Yazar "Karabulut, Ezman" seçeneğine göre listele

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    Catalytic dehydrogenation efficiency of carbon quantum supported Ni nanoparticles and synthesized via dimethylformamide (DMF)
    (Pergamon-Elsevier Science Ltd, 2026) Izgi, Mehmet Sait; Onat, Erhan; Faal, Sultan; Celik, Fatih Ahmet; Sahin, Omer; Karabulut, Ezman
    In this study, carbon quantum dot catalysis Ni@MOFCQDs synthesized via dimethylformamide (DMF) and urea molecules supported by nickel metal, was designed both theoretically and experimentally. Borane Dimethylamine Complex (DMAB) and Sodium Borohydride (SBH) were used to evaluate the dehydrogenation performance of this catalysis. The Ni@MOFCQDs nanocatalyst development stages were characterized using some analytical methods, and was theoretically optimized under the non-self-consistent GFN1xTB (Geometries, Frequencies, and Non-covalent interactions Tight Binding). At the same time the dehydrogenation kinetics of hydrogen sources in the Ni@MOFCQDs were investigated by using the optimum amount of sodium hydroxide, catalyst amounts, substrate concentration. The dehydration rates of SBH and DMAB in Ni@MOFCQDs nanocatalyst are measured as 1542 and 862 mL/g.min, respectively. Theoretically, the formation of Ni@MOFCQDs in CQDs synthesized in DMF is found to be 30 % more efficient in both SBH and DMAB hydrolyses when comparing to Ni@CQDs synthesized in water. So it is seen that SBH hydrolysis is 150 % more efficient than DMAB hydrolysis in both Ni@CQD and Ni@MOFCQDs catalysis. Ni-centered stabilization of organic small molecules with C-N single bonds was found to exhibit good dehydrogenation performance. It is clear that increasing the number of C-N molecules in electrostatically active area of the transition metal's d orbital supports catalytic performance.
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    Computational study on a cobalt-based complex compound with amine ligand in X-doped (X = Co, Ru, Rh) Ca12Al14O33 functional material as an innovative catalyst by NaBH4 hydrolysis for determining hydrogen generation process
    (Pergamon-Elsevier Science Ltd, 2024) Celik, Fatih Ahmet; Karabulut, Ezman; Izgi, Mehmet Sait; Yilmaz, Mucahit; Onat, Erhan
    Sodium borohydride (NaBH4) has been generally studied as a source of hydrogen (H2) due to its important advantages with the development of support materials and catalysts for H2 release in the energy sector. In this context, we carry out molecular dynamics (MD) simulations by using extended tight-binding (xTB) model Hamiltonian based on density functional theory (DFT) and analyze the Ca12Al14O33 functional material doped X metals (X = Co, Ru, Rh) as a catalyst with [Co(III)(N3)3(C9H8N2)2] as complex compound with amine ligand from NaBH4 hydrolysis for H2 production. The use of a functional material doped by X metals causes to the high rate in H2 production when compared to without functional material doped by X metals. The increase of complex compound with amine ligand facilitates H2 production. Rh on the functional material displays the best catalytic performance compared to Ru and Co to increase the H2 production rate. Also, the increment of temperature has a positive effect on the H2 production rate with functional material doped Co, Ru and Rh metals. Thus, Ca12Al14O33 support material doped with noble metals appears promising as an innovative catalyst for H2 production.
