1,721,026 research outputs found
Supported Copper-Copper Oxide Nanoparticles as Active, Stable and Low-Cost Catalyst in the Methanolysis of Ammonia-Borane for Chemical Hydrogen Storage (vol 165, Pg 169, 2015)
No full textErtas, Ilknur Efecan/0000-0003-0997-7523; Yurderi, Mehmet/0000-0002-0233-8940; Yurderi, Mehmet/0000-0002-6761-3763; Kaya, Murat/0000-0002-2458-8924; Bulut, ahmet/0000-0002-1697-8623[No Abstract Available
Supported Copper-Copper Oxide Nanoparticles as Active, Stable and Low-Cost Catalyst in the Methanolysis of Ammonia-Borane for Chemical Hydrogen Storage
No full textYurderi, Mehmet/0000-0002-0233-8940; Bulut, ahmet/0000-0002-1697-8623; Ertas, Ilknur Efecan/0000-0003-0997-7523; Yurderi, Mehmet/0000-0002-6761-3763; Kaya, Murat/0000-0002-2458-8924The physical mixture of copper (Cu) copper(I) oxide (Cu2O) and copper(II) oxide (CuO) nanoparticles supported on activated carbon (Cu-Cu2O-CuO/C) were reproducibly prepared by a simple deposition-reduction technique without using any stabilizer in water at room temperature. The characterization of the resulting material by ICP-OES, P-XRD, XPS, DR-UV/vis, BFTEM and HRTEM techniques reveals that the formation of well-dispersed highly crystalline 3.8 +/- 1.7 nm nanoparticles on the surface of activated carbon. These carbon supported Cu-Cu2O-CuO nanoparticles were employed as heterogeneous catalyst in the methanolysis of ammonia-borane (NH3BH3), which has been considered as one of the attractive materials for the efficient storage of hydrogen, under mild conditions. We found that only 3.0 mol % Cu-Cu2O-CuO/C catalyst is enough to catalyze the methanolysis of ammonia-borane with high activity (TOF = 24 min(-1)) and conversion (>99%) at room temperature. More importantly, the exceptional stability of supported Cu-Cu2O-CuO nanoparticles against to sintering and leaching make Cu-Cu2O-CuO/C recyclable catalyst for the methanolysis of ammonia-borane. Cu-Cu2O-CuO/C catalyst retains >76% of its initial activity with 94% of conversion even at 8th recycle in the methanolysis of ammonia-borane at complete conversion. The study reported here also includes the collection of kinetic data for Cu-Cu2O-CuO/C catalyzed methanolysis of ammonia-borane depending on catalyst [Cu], substrate [NH3BH3] concentrations and temperature to determine the rate expression and the activation parameters (E-a, Delta H-#, and Delta S-#) of the catalytic reaction. (C) 2014 Published by Elsevier B.V.Fevzi Akkaya Scientific Activities Support Fund (FABED); Science Academy and Turkish Academy of Sciences (TUBA)The partial supports by Fevzi Akkaya Scientific Activities Support Fund (FABED), Science Academy and Turkish Academy of Sciences (TUBA) are gratefully acknowledged
Pdau-mno<i><sub>x</Sub>< Nanoparticles Supported on Amine-Functionalized Sio<sub>2</Sub> for the Room Temperature Dehydrogenation of Formic Acid in the Absence of Additives
No full textDemir KIVRAK, Hilal/0000-0001-8001-7854; Karatas, Yasar/0000-0002-9171-7781; Yurderi, Mehmet/0000-0002-0233-8940; Bulut, ahmet/0000-0002-1697-8623; Ertas, Ilknur Efecan/0000-0003-0997-7523; Çelebi, Metin/0000-0003-1475-8878; Kivrak, Hilal/0000-0001-8001-7854; Yurderi, Mehmet/0000-0002-6761-3763; Gulcan, Mehmet/0000-0002-3921-8811; Kaya, Murat/0000-0002-2458-8924Formic acid (HCOOH) has recently been suggested as a promising hydrogen carrier for fuel cell applications. However efficient hydrogen production through the decomposition of formic acid in the absence of additives under mild thermodynamic conditions constitutes a major challenge because of the ease poisoning of active metals with CO formed as intermediate during formic acid decomposition. Recently, we have reported (App. Catal. B: Env. 164 (2015) 324) our discovery that the separately nucleated MnOx nanoparticles act as CO-sponge around catalytically active Pd nanoparticles exist on the same support and enhances both the activity and CO-resistivity of Pd nanoparticles. Using this important finding, herein, we present a new catalyst system consists of the physical mixture of PdAu alloy and MnOx nanoparticles supported on amine-grafted silica (PdAu-MnOx/N-SiO2) for the room temperature dehydrogenation of formic acid in the absence of any additives. PdAu-MnOx/N-SiO2 catalyst was simply prepared by deposition-reduction technique in water at room temperature with high reproducibility and characterized by the combination of various spectroscopic tools including ICP-OES, P-XRD, DR/UV-vis, XPS, BFTEM, STEM-EDX, STEM-line analysis and CO-stripping voltammetry techniques. The sum of their results shows that the formation of physical mixture of PdAu alloy and MnOx (dmean=2.2 nm) nanoparticles on the surface of support material. This new catalytic material facilitates the hydrogen liberation through the additive-free formic acid dehydrogenation at room temperature with previously unprecedented activity (TOF=785 mol H-2 mol catalyst(-1) h(-1)), converging to that of the existing state of the art homogenous catalysts. This new superior catalytic system enables facile catalyst recovery and very high stability against agglomeration, leaching and CO poisoning, which make it highly reusable catalyst (retains >92% activity and 85% conversion at the 5th catalytic reuse) in the additive-free formic acid dehydrogenation at room temperature. (C) 2015 Elsevier B.V. All rights reserved.Yuzuncu Yil University Office of Scientific Research Projects; Science Academy; Turkish Academy of Sciences (TUBA)MZ thanks to Yuzuncu Yil University Office of Scientific Research Projects for the financial support to his research laboratory. Additionally, the partial supports by Fevzi Akkaya Scientific Activities Support Fund (FABED), Science Academy and Turkish Academy of Sciences (TUBA) are gratefully acknowledged
