Researcher:
Öztulum, Samira Fatma Kurtoğlu

Profile Picture
ORCID

Job Title

PhD Student

First Name

Samira Fatma Kurtoğlu

Last Name

Öztulum

Name

Name Variants

Öztulum, Samira Fatma Kurtoğlu

Email Address

Birth Date

Filters

2016 - 201942020 - 202214

Advanced Search

Filter by

Settings

Researcher Of Publications: search.filters.isAuthorOfPublication.7f4b6ff5-8d76-4665-8d44-1fa437659a52

Search Results

Now showing 1 - 10 of 18
  • Placeholder
    PublicationMetadata only
    Graphene aerogel-supported ruthenium nanoparticles for COx-free hydrogen production from ammonia
    (Elsevier, 2021) N/A; N/A; N/A; Department of Chemical and Biological Engineering; Department of Chemistry; Department of Chemistry; Koçer, Tolga; Öztulum, Samira Fatma Kurtoğlu; Uzun, Alper; Ünal, Uğur; Öztuna, Feriha Eylül Saraç; Researcher; PhD Student; Faculty Member; Faculty Member; Researcher; Department of Chemical and Biological Engineering; Department of Chemistry; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); N/A; Graduate School of Sciences and Engineering; College of Engineering; College of Sciences; College of Sciences; N/A; 384798; 59917; 42079; N/A
    Ruthenium was highly dispersed on graphene aerogel (GA) at high loadings to achieve high performance in COx-free hydrogen production from ammonia. Catalytic performance measurements on ammonia decomposition showed that the GA-supported catalyst with a Ru loading of 13.6 wt% provides an ammonia conversion of 71.5 % at a space-velocity of 30,000 ml NH3 g(cat)(-1)h(-1) and at 450 degrees C, corresponding to a hydrogen production rate of 21.9 mmol H-2 g(cat)(-1)min(-1). The addition of K increased the ammonia conversion to a record high value of 97.6 % under identical conditions, reaching a hydrogen generation rate of 30.0 mmol H-2 g(cat)(-1) min(-1), demonstrated to be stable for at least 80 h. A comparison of the turnover frequencies of catalysts indicated that this increase in performance upon the addition of K originated from an increase in the number of the active Ru sites and the corresponding electron density available for reaction.
  • Placeholder
    PublicationMetadata only
    Transformation of reduced graphene aerogel-supported atomically dispersed iridium into stable clusters approximated as Ir-6 during ethylene hydrogenation catalysis
    (Elsevier, 2022) Zhao, Yuxin; Hoffman, Adam S.; Gates, Bruce C.; Bare, Simon R.; Department of Chemistry; Department of Chemical and Biological Engineering; N/A; N/A; N/A; Ünal, Uğur; Uzun, Alper; Öztulum, Samira Fatma Kurtoğlu; Yalçın, Kaan; Çağlayan, Hatice Pelin; Faculty Member; Faculty Member; PhD Student; Master Student; Master Student; Department of Chemistry; Department of Chemical and Biological Engineering;  Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); College of Sciences; College of Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; 42079; 59917; 384798; N/A; N/A
    Transformation of atomically dispersed reduced graphene aerogel (rGA)-supported complexes, Ir-I(C2H4)(2)(+), with an iridium loading of 9.9 wt%, to form low-nuclearity clusters was investigated during ethylene hydrogenation catalysis. Continuous-scan X-ray absorption spectra demonstrate the formation of clusters well approximated as Ir-4 during reaction at 100 degrees C in flowing equimolar ethylene and H-2. The Ir-4 clusters transformed into clusters well approximated as Ir 6 when the feed molar ratio was switched to H-2: C2H4 = 2 and remained stable in pure H-2 at 100 degrees C. Catalyst performance data show that hydrogenation activity increased with metal nuclearity in the order of atomically dispersed iridium/rGA << Ir-4/rGA < Ir-6/ rGA. Continuous scan X-ray absorption data, complemented with aberration-corrected scanning transmission electron microscopy images, demonstrate that the supported clusters approximated as Ir-6 are stable even in H-2 at atmospheric pressure and 100 degrees C. These supported iridium clusters are among the ones having the highest metal loadings reported for a supported metal cluster catalyst.
  • Placeholder
    PublicationMetadata only
    Ionic liquid sheath stabilizes atomically dispersed reduced graphene aerogel-supported iridium complexes during ethylene hydrogenation catalysis
    (Wiley, 2022) Hoffman, Adam S.; Gates, Bruce C.; Bare, Simon R.; N/A; N/A; N/A; N/A; Department of Chemical and Biological Engineering; Department of Chemistry; Öztulum, Samira Fatma Kurtoğlu; Yalçın, Kaan; Jalal, Ahsan; Zhao, Yuxin; Uzun, Alper; Ünal, Uğur; PhD Student; Master Student; PhD Student; PhD Student; Faculty Member; Faculty Member; Department of Chemical and Biological Engineering; Department of Chemistry; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Sciences; 384798; N/A; N/A; N/A; 59917; 42079