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    Experimental and Theoretical Investigation of Ammonia Borane Dehydrogenation Using an Aniline-Enhanced Ru Nanocatalyst
    (Wiley-V C H Verlag Gmbh, 2026) Izgi, Mehmet Sait; Sahin, Omer; Onat, Erhan; Enisoglu, Muhammed; Celik, Fatih Ahmet; Karabulut, Ezman
    This study aimed to synthesize carbon quantum dots (CQDs) through the interaction of carboxyl (-COOH) and amino (-NH2) groups and to investigate experimentally and theoretically hydrogen (H2) production efficiency from ammonia borane (AB) hydrogen source using this CQDs structure with ruthenium (Ru) catalyst support material. CQDs were obtained by the hydrothermal method from aniline (A) and trichloroacetic acid (TCA) under weak base-acid coupling. A heterogeneous Ru@ATCA catalyst is developed using Ru metal nanoclusters decorated on CQDs. The development process is characterized by advanced analytical methods (UV, PL, BET, ICP-OES, TEM, XPS, XRD). As a result of the AB catalytic reaction at 298 K, a very high Hydrogen Production Rate (HGR) of 102.1 L/g.min and a catalyst cycle frequency (TOF) of 356 min-1 are obtained. The reaction proceeds in a first-order manner, with activation energy (Ea) of 22.3 kJ/mol, activation enthalpy and entropy of 19.65 and -29.95 J/mol, respectively. The mesoporous structures under this interaction, the increase in active surface area increases H2 production efficiency by providing lower viscosity for both AB hydrolysis and the surrounding molecular groups. The H2 production efficiency is compared with GFN1xTB modeling. According to modeling, the Ru activity of the weak acid TCA alone has a weaker catalytic effect than the Ru activity resulting from its interaction with the weak base aniline molecule, demonstrating the importance of the weak acid and weak base interactions.
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    H2 2 production from ammonia borane hydrolysis with catalyst effect of Titriplex® ® III carbon quantum dots supported by ruthenium under different reactant Conditions: Experimental study and predictions with molecular modelling
    (Elsevier Science Sa, 2024) Onat, Erhan; Celik, Fatih Ahmet; Sahin, Omer; Karabulut, Ezman; Izgi, Mehmet Sait
    This study presents experimental and theoretical results on the role of the catalytic effect by ruthenium added titriplex (R) (R) III Carbon Quantum Dots (CQD) support material in the hydrolysis of ammonia borane for H2 2 duction. H2 2 production was achieved under different reactant conditions (in variable amounts of catalysis, ruthenium, NaOH, ammonia borane and at various temperature). Since the experimental results and theoretical calculations which includes the effect of all electrical forces acting on valence electrons (overlap density tions, van der Waals forces, Covalent bonding and halogen bonds) are in very good agreement in the study, theoretical predictions are also made. By considering the rhodium element instead of the ruthenium element, performance of the titriplex support material was estimated to be approximately 30% more effective ruthenium. The NaOH molecule acts as a hydrolyzed water molecule with catalysis interaction and contributes the formation of oxidized boron. When NaOH is not present, the interaction time of the ammonia borane molecule with catalysis comes to the fore. This time is called threshold time. In molecular modeling, while almost all of the ammonia borane molecules contribute to H production, only 15% of the water molecules contribute this rate. However, while some of the released H atoms remains in the water, other parts observe to play a role the production of H2 2 and hydronium. The interaction rate of the water molecule increases with the increase the interaction surface of the catalyst. Any external effect that prevents the formation of hydronium and celerates the interaction of free H atoms with each other increases the efficiency. One of the predicted results this study is that the increased pressure shows separating role for hydronium.
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    High availability and outstanding catalytic activity in sodium borohydride hydrolytic dehydrogenation of CQD/GO@Co catalyst by green synthesis: Experimental and computational perspective
    (Pergamon-Elsevier Science Ltd, 2024) Onat, Erhan; Celik, Fatih Ahmet; Karabulut, Ezman; Izgi, Mehmet Sait
    This study is a pioneering study that experimentally and theoretically measures the effect of heterogeneous catalyst structure on hydrogen production. In this research, the catalytic activity of the (CQD/GO@Co) catalyst, which was formed by doping Co onto the synthesized graphene oxide (GO) on carbon quantum dots (CQD) obtained from caffeine by green synthesis, was investigated. The catalyst CQD/GO@Co was synthesized with high dispersibility and activity, and it was successfully employed in the hydrolysis of NaBH4 for the first time. The effective catalytic compatibility of caffeine and cobalt element increased approximately 3 times on the GO layer. In order to determine the most effective catalyst conditions in the study, NaOH concentration, catalyst amount, NaBH4 amount and temperature were tested under different reactant conditions. The catalyst was characterized using X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Brunauer-Emmett-Teller (BET) analyses. Field emission scanning electron micrographs (FESEM) were taken by Field emission scanning electron microscope (Zeiss, Sigma). Energy dispersive X-ray (EDX) spectra were obtained from Energy dispersive X-ray spectroscope. According to spherical aberration transmission electron microscopy studies, the uniform dispersion of Co nanoparticles (average diameter: +/- 3,1 nm) on CQDs, as well as the very small size and good dispersion of Cobalt (Co), are conducive to improved catalytic performance. This situation was determined by molecular modeling with the Non-scc GFN1xTB model and results supporting the experimental data were obtained. The maximum hydrogen production rate with sodium borohydride hydrolysis using cobalt-based catalyst increased approximately 32 times (from metallic crystal form of Co catalyst 2860 mL/min.(g.cat) to the present form 49,044 mL/min.(g.cat). The activation energy, activation enthalpy, and activation entropy of the Co@CQDs catalyst were founded to be 20.65 kJ mol(-1), 2.64 kJ mol(-1), and -108,97 J mol(-1), respectively.
