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Effective and environmentally friendly Co nanocatalyst on sodium borohydride hydrolysis in different solvents
(Elsevier BV, 2025-01) Erhan Onat; Selma Ekinci; Ömer Şahin; Mehmet Sait İzgi
This study investigates the development and performance of a cobalt (Co) nanocatalyst supported by carbon quantum dots (CQDs) for hydrogen production via sodium borohydride (NaBH₄) hydrolysis. The CQDs were synthesized using a hydrothermal method from caffeine and subsequently used to support the cobalt catalyst. The structure and properties of the synthesized catalyst were characterized using techniques such as X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and energy dispersive spectroscopy (EDX). The catalytic performance was evaluated in various solvents, with the highest hydrogen production rate observed in ethanol. The optimal conditions for Co@CQDs catalyst synthesis were identified as an 8-h hydrothermal treatment with a 3 mmol metal loading. The catalyst demonstrated excellent reusability, maintaining 100% hydrogen production efficiency after seven cycles. The activation energy for the hydrolysis reaction was found to be lower for catalysts synthesized in ethanol (25.48 kJ mol−1) compared to those synthesized in water (35.57 kJ mol−1), indicating enhanced catalytic activity. Under optimum conditions, the hydrolysis reaction in the presence of Co@CQDs (water) catalyst produced 23753 mL min−1 g−1 of hydrogen, while the hydrolysis reaction in the presence of Co@CQDs (ethanol) catalyst produced 28751 mL min−1 g−1. This study highlights the potential of CQDs-supported Co nanocatalysts for efficient and sustainable hydrogen production.
Eco-friendly biosynthesized silver, copper, and nickel nanoparticles mediated Rheum ribes: Assessment of their cytotoxicity and antimicrobial activity
(Elsevier BV, 2025-02) Bahri Gür; Mustafa Cengiz; Canan Vejselova Sezer; Orhan Baytar; Ömer Şahin; Adnan Ayhanci; Hatice Mehtap Kutlu
Background: The green synthesis of metallic nanoparticles has recently become a research area of increasing interest due to their potential applications in nanomedicine. Aim of study: This study aimed to investigate, for the first time, the anticancer properties of silver nanoparticles (Ag-NPs), copper oxide nanoparticles (CuO-NPs), and nickel oxide nanoparticles (NiO-NPs) on A549 and Beas-2B cell lines, as well as their antibacterial efficacy against Escherichia coli and Staphylococcus aureus strains, synthesized through a green synthesis approach utilizing Rheum ribes plant extract. Methodology: The current study introduces a sustainable and environmentally friendly method for the biosynthesis of Ag-NPs, CuO-NPs, and NiO-NPs utilizing the aqueous extract of Rhubarb (Rheum ribes). The spectroscopic and morphological properties of the Ag-NPs, CuO-NPs, and NiO-NPs obtained from the Rheum ribes extract were confirmed using different analytical techniques. Results: The Ag-NPs, CuO-NPs, and NiO-NPs exhibited different morphology with a size of about 7.90, 12.0, and 12.63 nm, respectively, and were free of impurities and highly stable particles. In addition, the NPs were further investigated for their anticancer and antibacterial properties. The anticancer effects of the NPs were assessed using the MTT assay and confocal microscopy in non-small cell lung cancer (A549) and healthy lung (Beas-2B) cells. The study results demonstrated that Ag-NPs, CuO-NPs, and NiO-NPs had cytotoxic effects on A549 cells that were concentration-based, having IC50 values of 4.16, 21.28, and 37.68 μg/mL, in that order. Additionally, it was observed that the above-mentioned NPs exhibited strong activity against bacteria. Conclusions: The nanoparticles derived from Rheum ribes extract appear to hold great potential as a class of nano-biomaterials intended for usage in biological fields.
