Browsing by Author "Caglar, Basar"

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Citation - WoS: 13
Citation - Scopus: 13
Application of work function measurements in the study of surface catalyzed reactions on Rh(1 0 0)
(Taylor and Francis Ltd. michael.wagreich@univie.ac.at, 2018) Başar Ca̧ǧlar; Ali Can Kizilkaya; J. W.Hans Niemantsverdriet; C. J. Weststrate; Weststrate, C. J. (8402915800); Niemantsverdriet, J. W.; Caglar, Basar; Kizilkaya, Ali Can; Weststrated, C. J.
The present article aims to show how work function measurements (WF) can be applied in the study of elementary surface reaction steps on metallic single crystal surfaces. The work function itself can in many cases not be interpreted directly as it lacks direct information on structural and chemical nature of the surface and adsorbates but it can be a powerful tool when used together with other surface science techniques which provide information on the chemical nature of the adsorbed species. We here illustrate the usefulness of work function measurements using Rh(100) as our model catalyst. The examples presented include work function measurements during adsorption surface reaction and desorption of a variety of molecules relevant for heterogeneous catalysis. Surface coverage of adsorbates isosteric heat of adsorption and kinetic parameters for desorption desorption/decomposition temperatures of surface species different reaction regimes were determined by WF with the aid of other surface science techniques. © 2019 Elsevier B.V. All rights reserved.
Citation - WoS: 12
Citation - Scopus: 13
Effect of Aldehyde and Carboxyl Functionalities on the Surface Chemistry of Biomass-Derived Molecules
(American Chemical Society service@acs.org, 2017) Başar Ca̧ǧlar; J. W.Hans Niemantsverdriet; C. J. Weststrate; Weststrate, C.J.; Caglar, Basar; Niemantsverdriet, J.W.
The adsorption and decomposition of acetaldehyde and acetic acid were studied on Rh(100) to gain insight into the interaction of aldehyde and carboxyl groups of biomass-derived molecules with the surface. Temperature-programmed reaction spectroscopy (TPRS) was used to monitor gaseous reaction products whereas Reflection absorption infrared spectroscopy (RAIRS) was used to determine the nature of surface intermediates and reaction paths. The role of adsorbate interactions in oxygenate decomposition chemistry was also investigated by varying the surface coverage. Acetaldehyde adsorbs in an η2(C O) configuration for all coverages where the carbonyl group binds to the surface via the C and O atoms. Decomposition occurs below room temperature (180-280 K) via C-H and C-C bond breaking which releases CO H and CHx species on the surface. At low coverage CHx dehydrogenation dominates and surface carbon is produced alongside H2 and CO. At high coverage about 60% of the CHx hydrogenates to form methane whereas only 40% of the CHx decomposes further to surface carbon. Acetic acid adsorbs dissociatively on the Rh(100) surface via O-H bond scission forming a mixture of mono- and bidentate acetate. The decomposition of acetate proceeds via two different pathways: (i) deoxygenation via C-O and C-C bond scissions and (ii) decarboxylation via C-C bond scission. At low coverage the decarboxylation pathway dominates a process that occurs at slightly above room temperature (280-360 K) and produces CO2 and CHx where the latter decomposes further to surface carbon and H2. At high coverage both decarboxylation and deoxygenation occur slightly above room temperature (280-360 K). The resulting O adatoms produced in the deoxygenation path react with surface hydrogen or CO to form water and CO2 respectively. The CHx species dehydrogenate to surface carbon for all coverages. Our findings suggest that oxygenates with a C=O functionality and an alkyl end react on the Rh(100) surface to produce synthesis gas and small hydrocarbons whereas CO2 and synthesis gas are produced when oxygenates with a COOH functionality and an alkyl end react with the Rh(100) surface. For both cases carbon accumulation occurs on the surface. © 2017 Elsevier B.V. All rights reserved.