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    Hydrogen production mechanism and catalytic productivity of Ni-X@g-C3N4 (X = precious and non-precious promoter metals) catalysts from KBH4 hydrolysis under stress loading and atmospheric pressure: Experimental analysis and molecular dynamics approach
    (Elsevier Science Sa, 2024) Celik, Fatih Ahmet; Aygun, Murat; Karabulut, Ezman; Onat, Erhan; Izgi, Mehmet Sait; Yilmaz, Muecahit; Ayguen, Zeynep
    In this study, the pressure effect of Ni-based catalysts added a second promoter metal to increase of catalyst performance supported a graphite carbon nitride (g-C3N4) monolayer on hydrogen release mechanisms from potassium boron hydride (KBH4) hydrolysis was investigated using molecular dynamics (MD) method based on tight-binding density functional theory (DFT). The use of the various promoters, such as transition metals (X = Cu, Ta and W) and noble metals (X = Pd, Pt and Rh) with applying a high external pressure was investigated to understand the role on catalytic performance of the Ni-based catalysts under stress loading. The g-C3N4 monolayer doped with Ni-X nano-catalysts was used for efficient H-2 release from KBH4 hydrolysis. The computational results show that the number of H-2 shows more increment with MD time for NiW and NiRh catalysts than other NiTa and NiCu (transition metals) and NiPd and NiPt (noble metals) under 0 GPa pressure. On the other hand, a notable increase in H-2 amount is seen only NiCu and NiRh catalysts under 50 GPa. Also, the mechanism of the H-2 production reaction from KBH4 hydrolysis of g-C3N4 doped NiCo catalysts was clarified. High-performance cost metal catalysts such as NiCo was investigated as both experimentally and modeling under atmospheric pressure to enhance its commercial application value. Some experimental applications and analyzes were also performed to measure the accuracy of the modeling for the relevant molecular groups in the system.
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    Molecular dynamics approach to efficient hydrogen generation process of Co-B catalysts decorating lanthanides (La, Ce, Pr, Nd) supported by flat-sheet and twisted ThMoB4-type graphene from NaBH4 hydrolysis: Insights from non-self-consistent GFN1-xTB method
    (Elsevier Science Sa, 2024) Celik, Fatih Ahmet; Karabulut, Ezman; Onat, Erhan; Izgi, Mehmet Sait; Yilmaz, Mucahit
    In this study, the promoter role on highly efficient hydrogen generation productivity and H-2 formation mechanisms of Co-B-X catalysts modified by rare earths (X = La, Ce, Pr, Nd) supported by flat-sheet and twisted ThMoB4-type graphene from sodium borohydride (NaBH4) hydrolysis was investigated using molecular dynamics (MD) method based on non-self-consistent tight binding GFN1-xTB Method. The twisted ThMoB4-type graphene layer was constructed by adsorbing of ethylene carbonate (EC) molecule on armchair site of graphene surface with applying of geometric optimization process. The addition of Nd to CoB exhibited to higher H-2 release compared to other CoB containing lanthanides (La, Ce and Pr) both flat-sheet and twisted ThMoB4-type graphene. While the number of H-2 for Co-B-Nd is 14, the H-2 amount is only 8 for Co-B-Ce supported flat-sheet graphene at the end of simulation time. Also, the placing of twisted graphene instead of flat-sheet in the catalytic complex led to about 36 % increase in H-2 number for Co-B-Nd. The computational results revealed that the availability of the active sites, such as basicity of catalytic environment related to OH and H species and the mobility of Co atom, played an important role for catalytic activity and performance for H-2 production. This work can provide new insight for experimental studies of Co-B-X (X = La, Ce, Pr, Nd) catalysts for hydrogen production in atomic-level and the creation of new hydrogen energy applications and facilitates for H-2 generation efficiency.