    An atomically dispersed reduced graphene aerogel (rGA)-supported iridium catalyst having reactive ethylene ligands was synthesized at an iridium loading of 9.9 wt % and coated with an ionic liquid, 1-ethyl-3-methylimidazolium acetate ([EMIM][OAc]). Continuous-scan X-ray absorption spectra demonstrated that the iridium remained site-isolated in flowing equimolar C2H4 and H-2 during a temperature ramp to 100 degrees C. The data further showed the lack of detectable iridium aggregation when the feed was H-2-rich or even pure H-2 at 100 degrees C. An Arrhenius plot determined for ethylene hydrogenation catalysis with the sample in flowing equimolar ethylene and hydrogen showed no variation in the apparent activation energy at temperatures up to 100 degrees C, confirming that the active sites remained intact at the higher temperatures. The results point to opportunities for overcoming the stability limitations of atomically dispersed supported noble metal catalysts by choice of electron-donor supports and ionic liquid sheaths.
  • Placeholder
    PublicationMetadata only
    Tuning structural characteristics of red mud by simple treatments
    (Elsevier Sci Ltd, 2016) Soyer-Uzun, Sezen; N/A; Department of Chemical and Biological Engineering; Öztulum, Samira Fatma Kurtoğlu; Uzun, Alper; PhD Student; Faculty Member; Department of Chemical and Biological Engineering; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Graduate School of Sciences and Engineering; College of Engineering; 384798; 59917
    Red mud (RM) is a hazardous waste produced vastly by aluminum industry worldwide. Because of its rich metal oxide content, it has potential to be utilized in various applications, such as ceramics production, construction, and catalysis. Here, we investigated the structural modification of RM by simple acid treatments using HCl and H2SO4 at different molarities, and at different digestion temperatures followed by calcinations at various temperatures. Structures before and after these treatments were characterized in deep detail by combining electron microscopy, diffraction, and spectroscopy complemented by thermal analysis and mass spectrometry to elucidate any changes in morphology, structure, and chemical composition introduced by these treatments. Results showed that acid treatments tremendously affect chemical composition; for instance, amount of Fe2O3 changes from 37 to 46 wt%, while that of minor components, such as Na2O, varies from approximately 9 wt% to trace amounts. Moreover, data also illustrated that high acid digestion temperature (220 degrees C) leads to significant improvements in surface area, from 17 m(2)/g to values exceeding 200 m(2)/g. Results presented here provide a guideline for modifying RM by simple treatments to tune its structural characteristics, potentially offering opportunities for its utilization as cost effective and environmentally friendly solutions to various applications.
  • Placeholder
    PublicationMetadata only
    Consequences of simple acid-pretreatments on geopolymerization and thermal stability of red mud-based geopolymers
    (Amer Chemical Soc, 2018) Kaya, Kardelen; Soyer Uzun, Sezen; N/A; Department of Chemical and Biological Engineering; Öztulum, Samira Fatma Kurtoğlu; Uzun, Alper; Researcher; Faculty Member; Department of Chemical and Biological Engineering; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Graduate School of Sciences and Engineering; College of Engineering; N/A; 59917
    Red mud, a solid waste residue that forms as a by-product of the Bayer process in alumina production, is structurally modified by simple acid treatments (using 2 and 6 M HCl with digestion temperatures of 85 and 220 degrees C, respectively) followed by calcination at 800 degrees C prior to employing it as a raw material in geopolymer synthesis. The raw materials and their geopolymers are characterized by combining X-ray diffraction, Fourier transform infrared spectroscopy, X-ray fluorescence spectroscopy, thermogravimetric analysis, pore volume and surface area analysis, and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. Results reveal that acid modification of red mud followed by calcination plays an important role in activating red mud, significantly leading to enhanced geopolymerization and increased thermal stability of the corresponding geopolymers. The findings presented here can offer new opportunities for effective large-scale utilization of other waste material-based systems in geopolymerization.
  • Placeholder
    PublicationMetadata only
    Thermal stability limits of imidazolium, piperidinium, pyridinium, and pyrrolidinium ionic liquids immobilized on metal oxides