Citation - WoS: 17
Citation - Scopus: 15
Efficient synthesis of perovskite-type oxide photocathode by nonhydrolytic sol-gel method with an enhanced photoelectrochemical activity
(Elsevier Ltd, 2018) Taymaz Tabari; Mehdi Ebadi; Dheerendra Singh; Başar Ca̧ǧlar; M. Barış Yağcı; Yagci, M. Baris; Tabari, Taymaz; Ebadi, Mehdi; Singh, Dheerendra; Caglar, Basar
The photoelectrochemical activity of PbTiO3 (PTO) for water splitting was studied by linear sweeping voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) techniques. The nanohydrolytic sol-gel method was used to synthesise a crystalline PbTiO3 perovskite nanoparticles. The physical and chemical properties of nanoparticles such as crystal structure surface area reducibility band gap energy particle morphology and size surface composition and valence states were investigated by X-Ray diffraction (XRD) BET temperature-programmed reduction (TPR) UV diffuse reflectance spectroscopy (UV-DRS) high resolution scanning and transmission electron microscopy (HR-SEM and HR-TEM) along with X-Ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). PTO nanoparticles showed pure crystallinity high surface area (14 m2/g) and high oxygen mobility. PTO has band gap energy of 2.66 eV which makes it active under visible light irradiation. Moreover nanoparticles vary in size and create a core-shell structure in a way that small particles surround large particles. The core-shell structure along with a free defected sites on the surface results in high photoelectrochemical activity for water splitting reaction. The I–V curve revealed that the PTO nanoparticles are a p-type electrode with the photocurrent efficiency of ≈19%. This suggests that the photoelectrode does not require external bias to initiate the water splitting and the reaction can be initiated simply by making a connection between the anode and the cathode. In addition a great stability is observed for PTO electrodes during the reaction as evidenced by no leaching to the reaction medium. © 2020 Elsevier B.V. All rights reserved.
Citation - WoS: 4
Citation - Scopus: 5
Electrooxidation of Glycerol on Monometallic and Bimetallic Catalysts-Containing Porous Carbon Cloth Electrodes in an Alkaline Medium
(IOP Publishing Ltd, 2021) Başar Ca̧ǧlar; Youssef El Hassan; Oguzhan Basak; A. Hepbasli; Basak, Oguzhan; El Hassan, Youssef; Hepbasli, Arif; Caglar, Basar
The electrooxidation of glycerol was studied on monometallic (Pt/C Co/C Ni/C Cu/C) and bimetallic catalysts (PtCo/C PtNi/C PtCu/C) - containing porous carbon cloth electrodes in an alkaline medium to gain insight about the potentials of electrodes for simultaneous hydrogen and chemical production. Physical and chemical properties of catalysts were characterized by using X-ray diffraction X-ray photoemission spectroscopy and transmission electron microscopy while electrochemical characteristics of electrodes were investigated by cyclic voltammetry choronoamperometry and electrochemical impedance spectroscopy. Bimetallic catalysts-containing electrodes showed higher glycerol electrooxidation activities and stabilities compared to monometallic catalysts-containing electrodes. The highest activity was observed on the PtCu/C-containing electrode due to its higher electrochemical active surface area and low kinetic and mass transfer resistance. It was also found that the presence of porous carbon cloth had a considerable effect on the glycerol electrooxidation activity. © 2021 Elsevier B.V. All rights reserved.
Citation - WoS: 31
Citation - Scopus: 33
Energy and exergy analysis of a PV-T integrated ethanol PEM electrolyzer
(Elsevier Ltd, 2021) Başar Ca̧ǧlar; Mustafa Araz; Huseyin Gunhan Ozcan; Atalay Calisan; A. Hepbasli; Ozcan, Huseyin Gunhan; Calisan, Atalay; Araz, Mustafa; Hepbasli, Arif; Caglar, Basar
A photovoltaic-thermal (PV-T) integrated ethanol proton exchange membrane electrolyzer (PEME) was proposed as a low-energy consuming energy storage option for renewable-sourced electricity as well as a way for simultaneous chemical production in this study. Energy and exergy analyses were applied to each component of the system (e.g. pumps heat exchanger PV-T PEME and separation unit (SPU)) and the whole system to assess the system performance. The mathematical modelling of the whole system along with its main components except for the SPU was done using the Engineering Equation Solver (EES) software package while the SPU was modelled through the ASPEN Plus. A detailed modelling of the PEME was also included. The effects of the PV-T and PEME parameters on energy and exergy efficiencies of the system were evaluated while the improvement potentials and scale up options were discussed. Energy and exergy efficiencies of the proposed system at the optimum operation of the PEME and under average climatic conditions in the city of Izmir Turkey were determined to be 27.8% and 3.1% respectively. Energy and exergy efficiencies of the system were mainly regulated by the PV-T and PEME whose energy and exergy efficiencies were 40.6% 56.6% and 13.8% 14.1% respectively. Effective PEME parameters for energy and exergy efficiencies of the system were membrane conductivity membrane thickness anode catalyst and the operation temperature of the PEME. By changing the PV-T and PEME parameters and by scale-up energy and exergy efficiencies of the system could be improved. © 2021 Elsevier B.V. All rights reserved.