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    Reaction pathways and hydrogen production via ethanolysis, methanolysis and hydrolysis reactions of sodium borohydride by using p-tert-butylcalix[4]arene complexes: molecular dynamics study
    (Springer, 2026) Celik, Fatih Ahmet; Karabulut, Ezman; Sahin, Omer; Izgi, Mehmet Sait; Onat, Erhan
    Here we employed extended tight-binding DFT based molecular dynamics (MD) simulations to investigate the dehydrogenation reaction mechanisms of sodium borohydride (NaBH4) supported X metal-doped p-tert-butylcalix[4]arene (X = Ni, Co, Ru and Pd) complexes (Calixarene(4)-Cplx) in water, methanol (MeOH) and ethanol (EtOH) environments. Also, for the performance of nano-catalyst systems through NaBH4 hydrolysis, methanolysis and ethanolysis was investigated. A key finding is that the interaction of the metal atom and hydroxyl molecular groups in the catalyst with the hydroxyl groups in MeOH and EtOH molecules creates metastable hydrogen bonds in the system. In this case, the dehydrogenation reaction appears to accelerate. However, for stability, this hydrogen bonding must be eliminated. This requires additional barrier energy for the catalyst to stabilize. This state makes the rate of H2 formation slows down. When Co, Ni Pd and Ru- Calixarene(4)-Cplx are dropped into water instead of ethanol, the increase in H2 amount occur as 35%, 78.57%, 113.2% and 53.33%. It has been determined that when X metal interpenetrate into Calixarene(4)-Cplx are used, hydrolysis and methanolysis of NaBH4 exhibit higher H2 evaluation than NaBH4 ethanolysis. Moreover, the better H2 production rate (2.6 times more) is observed in supported catalysts compared to non-supported catalyst.
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    The effect of trichloroacetic acid molecule-derived carbon quantum dot-doped ru nanoclusters on ammonia borane dehydrogenation: Experimental and density functional tight binding model
    (Elsevier, 2026) Izgi, Mehmet Sait; Onat, Erhan; Enisoglu, Muhammed; Celik, Fatih Ahmet; Karabulut, Ezman; Sahin, Omer; Demirci, Sevilay
    Developments in Ammonia borane (AB) dehydrogenation are parallel with the design of sustainable, inexpensive and high-activity catalysts. In this study, a useful and active catalyst was synthesized from Ru nanoparticles dispersed on CQD support materials obtained from trichloroacetic acid (TCA) via the hydrothermal method. Various characterization techniques (UV-PL, BET, XRD TEM and XPS) were used to explain the structure and the formation process of catalysis. In addition, the amounts of Ru loading, NaOH, catalyst and AB substrates were investigated to understand the efficiency of dehydrogenation. The stability and reusability of the synthesized Ru@CQD-TCA catalyst were tested. Here, it is observed that the catalyst is 100 % efficient after the 6th use. Moreover, its activity does not decrease much and there is no obvious agglomeration. The TOF value of the obtained Ru@CQD-TCA catalyst at 298 oK is determined as 193 (min-1) and It has a low activation energy with an energy of 39.26 kJ/mol. The stability of TCA-Ru-AB and undesirable Ru-Ru interactions are confirmed in molecular dynamics simulation. It was observed that CQD structures prepared under the interaction of small volume organic molecules with transition metals can exhibit high H2 production and high stability.