL compression. The localized inhomogeneity is introduced in the flow-field rib as well as channel regions. The results are compared for reactant concentration, water concentration, local current density, and the polarization curve for different flow channel combinations. It is observed that the availability of reactants is higher in case of converging channel design, which leads to an increase in cell performance at higher currents. However, this is subjected to GDL inhomogeneity in compression. We observe in this study that such inhomogeneity, instead of having a significant impact on cell performance, lead to minimal influence in terms of reduction in cell performance. This we observe is due to improved H2 availability at anode and reduced O2 distribution at cathode that ultimately impacts respective hydrogen oxidation reaction (HOR) and reduction in oxygen reduction reaction (ORR). This study aims to investigate the cases for altered variation in cell performance due to change in depth-dependent flow fields. © 2021Item Photo- and Electrocatalytic Reduction of CO2 over Metal-Organic Frameworks and Their Derived Oxides: A Correlation of the Reaction Mechanism with the Electronic Structure(American Chemical Society, 2022) Payra, S.; Ray, S.; Sharma, R.; Tarafder, K.; Mohanty, P.; Roy, S.A Ce/Ti-based bimetallic 2-aminoterephthalate metal-organic framework (MOF) was synthesized and evaluated for photocatalytic reduction of CO2 in comparison with an isoreticular pristine monometallic Ce-terephthalate MOF. Owing to highly selective CO2 adsorption capability, optimized band gaps, higher flux of photogenerated electron-hole pairs, and a lower rate of recombination, this material exhibited better photocatalytic reduction of CO2 and lower hydrogen evolution compared to Ce-terephthalate. Thorough probing of the surface and electronic structure inferred that the reducibility of Ce4+ to Ce3+ was due to the introduction of an amine functional group into the linker, and low-lying Ti(3d) orbitals in Ce/Ti-2-aminoterephthalate facilitated the photoreduction reaction. Both the MOFs were calcined to their respective oxides of Ce1-xTixO2 and CeO2, and the electrocatalytic reduction of CO2 was performed over the oxidic materials. In contrast to the photocatalytic reaction mechanism, the lattice substitution of Ti in the CeO2 fluorite cubic structure showed a better hydrogen evolution reaction and consequently, poorer electroreduction of CO2 compared to pristine CeO2. Density functional theory calculations of the competitive hydrogen evolution reaction on the MOF and the oxide surfaces corroborated the experimental findings. © 2022 American Chemical Society.Item Unprecedented Electroreduction of CO2over Metal Organic Framework-Derived Intermetallic Nano-Alloy Cu0.85Ni0.15/C(American Chemical Society, 2022) Payra, S.; Devaraj, N.; Tarafder, K.; Roy, S.Designing suitable catalysts for efficient and selective electrocatalytic reduction of CO2 is a need of the hour, and in this regard, the well-defined, highly dispersed active metal centers can be a trendsetting research endeavor toward CO2 electroreduction due to the maximum atom utilization and unique electronic structure. This study describes the synthesis and electrocatalytic CO2 reduction activity of atomistically dispersed Cu/C and Ni/C and the intermetallic nano-alloy Cu0.85 Ni0.15 /C. The catalysts were synthesized from the corresponding MOF precursors. The successful synthesis of the monometallic and intermetallic nano-alloys was established from structural, surface morphological, and electronic properties. Cu0.85 Ni0.15 /C exhibited an unprecedented electrocatalytic reduction of CO2 with a high selectivity and high faradaic efficiency toward CH3 OH. The kinetic studies and the first-principles calculations elucidated the intricate mechanism and the superior activity of electrocatalytic reduction of CO2 over the intermetallic Cu0.85 Ni0.15 /C catalyst. © 2022 American Chemical Society. All rights reserved.Item Evaluating the PEM fuel cell performance under accelerated creep of sealants(Elsevier Ltd, 2025) Kumar, V.; Koorata, P.K.The physical properties of sealants could be crucial in affecting the performance and longevity of the polymer electrolyte membrane fuel cell (PEMFC). As the sealants' physical properties are temperature and stress-dependent due to their inherent viscoelasticity, their creep response must be