Citation - WoS: 33
Citation - Scopus: 32
Microwave assisted synthesis of La1 - xCaxMnO3 (x=0- 0.2 and 0.4): Structural and capacitance properties
(ELSEVIER SCI LTD, 2017) Taymaz Tabari; Dheerendra Singh; Atalay Calisan; Mehdi Ebadi; Haman Tavakkoli; Basar Caglar; Calisan, Atalay; Tavakkoli, Haman; Tabari, Taymaz; Ebadi, Mehdi; Caglar, Basar; Singh, Dheerendra
The effect of calcium incorporation on the physicochemical and electrochemical properties of the LaMnO3 (LM) perovskites was studied via several techniques. Moreover a new microwave assisted method was used to synthesize La(1-x)Ca()M(x)nO(3)(LCM) perovskites with various calcium content (x = 0.2 and 0.4). Then the physicochemical properties of the materials such as crystal structure particle size surface area reducibility and band gap energy were investigated by X-ray Diffraction (XRD) High resolution Scanning and Transmission Electron Microscope (HR-SEM and HR-TEM) BET analysis Temperature-programmed Reduction (TPR) and UV-visible Diffuse Reflectance Spectroscopy (UV-VIS DRS). The increase in partial concentration of calcium resulted in a high specific surface area larger particle size and an enhanced reducibility along with an increase in the band gap energy. In addition cyclic voltammetry was applied to LM and LCM perovskites to determine the effect of calcium incorporation on the capacitance of the electrochemical cell. It showed that the capacitance decreases with the amount of Ca2+ incorporated into the LM structure. This effect is linked to the formation of Mn4+ which hinders the electron transfer in the structure. The decline in the charge transfer is revealed by the specific capacitance. Finally our findings showed that the microwave assisted method provides a green efficient and time-saving route for perovskite synthesis and the calcium incorporation induces a negative effect on the capacitance properties of the LM perovskites.
Citation - WoS: 9
Citation - Scopus: 11
Modelling and analysis of heat pump integrated Photovoltaics-Wind systems for an agricultural greenhouse in Turkey
(Elsevier Ltd, 2024) Zeynep Özcan; Levent Bilir; Başar Ca̧ǧlar; Bilir, Levent; Caglar, Basar; Ozcan, Zeynep
This study focused on modelling and analysing photovoltaics and wind systems to meet the heating demand of a commercial greenhouse. The aim is to evaluate technical economic and environmental performances of the related systems and to determine the optimum configuration. A novel approach was introduced by integrating hybrid energy systems with large-scale wind turbines and developing a dynamic heat transfer model. A large commercial greenhouse with an area of 26640 m2 located in Izmir Turkey was selected for considering Mediterranean climate and a detailed heat transfer model of the greenhouse were developed considering heat transfers by convection radiation ventilation and infiltration. A combination of air source heat pumps photovoltaic panels and wind turbines were used for meeting the heating demand of the related greenhouse. Five different on-grid energy systems scenarios namely (i) Photovoltaics-Heat Pump (ii) Photovoltaics-Wind Turbine- Heat Pump (iii) Wind Turbine- Photovoltaics- Heat Pump (iv) Wind Turbine- Heat Pump and (v) only Heat Pump were considered. The system modelling with a detailed heat transfer analysis of the greenhouse was made by MATLAB. The energy analysis of the systems was performed on an hourly basis for one calendar year. The annual heating demand and the corresponding electricity consumption of the greenhouse were calculated as 497.37 and 114.07 kWh/m2 respectively. Net Present Value Levelized Cost of Energy and CO2 savings were used to evaluate economic and environmental performances of the systems. Among five on-grid energy system scenarios the first scenario consisting of 5271 photovoltaic panels and 20 heat pumps emerged as the most economically attractive choice with Net Present Value and Levelized Cost of Energy of $547440.40 and 0.080146 $/kWh respectively. Critical parameters affecting the economy of this scenario were found to be electricity prices tomato yield and photovoltaic panel prices. For environmental evaluation the fourth scenario integrating wind turbines and heat pumps achieves the highest CO2 savings of 2064.73 tons due to increased renewable electricity production and lower life-cycle CO2 emissions of wind turbines compared to photovoltaic systems. This analysis enhanced the understanding of energy dynamics in greenhouse environments contributing to the advancement of sustainable practices in agriculture. © 2024 Elsevier B.V. All rights reserved.