Techno-economic and hybrid energy system analyses of hazelnut shell gasification based on geographical information system
(Elsevier Ltd, 2025) Kirim, Yavuz; Yıldız, Ertuğrul; Sadikoglu, Hasan; Melikoglu, Mehmet
In this study, electricity generation from hazelnut shells via gasification is studied in detail using Aspen Plus and economic analysis of the hazelnut gasification is thoroughly investigated. Novel to this study, hybrid energy generation potential of hazelnut shell gasification with different alternatives including PV are explored and H2 production from hazelnut shell is simulated in Aspen Plus. Mass flow of main outlet products (CO and H2) is 1103.43 kg/hr and 81.62 kg/hr, respectively. GIS is used to define the optimum area for the proposed hazelnut shell gasification plant. The production of syngas obtained from Aspen Plus simulation is estimated as 21,286,234 Nm3/yr, NPC and IRR values of the proposed gasification plant using method of time value of money are calculated as $106,673 and 28 %, respectively. NPC and COE of hybrid renewable energy system including battery storage are calculated as $6.87 M and $0.715, respectively. © 2024 Elsevier Ltd
Synthesis and properties of Schiff base Fe(II) complex
(2019) Kılınç, Dilek; Şahin, Ömer; Horoz, Sabit
In our current study, Fe (II) complex with 4-4ʹ-methylene bis (2,6-diethyl) aniline-3,5-di-tert-butylsalisilaldimine (HL1) ligand was synthesized by chemical method and the synthesized Fe (II) complex with HL1 ligand was named as Fe(L1)2 complex. Structural, morphological, electronic absorption and photovoltaic properties of Fe(L1)2 complex were characterized by x-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscope, electronic absorption, and current density (J)–voltage (V) measurements, respectively. The obtained result from the J-V measurement shows that Fe(L1)2 complex synthesized by the chemical method can be used as a promising sensitizer for a dye-sensitized solar cell.
Equilibrium, kinetic and thermodynamic studies for dynamic adsorption of benzene in gas phase onto activated carbon produced from elaeagnus angustifolia seeds
(Elsevier, 2019) Kutluay, Sinan; Baytar, Orhan; Şahin, Ömer
Adsorption of pollutants onto activated carbon is very important in air purification systems. In this study, the dynamic adsorption of benzene in gas phase onto activated carbon which was produced from the elaeagnus angustifolia seeds, was investigated using a laboratory-scale continuous flow fixed-bed reactor system, under atmospheric pressure. The effects of the adsorption conditions such as activated carbon particle size (180–500 μm), nitrogen (N2) gas flow rate (0.050–0.120 L min−1) as the benzene in gas phase carrier, amount of activated carbon (0.10–0.75 g), concentration of benzene in gas phase at the inlet (9.95–14.85 ppm) and the adsorption temperature (293–323 K) on both the adsorption capacity and the adsorption efficiency were examined. Adsorption efficiency was achieved up to 100% under various adsorption conditions. Adsorption kinetics data were analyzed by using the Pseudo-First Order and Pseudo-Second Order kinetic models. Langmuir, Freundlich and Dubinin-Radushkevich models were used for the analysis of adsorption isotherms. The results showed that the Langmuir isotherm and Pseudo-Second Order models described the experimental data better when compared to other models. The maximum monolayer adsorption capacity (qmax) of activated carbon was determined to be 99.8 mg g−1 for 303 K. Thermodynamic analyzes indicated that the adsorption process of benzene in gas phase onto activated carbon was spontaneous (ΔG°<0), exothermic (ΔH°<0) and physical (ΔH°<20 kJ mol−1).
Fabrication of Pure Sb2S3 and Fe (2.5%): Sb2S3 thin films and ınvestigation their properties
(2019) Nar, Seren; Şahin, Ömer; Horoz, Sabit
Pure Sb2S3 and Fe (2.5%): Sb2S3 thin films were synthesized on Zn2SnO4 coated with FTO conductive glasses using chemical bath deposition (CBD) technique. The X-ray diffraction (XRD) patterns obtained show that both thin films have an orthorhombic structure. Although the crystal structure of the two thin films was the same, the crystalline size of Fe (2.5%): Sb2S3 thin film (51.15 nm) was found to be smaller than that of pure Sb2S3 (52.89 nm). The effect of Fe doped metal on crystal size of Sb2S3 was observed with this result. Another important observation is that the energy band gap of Fe (2.5%): Sb2S3 thin film (2.00 eV) is larger than that of pure Sb2S3 (1.89 eV). The photovoltaic properties of the synthesized thin films were examined by applying both incident photon-to-current efficiency (IPCE) and current density (J)–voltage (V) measurements. The obtained IPCE(%) values at 600 nm for pure Sb2S3 and Fe (2.5%): Sb2S3 thin films are 30.29 and 49.06, respectively. Using the J–V curves, the calculated η (%) values for pure Sb2S3 and Fe (2.5%): Sb2S3 thin films are 3.95 and 5.44, respectively. Based on the data obtained from both measurements, it was observed that the Fe dopant significantly enhance the performance of the Sb2S3-based solar cell devices.