explored. The numerical study presented in this article emphasizes evaluating the performance of low-temperature PEMFC (LT-PEMFC) influenced by polytetrafluoroethylene (PTFE) sealants' accelerated creep characterized by the compliance curves (MC-65). The performance of a 3D single-channel PEMFC model is investigated and compared for two cases, wherein the first case focused on PEMFC performance without sealant creep, and the second case incorporated sealants' accelerated creep to assess PEMFC performance. The detailed observation of reactant transport characteristics demonstrates that there is a substantial decline in oxygen reduction reaction (ORR) at the cathode gas diffusion layer (GDL) and cathode catalyst layer (CL) in the case of sealants' accelerated creep. Further, liquid saturation at the cathode GDL is observed to increase significantly, leading to a reduction in the performance of the cell. It is further conveyed that the current density for case 1 (without creep) and case 2 (sealants' accelerated creep) are 1.309655 and 1.041806 Acm?2, respectively, at a cell voltage of 0.4 V. The present study, therefore, addresses the viable interaction between fuel cell performance and the sealants’ accelerated creep characteristics. © 2025 Hydrogen Energy Publications LLCItem Synthesis and characterization of N-doped reduced graphene oxide for the supercapacitor application(Springer, 2025) Moodakare, R.; Sahoo, B.; Bharadishettar, N.; Rahman, M.R.; Muhiuddin, M.; Udaya Bhat, K.In this work, N-rGO is synthesized as a material for the electrode of supercapacitors using a single-stage hydrothermal process. Ammonia functions as a nitrogen source and a reducing agent, significantly enhancing its electrochemical properties. X-ray diffractometry (XRD), Raman spectroscopy, field emission gun scanning electron microscopy (FESEM), and FT-IR (Fourier-transform infrared spectroscopy) were employed for characterization of as-prepared N-rGO electrodes. The XRD plot evidences the successful reduction of as-received GO to as-prepared N-rGO. The FESEM micrograph displays the formation of highly porous and multi-layered N-rGO, showcasing significant structural characteristics. The nitrogen atoms are successfully incorporated into the resulting material (N-rGO) and have been verified through EDS and FT-IR spectroscopy studies. The specific capacitance of N-rGO reaches 107 Fg?1 at 0.5 Ag?1 in a 0.5 M H2SO4 aqueous electrolyte solution. The electrodes showed exceptional cyclic performance, maintaining approximately 130% capacitance after 10,000 cycles and delivering steady Coulombic efficiency. The material's porous structure and nitrogen doping create abundant active sites, facilitating electrolyte ion migration and producing exceptional capacitive performance. The electrochemical impedance spectroscopy study revealed that the N-rGO exhibited a distinctive capacitive behavior. The synthesized N-rGO offers excellent potential for an efficient energy storage application due to its simple, cost-effective, and eco-friendly approach. © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2025.Item CO2 concentration effects on CO2/H2O co-electrolysis in a solid oxide electrolysis button cell(Springer Science and Business Media Deutschland GmbH, 2025) Shirasangi, R.; Prasad Dasari, H.P.; Saidutta, M.B.Abstract: The influence of CO2 gas concentration on the co-electrolysis performance of an electrolyte-supported button cell (NiO-YSZ/NiO-SDC/ScSZ/LSCF-GDC/LSCF) was investigated. At 800 oC/1.5V, the interfacial polarization resistance (Rp) values for 10%CO2/15%H2O and 30%CO2/15%H2O are 7.19 and 26.91 ?.cm2, respectively. CO2 gas concentration significantly affects the Rp value. Gas diffusion resistance is dominant in the overall polarization resistance. As the CO2 concentration increases (10%?30%), H2 consumption increases, indicating RWGS dominance. For 30% CO2/15% H2O, CO2 out is slightly more than the input value due to the WGS and Boudouard reactions. As the applied voltage value increases from OCV, the H2 residue increases. H2O and CO2 co-electrolysis occurs at 1.5 V. The post-test XRD and Raman spectra results show NiO reduction and metallic Ni appearance. The post-test FE-SEM micrographs show no delamination at the air electrode/electrolyte interface, and carbon deposition is observed in the composite fuel electrode layer. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2025.