Citation - WoS: 22
Citation - Scopus: 23
Multiparameter-based product energy and exergy optimizations for biomass gasification
(Elsevier Ltd, 2021) Başar Ca̧ǧlar; Duygu Tavsanci; Emrah Biyik; Caglar, Basar; Tavsanci, Duygu; Biyik, Emrah
The thermodynamic modelling of biomass gasification was studied by using Gibbs free energy minimization approach. Different from the studies using the same approach the simultaneous presence of all gasifying agents (air H2O and CO2) was considered and a multiparameter optimization was applied to determine the synergetic effect of gasifying agents for hydrogen syngas with a specific H2/CO ratio and methane production. The performance of gasification was assessed by using technical and environmental performance indicators such as product yields cold gas efficiency exergy efficiency CO2 emission and the heat requirement of the gasifier. The results show that the simultaneous presence of gasifying agents does not create considerable changes in syngas yield H2 yield methane yield CGE and exergy efficiency while it allows to tune the H2/CO ratio and the heat requirement of the gasifier. The highest syngas yield is observed at T > 1100 K and 1 bar and when SBR > 0.5 and/or CBR > 0.8 with the absence of air at which CGE changes between 114% and 122% while exergy efficiency is between 77% and 86%. The results prove that CO2 offers several advantages as a gasifying agent and suggests that CO2 recycling from gasifier outlet is a useful option for the biomass gasification. © 2021 Elsevier B.V. All rights reserved.
Citation - WoS: 15
Citation - Scopus: 16
Proposal of novel exergy-based sustainability indices and case study for a biomass gasification combine cycle integrated with liquid metal magnetohydrodynamics
(Institution of Chemical Engineers, 2023) Demet Canpolat Tosun; Emin Açıkkalp; Başar Ca̧ǧlar; Onder Altuntas; A. Hepbasli; Altuntas, Onder; Açıkkalp, Emin; Tosun, Demet Canpolat; Hepbasli, Arif; Caglar, Basar
Exergy is considered a way to sustainability. Exergy-based analyses have been recently widely used for performance assessment and comparison purposes of energy systems from production to end-user while different sustainability related indices or indicators including exergetic concepts have been developed in the literature. In this regard the present study proposed five different indices: (i) Exergetic Fuel Based Environmental Remediation Index (χ) (ii) Exergetic Product Based Environmental Remediation Index (δ) (iii) Exergetic Fuel Based Total Environmental Remediation Index (β) (iv) Exergetic Product Based Total Environmental Remediation Index (α) and (v) Improved Sustainability Index (ISI). These indices were applied to a novel Biomass-integrated Gasification Combine Cycle (BIGCC) integrated with Liquid Metal Magnetohydrodynamics (LMMHD). They allowed to perform a more complete environmental analysis by considering the exergetic cost of environmental remediation of the process. The average exergy efficiency values for the BIGCC LMMHD and the overall system were determined as 0.491 0.222 and 0.688 under daily ambient temperatures for a year and different air to fuel ratio (AFR) conditions respectively. The average values for χ β δ α and ISI were 1.636 2.389 1.949 2.848 and 0.513 respectively. © 2023 Elsevier B.V. All rights reserved.