The investigation of the catalytic performance of rhodium nanoparticles supported on uio-66 metal-organic framework in the hydrolysis of dmnp
No full textSoman (GD) gibi organofosfor (OP) bazlı kimyasal savaş ajanları (KSA), vücutta bulunan sinir sisteminden kaslara birçok sistemde sinyal iletimini bozabilen ve 0.01 ppm kadar düşük konsantrasyonlara maruz kaldığında dahi ölümle sonuçlanan en zararlı KSA sınıflarından biridir. Bu nedenle, bu gazların yapısındaki öldürücü OP bileşiğinin yakalanması ve/veya bozunması için kişisel koruyucu kıyafet veya ekipmanlarda kullanılacak ileri teknoloji malzemelerin geliştirilmesine büyük ilgi oluşmuştur. Bu zararlı KSA’leri kolayca adsorbe edebilen ve etkili bir şekilde parçalayabilen malzemelere baktığımızda ilk çalışmaların zirkonyum oksitler, hidroksitler veya titanyum oksitler gibi geçiş metallerinin oksitlerinin kullanılmasıyla gerçekleştirildiği görülmektedir. Fakat bu malzemelerin önemli bir dezavantajı düşük yüzey alanı, düşük gözeneklilik göstermesi ve de KSA’nin adsorbe edilmesinden sonra etkin bölgelerin zehirlenmesi ki bu durum da katalizörün düşük etkinlik göstermesine neden olmaktadır. Bu nedenle, sağladıkları yüksek yüzey alanı ve gözeneklere sahip kristalli organik gözenekli malzeme sınıfı olarak zirkonyum-bazlı metal-organik kafes yapılarının (Zr-MOF'lar) kullanılması çalışmaya özgünlük katmaktadır. KSA'ların veya benzerlerinin (simülantların) bozunması için MOF katalizörlerinin geliştirilmesi, en azından laboratuvar ölçekli araştırmalar için oldukça önemlidir. İşte bu bağlamda; bu çalışmada, Soman (GD) kimyasal savaş gazının simülantı olan dimetil 4-nitrofenil fosfatın (DMNP) bozunmasına yönelik katalitik hidroliz etkinliği araştırılmıştır. KSA (GD (Soman)) simulantı olan dimetil 4-nitrofenil fosfatın (DMNP) bozunmasına yönelik katalitik hidroliz etkinlik kinetiğinin UV-vis spektroskopisi (?mak. = 407 nm) yoluyla p-nitrofenoksit oluşumunun izlenmesiyle takip edilmiştir. Çalışma sonucunda DMNP’nin Rh/UiO-66 katalizörü sayesinde artan sıcaklık değerlerinde daha etkin bir tepkime ile bozunduğu görülmüştür. Ayrıca Rh/UiO-66 katalizörünün miktarı artırıldığında yine DMNP’yi daha yüksek oranlarda bozarak toksik etkisini yok ettiği görülmüştür. Son olarak olumlu sonuçlar elde edilmesinden dolayı, kullanılan Rh/UiO-66 MOF malzesinin kişisel koruyucu kıyafet veya ekipmanlara (maske, giysi vb.) entegresine yönelik bir olanak sunacağı düşünülmektedir.Organophosphorus (OP)-based chemical warfare agents (CSA), such as Soman (GD), are one of the most harmful classes of CSA, which can disrupt signal transmission in many systems in the body, from the nervous system to the muscles, resulting in death even when exposed to concentrations as low as 0.01 ppm. For this reason, there has been great interest in the development of advanced technology materials to be used in personal protective clothing or equipment to capture and/or degrade the lethal OP compound in the structure of these gases. When we look at materials that can easily adsorb and effectively degrade these harmful KSAs, we see that the first studies were carried out using oxides of transition metals such as zirconium oxides, hydroxides or titanium oxides. However, an important disadvantage of these materials is their low surface area, low porosity, and poisoning of the active sites after the adsorption of KSA, which causes the catalyst to show low efficiency. Therefore, the use of zirconium-based metal-organic lattice structures (Zr-MOFs), as a class of crystalline organic porous materials with the high surface area and pores they provide, adds originality to the study. The development of MOF catalysts for the degradation of KSAs or simulants is very important, at least for laboratory-scale research. In this context; In this study, the catalytic hydrolysis efficiency for the degradation of dimethyl 4-nitrophenyl phosphate (DMNP), which is the simulant of Soman (GD) chemical warfare gas, was investigated. Catalytic hydrolysis activity kinetics for the degradation of dimethyl 4 nitrophenyl phosphate (DMNP), a KSA (GD (Soman)) simulant, were monitored by monitoring the formation of p-nitrophenoxide via UV–vis spectroscopy (?max = 407 nm). As a result of the study, it was seen that DMNP degraded with a more effective reaction at increasing temperature values, thanks to the Rh/UiO-66 catalyst. In addition, it was observed that when the amount of Rh/UiO-66 catalyst was increased, it degraded DMNP at higher rates and eliminated its toxic effect. Finally, due to the positive results obtained, it is thought that the Rh/UiO-66 MOF material used will provide an opportunity for integration into personal protective clothing or equipment (mask, clothing, etc.)