    (Elsevier, 2022) N/A; N/A; N/A; Department of Chemical and Biological Engineering; Öztulum, Samira Fatma Kurtoğlu; Jalal, Ahsan; Uzun, Alper; PhD Student; PhD Student; Faculty Member; Department of Chemical and Biological Engineering; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; 384798; N/A; 59917
    Twenty-nine different ionic liquids (ILs) consisting of imidazolium, pyridinium, piperidinium, and pyrro-lidinium cations and I-, Cl-, Br-, PF6-, BF4-, [DCA]-, and [NTf2]- anions were immobilized on MgO and SiO2. Their short-term thermal stability limits were investigated by thermogravimetric analysis and compared with those of the corresponding bulk ILs. Data showed that the thermal stability limits of ILs change sig-nificantly when the ILs are immobilized on metal oxides. These changes were evaluated based on the structural interactions determined by infrared (IR) spectroscopy. Systematic structural differences were considered to investigate the factors affecting the thermal stability of bulk ILs, and their counterparts immobilized on MgO and SiO2. These structural changes were the change in the alkyl chain length, the methylation on C2 site in imidazolium ILs, the change in substituent position in the pyridinium ring, the change in the anion, and the change in the IL family. The strongest factor controlling the thermal sta-bility limits of both bulk ILs and their supported counterparts was determined as the anion type. Accordingly, the basicity of the anion and the surface acidity of the metal oxide and their resulting inter-actions were found to have a significant effect on the thermal stability limits. Data presented here offer the opportunity to pick a suitable anion and cation pair according to the metal oxide, so that the sup-ported IL can withstand the desired operation conditions in various applications, such as catalysis or gas separation.
  • Placeholder
    PublicationMetadata only
    Effect of nickel precursor on the catalytic performance of graphene aerogel-supported nickel nanoparticles for the production of cox-free hydrogen by ammonia decomposition
    (Wiley-V C H Verlag Gmbh, 2022) N/A; N/A; N/A; Department of Chemical and Biological Engineering; Department of Chemistry; Department of Chemistry; Koçer, Tolga; Öztulum, Samira Fatma Kurtoğlu; Uzun, Alper; Ünal, Uğur; Öztuna, Feriha Eylül Saraç; Researcher; PhD Student; Faculty Member; Faculty Member; Researcher; Department of Chemical and Biological Engineering; Department of Chemistry; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); N/A; Graduate School of Sciences and Engineering; College of Engineering; College of Sciences; College of Sciences; N/A; 384798; 59917; 42079; N/A
    Graphene aerogel (GA), a promising porous material with high specific surface area and electrical conductivity, is utilized to disperse nickel nanoparticles to reach high catalytic activity in COx-free hydrogen production from ammonia. Ni(NO3)(2)center dot 6H(2)O and Ni (II) acetylacetonate (Ni(acac)(2)) were considered as metal precursors and the pH of the impregnation solution was varied to investigate the effects on the catalytic properties of the GA-supported nickel catalysts. Data showed that the best dispersion and homogeneity, as well as the catalytic performance, is achieved with Ni(acac)(2). An average Ni nanoparticle size of 13.6 +/- 4.3 nm was obtained on the GA-supported catalyst prepared by using Ni(acac)(2) dissolved in an impregnation solution with a pH of 10.2. This catalyst with a Ni loading of 11.1 wt% provided an ammonia conversion of 70.2% at a space velocity of 30 000 mL NH3 g(cat)(-1) h(-1) and 600 degrees C corresponding to a hydrogen production rate of 21.5 mmol H-2 g(cat)(-1) min(-1). Data illustrated that the difference between the point of zero charge of the support and the pH of the impregnation solution set by the type of the Ni precursor is a major parameter controlling the metal dispersion and the consequent catalytic activity.
  • Placeholder
    PublicationMetadata only
    Utilizing red mud modified by simple treatments as a support to disperse ruthenium provides a high and stable performance for COx-free hydrogen production from ammonia
    (Elsevier, 2020) Soyer-Uzun, Sezen; N/A; Department of Chemical and Biological Engineering; Öztulum, Samira Fatma Kurtoğlu; Uzun, Alper; PhD Student; Faculty Member; Department of Chemical and Biological Engineering; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; College of Engineering; 384798; 59917