Catalytic activity of cobalt-boron-fluoride particles with different solvent mediums on sodium borohydride hydrolysis for hydrogen generation
(Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2019) İzgi, Mehmet Sait; Şahin, Ömer; Baytar, Orhan; Saka, Cafer
Catalysts prepared in a different solvent medium have different activities because of its different acidity, basicity and viscosity properties. The synthesis mechanism of cobalt-boron-fluoride in water, propanol and ethanol solvents was evaluated. Characterization studies of cobalt-boron-fluoride catalyst were performed with Brunauer-Emmett-Teller surface area, X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy- energy dispersive x-ray spectroscopy measurements. The effects of sodium borohydride (SB), and temperature on the SB hydrolysis reaction with the catalyst samples were studied. The maximum hydrogen generation rate (HGRs) of the cobalt-boron (ethanol solvent) and cobalt-boron-fluoride (ethanol solvent) catalysts were 1942 and 4533 mlmin−1g−1, respectively. The activation energy was 32.45 kJ mol−1.
Production of metal-free catalyst from defatted spent coffee ground for hydrogen generation by sodium borohyride methanolysis
(elsevier, 27.08.2019)
In the present study, defatted spent coffee ground (DSCG) treated with different acids was used as a metal-free catalyst for the first time. The aim of undertaken work is to demonstrate that DSCG can be used as a green catalyst to produce hydrogen through methanolysis of sodium borohydride. To produce hydrogen by the sodium borohydride methanolysis (NaBH4), DSCG was pretreated with different acids (HNO3, CH3COOH, HCl). According to the superior acid performance, acetic acid was selected and then different concentrations of the chosen acid were evaluated (1M, 3M, 5M, and 7M). Subsewuently, different temperatures (200, 300, 400 and 500 °C) and burning times (30, 45, 60 and 90 min) for the optimization of DSCG-catalyst were tested. The experiments with the use of CH3COOH treated DSCG-catalyst reveal that the optimal acid concentration was 1M CH3COOH and the burning temperatures and time were 300 °C and 60 min, respectively. FTIR, SEM, ICP-MS and CHNS elemental analysis were carried out for a through characterization of the catalyst samples. In this study, the experiments were carried out with 10 ml methanol solution contained 0.025 g NaBH4 with 0.1 g catalyst at 30 °C unless otherwise stated. The effect of NaBH4 concentration was investigated with use of 1%, 2.5%, 5%, and 7.5% NaBH4, while the influence of catalyst concentration was discovered with the use of 0.05, 0.1, 0.15, and 0.25 g catalyst. Different temperatures were chosen (30, 40, 50 and 60 °C) to explore the hydrogen production performance of the catalyst. In addition, the maximum hydrogen production rate through methanolysis reaction of NaBH4 by this catalyst was found to be 3171.4 mL min−1gcat−1. Also, the activation energy was determined to be 25.23 kJ mol−1.
Determination of Nucleation Kinetics of Ammonium Biborate Tetrahydrate
(2014) Demir, Halil
The ammonium biborate tetrahydrate was synthesized by stoichiometric incorporation of boric acid and ammonium hydroxide in aqueous solution and the effects of supersaturation, temperature, pH of solution, cooling rate and presence of impurities upon the metastable zone width (MZW) were investigated. The MZW of ammonium biborate tetrahydrate aqueous solution was increased with increasing concentration of impurities. The saturation temperature was increased in the presence of Ca (II) ion and decreased in the presence of Pb (II) and Mg (II) ions.
Hydrogen Generation from Sodium Borohydride Hydrolysis with a Cu–Co-Based Catalyst: A Kinetic Study
(Taylor and francis, 2015) Demir, Halil
In the present work, Cu–Co-supported catalysts were tested for hydrogen generation from the hydrolysis reaction of an alkaline sodium borohydride solution. Cu–Co catalysts were prepared by the chemical reduction with NaBH4 and characterized with scanning electron microscope. The effect of Cu–Co ratio was investigated. The results suggested that the optimal mixture percentage of Cu–Co catalyst was 60:40; excessive Cu resulted in poor catalytic activity. The reactions were carried out at temperatures of 20, 30, 40, and 50°C. The experimental data was fitted to the nth-order kinetic models. The results indicate that the nth-order model gives a reasonable description of the hydrogen generation rate over all of the temperature range. The activation energy and pre-exponential factor of the nth-order reaction model were obtained as 42.66 kJ mol−1 and 1.21 × 104, respectively.
Preparation and Characterization of Activated Carbon from Microwave and Conventional Heated Almond Shells Using Phosphoric Acid Activation
(Analytical Letters, 2019) İZGİ, Mehmet Sait; Gamze Saraçoğlu; Baytar, Orhan; Şahin, Ömer; Saka, Cafer
Activated carbon production from almond shells using phosphoric acid activation agent was achieved by applying both conventional heating and microwave heating in succession. The morphology and surface properties of activated carbon were studied using thermogravimetric and differential gravimetric analysis, Fourier-transform infrared spectroscopy, scanning electron microscopy, and Brunauer–Emmett–Teller analysis. A surface area of 1128 m2/g was achieved by optimizing the microwave power (500 W), microwave application time (15 minutes), conventional heating time (45 minutes), conventional heating temperature (500 °C), and the phosphoric acid:sample ratio (0.7:1). An adsorption capacity of methylene blue of 148 mg/g and an iodine value of 791 mg/g was obtained for the prepared activated carbon.
γ-Al2O3 supported/Co-Cr-B catalyst for hydrogen evolution via NH3BH3 hydrolysis
(Materials and Manufacturing Processes, 2019) İZGİ, Mehmet Sait; Saka, Cafer; Şahin, Ömer
This assay investigates the Co-Cr-B catalyst effect supported on γ-Al2O3 to produce hydrogen (HG) from ammonia-borane hydrolysis (ABH). For characterization of this catalyst, SEM-EDX, XRD, FTIR and BET surface area analysis were performed. The maximum hydrogen generation rate (HGR) with this catalyst used for the ABH was 3260 ml min−1 g−1catalyst. The recyclability tests for the Co-Cr-B/γ-AlO3 catalyst on the ABH have maintained an activity of 68% even after four hydrolysis treatments. Also, the activation energy (Ea) obtained using the Co-Cr-B catalyst supported on γ-AlO3 for the ABH was 56.06 kJ/mol.
Novel activated carbon supported trimetallic PdCoAg nanoparticles as efficient catalysts for the hydrolytic dehydrogenation of ammonia borane
(Journal of Hydrogen Energy, 2019) Mehmet Sait İZGİ
Activated carbon (AC) supported palladium, cobalt and silver nanoparticle (PdCoAg/AC) catalysts were prepared by in situ reduction of sodium borohydride (NaBH4) and characterized by various techniques such as X-ray diffraction (XRD), scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDX), Transmission electron microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS). The PdCoAg/AC catalyst is active in the hydrolysis of ammonia-borane (AB) even at low temperatures. Compared with mono- (Pd) and bi-metallic (PdCo) nanoparticles, this trimetallic (PdCoAg) structure showed greatly increased catalytic activity for AB hydrolysis. Their hydrolysis completion time was 50 s. This study also included full experimental details of kinetic data to determine the activation parameters (Ea, and ) for the rate law and the catalytic hydrolysis of AB. In addition, the PdCoAg/AC catalysts had favorable catalytic activity also after seven runs. Hydrogen generation rate (HG), Ea, and were obtained at 25 °C as 4666.66 mL min−1g−1 (2 mmol AB and 50 mg PdCoAg/AC), 26.836 kJ mol-1, 29.416 kJ mol−1and –108.42 J mol−1K−1, respectively. In addition, the study showed that Pd0.6Co0.2CAg0.2/AC (Pd:Co:Ag atomic ratio = 6:2:2) showed the total turnover frequency (TOF) value of 6624 h−1. These results demonstrate that the PdCoAg/AC catalyst is a promising alternative in search of the practical application of AB as a hydrogen storage material for fuel cell applications.
Hydrogen production through the cooperation of a catalyst synthesized in ethanol medium and the effect of the plasma
(Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2019-10) Mehmet Sait, İZGİ; Ömer, Şahin; Erhan, Onat; Hilal, Çelik Kazıcı
In the present study, nanostructured Ni-B catalysts were successfully prepared in ethanol medium using the chemical reduction method for hydrogen production from the catalytic hydrolysis of sodium borohydride (NaBH4). Ni-B nanostructures were characterized by several analysis methods including XRD, SEM/EDS, FT-IR and BET. The effects of factors such as solution temperature, NaBH4 loadings, catalyst amount and NaOH concentration on the performance of these catalysts in the production of hydrogen from alkaline NaBH4 solutions were investigated in detail. In addition, the Ni-B catalyst prepared in ethanol medium and subjected to plasma for the hydrogen production from the catalytic hydrolysis of NaBH4 was investigated. The Ni-B catalyst prepared in ethanol medium showed maximum hydrogen production rate (1000 mL min-1gcatalyst-1) which was approximately 2 times higher than the rate obtained from the Ni-B catalyst prepared in water (400 mL min-1gcatalyst-1) and acethone (550 mL min-1gcatalyst-1). The Ni-B nanoparticles showed the best catalytic activity at 333 K with a maximum hydrogen production rate of 7134 mL min-1gcatalyst-1 and activation energy of 46.83 kJmol-1 for the NaBH4 hydrolysis reaction in the Ni-B catalysts prepared in ethanol and subjected to plasma. As the Ni-B catalyst is inexpensive and easy to prepare, it is feasible to use this catalyst in the construction of practical fuel cells for portable and in situ applications.