    Red mud (RM), the by-product of aluminum industry produced in vast amounts, is a hazardous waste rich in Fe2O3, an active component for various reactions. Here, we used RM modified by simple acid treatments as a support for dispersing Ru to obtain a highly efficient catalyst for ammonia decomposition. Catalytic performance measurements showed that the catalyst prepared by 5 wt.% Ru loading on modified red mud (MRM) provides 99.6% conversion at a significantly high space velocity of 240 000 cm(3) NH3 h(-1) g(cat)(-1) at 700 degrees C. XRD spectrum of the used catalyst illustrates high dispersion of Ru confirmed by the absence of Ru diffraction peaks and the formation of Fe3Ny moieties contributing to the catalytic activity. Time-on-stream measurements show that the catalyst is superior in terms of stability as it provides a stable performance for up to seven days. Data illustrated that MRM both acts as an iron nitride-based catalyst itself and as a robust support for Ru crystallites which synergistically results in a high and stable performance. Findings presented here enable the remediation of an industrial waste by utilizing RM as an almost cost-free, robust, and efficient support for Ru.
  • Placeholder
    PublicationMetadata only
    Enhancing biocompatibility of NiTi shape memory alloys by simple NH3 treatments
    (Elsevier, 2020) N/A; N/A; N/A; Department of Chemical and Biological Engineering; Department of Chemistry; Department of Mechanical Engineering; Öztulum, Samira Fatma Kurtoğlu; Yağcı, Mustafa Barış; Uzun, Alper; Ünal, Uğur; Canadinç, Demircan; PhD Student; Researcher; Faculty Member; Faculty Member; Faculty Member; Department of Chemical and Biological Engineering; Department of Chemistry; Department of Mechanical Engineering; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; N/A; College of Engineering; College of Sciences; College of Engineering; 384798; N/A; 59917; 42079; 23433
    This paper presents the treatment of NiTi shape memory alloys (SMAs) in flowing ammonia at 700 degrees C as a simple and cost-effective nitriding process to provide a protective surface layer hindering Ni ion release in biological environments. Experimental results demonstrated that a smooth protective TiN layer on the NiTi SMAs along with TiOxNy and TiO2 formed on the surface upon treating the as-received NiTi SMA in ammonia at 700 degrees C. The protective TiN layer and the smooth surface hinder the amount of Ni ion release to artificial saliva (AS) after 28 days of immersion, while the dry air treatment at similar conditions results in a significantly rough surface, leading to about 20 times higher Ni ion release. Overall, the findings presented herein demonstrate that NH3 nitriding is an effective method to eliminate the Ni presence from the surface and to obtain a smooth final surface, which, in turn, restricts the Ni ion release from the NiTi SMA into AS. Consequently, nitriding the surface of NiTi under NH3 at 700 degrees C turned out as a promising method to lower Ni ion release and thereby contribute to the biocompatibility of NiTi SMAs, which, however; needs to be further validated through further experimentation.
  • Placeholder
    PublicationMetadata only
    COx-free hydrogen production from ammonia decomposition over sepiolite-supported nickel catalysts
    (Pergamon-Elsevier Science Ltd, 2018) Soyer-Uzun, Sezen; N/A; N/A; N/A; N/A; Department of Chemical and Biological Engineering; Öztulum, Samira Fatma Kurtoğlu; Sarp, Seda; Akkaya, Ceren Yılmaz; Yağcı, Mustafa Barış; Uzun, Alper; PhD Student; Undergraduate Student; Researcher; Researcher; Faculty Member; Department of Chemical and Biological Engineering; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; N/A; College of Engineering; 384798; N/A; N/A; N/A; 59917
    Sepiolite, a clay mineral, was utilized as a support for nickel-based catalysts for COx-free hydrogen production from ammonia decomposition. First, the physical and chemical properties of sepiolite were changed by calcining it at temperatures varying from 500 to 1000 degrees C, then nickel was impregnated on these calcined supports and tested for ammonia decomposition at various temperatures following reduction at 650 degrees C. Results indicated that even though the catalysts contained almost the same amount of nickel, they showed different hydrogen production performance. Detailed characterization of the catalysts before and after reaction illustrated that the support obtained by calcining sepiolite at 700 degrees C shows good basic properties with a high surface area offering a high degree of nickel dispersion. These properties lead to promising hydrogen production rates which are on par, if not higher, than most of the nickel-based catalysts prepared on supports, which are either not cheap or require tedious preparation procedures.