Comparison of newly developed hydroxyl- functionalized monodisperse HILIC columns new HILIC column
(Journal of Liquid Chromatography & Related Technologies, 2017) Dinç, Saliha; Samatya Ölmez, Saba; Tuncel, Ali
In this study, new hydroxyl-functionalized monodisperse polymeric hydrophilic interaction chromatography (HILIC) columns were developed using different derivatization agents. In addition, the influences of derivatization temperature of the best agent and polymer composition on the separation were investigated under HILIC conditions. Monodisperse–porous hydrophilic particles were synthesized by the seeded polymerization method using 3-chloro-2-hydroxypropile methacrylate (HPMA-CL) and ethylene glycol dimethacrylate (EGDMA) monomers. The chloropropyl terminal ends of the poly(HPMA-Cl-coEGDMA) particles were derivatized with amine group of ethanolamine (EA), diethanolamine, and triethanolamine (TEA) at 80°C through nucleophilic reaction. The performance of synthesized particles was evaluated with the amount of ligand on the particle surfaces, column backpressure, and separation power under HILIC condition. TEA was found to be the best derivatization agent for the separation of toluene, acrylamide, thymine, adenine, and cytosine in respect to resolution factors (>1.5 for all analytes) and theoretical plate numbers (64.562 N/m for acylamide). Upon determination of the best ligand, then the effect of different derivatization temperatures and polymer composition on TEA performance was investigated. Of all the tested polymer compositions, the chromatographic performance of TEA-M-80 (the derivatization of TEA at 80°C together with M polymer composition) was found to be the best.
Hydrogen generation from hydrolysis of sodium borohydride with Ni (0) catalyst in dielectric barrier discharge method
(Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2014-09-02) Şahin, Ömer; Baytar, Orhan; Hansu, Fevzi; Saka, cafer
In this study, the hydrogen production from hydrolysis of sodium borohydride (NaBH4) in the presence of the catalytic properties of Ni(0), which is reduced from NiCl2.6H2O, was investigated with a dielectric barrier discharge plasma method. The hydrogen production from NaBH4 hydrolysis with Ni(0) catalyst prepared in dielectric barrier discharge plasma media created by applying a certain amount of voltages (3–5 kV) and plasma applying times (5–15 min) was investigated depending on NaBH4 concentration (3.2–10%) in solutions, NaOH concentration (1.5–10%) in solutions, catalyst amount (5–20 mg), and temperature (20–60°C). Hydrolysis reaction of NaBH4 with Ni(0) prepared in the presence of dielectric barrier discharge plasma is completed in 45-min time intervals with fast hydrogen generation while the Ni(0) produced in a known method led to a slow hydrogen release and hydrolysis is completed in 70-min time intervals. The hydrogen yield of 3.2, 5, and 10% NaBH4 solution with Ni(0) catalyst prepared in the presence of dielectric barrier discharge plasma takes the values of 95.06, 57.42, and 31.78% at the end of 45 min, respectively. The experimental data were fitted to first-order. The activation energy for first-order was found to be 41.76 kJ mol-1.
Influence of plasma treatment on electrochemical activity of Ni (o)-based catalyst for hydrogen production by hydrolysis of NaBH 4
(Journal of Power Sources, 2013-10-15) Şahin, Ömer; Saka, cafer; baytar, Orhan; Hansu, Fevzi
n this study, the hydrogen generation from the hydrolysis of NaBH4 with Ni (o) catalyst prepared in the presence of plasma is investigated. The catalytic properties of nickel catalyst prepared in the presence of plasma are investigated based on NaBH4 concentration, NaOH concentration, temperature, plasma applying time and plasma applying voltage. The results indicated that nickel catalyst reduced with plasma was completed in only 35 min, while the nickel catalyst produced in known method is completed in 80 min. Characteristics of this nickel-based catalyst are carried out by using XRD, BET, SEM and XPS. The activation energy for zero-order is found to be 51.35 kJ mol-1.

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