Hydrolysis of sodium borohydride catalyzed by graphitic carbon nitride-supported rhodium/iron nanoparticles
No full textBu çalışmada, grafitik karbon nitrür destekli RhFe nanoparçacıkları (RhFe/g-C3N4) emdirme-indirgenme yöntemine göre hazırlandı ve sodyum borhidrürün (NaBH4) hidroliz tepkimesinde katalizör olarak kullanıldı. Daha sonra elde edilen RhFe/g-C3N4 katalizörü ICP-OES, SEM, TEM, P-XRD, XPS gibi ileri spektroskopik yöntemler ile tanımlandı. Elde edilen bulgulara göre, en etkin Rh0.48Fe0.52/g-C3N4 katalizörünün çevrim frekansı (TOF) değeri 33.04 dak?¹ ve H? üretim hızı (HGR) 4214.02 mL·H?·dak?¹·gcat?¹ olarak hesaplandı. Ayrıca Rh0.48Fe0.52/g-C3N4 katalizörü tarafından katalizlenen NaBH4 hidroliz tepkimesinde aktivasyon parametreleri sırasıyla 66.20 (Ea#), 63.68 (?H#) ve -149.53 (?S#) olarak bulundu.NaBH4’ün hidroliz tepkimesinde Rh0.48Fe0.52/g-C3N4 katalizörü bir önceki çevrim sonrasında başlangıç katalitik etkinliğinin % 80.72’sini korumaktadır.In this study, graphite carbon nitride-supported RhFe nanoparticles (RhFe/g-C3N4) were prepared by the impregnation-reduction method and used as a catalyst in sodium borohydride (NaBH4) hydrolysis reaction. The obtained RhFe/g-C3N4 catalyst was then characterized by advanced spectroscopic techniques such as ICP-OES, SEM, TEM, P-XRD, and XPS. According to the findings, the cycle frequency (TOF) value of the most efficient Rh0.48Fe0.52/g-C3N4 catalyst was calculated as 33.04 min-¹ and H? production rate (HGR) was calculated as 4214.02 mL-H?-min-¹-gcat-¹. Moreover, the activation parameters for the NaBH4 hydrolysis reaction catalyzed by the RhFe/g-C3N4 catalyst were 66.20 (Ea#), 63.68 (?H#), and -149.53 (?S#), respectively. More importantly, in the hydrolysis reaction of NaBH4, the Rh0.48Fe0.52/g-C3N4 catalyst retains 80.72% of its initial catalytic activity after the previous cycle
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
PtCo/g-C3N4 bimetallic catalyst: Boosting hydrogen production in sodium borohydride hydrolysis
No full textDeveloping inexpensive and low-cost heterogeneous catalysts for hydrogen (H-2) release from chemical hydrogen storage materials such as sodium borohydride (NaBH4) is crucial for renewable, sustainable, and clean energy. For this purpose, we prepared an efficient bimetallic Pt0.77Co0.23/g-C3N4 catalyst for hydrogen production from the hydrolysis of NaBH4 and characterized it with advanced spectroscopic techniques, including inductively coupled plasma optical emission spectrometer (ICP-OES), powder X-ray diffraction (P-XRD), scanning electron microscope (SEM), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), and X-ray photoelectron spectroscopy (XPS). The H-2 released during the hydrolysis of NaBH4 was monitored through water displacement in a burette. The Pt0.77Co0.23/g-C3N4 catalyst exhibited a remarkable hydrogen generation rate (HGR) of 1373.1 mL min(-1) g(-1) at 298 K during NaBH4 hydrolysis. Additionally, the activation parameters were found to be 35.7 kJ/mol (Ea(#)), 38.9 kJ/mol (Delta H-#), and -119.6 J/molK (Delta S-#). Finally, the catalyst's recyclability performance was observed to retain >87.13 % of its catalytic conversion and >60.87 % of the catalytic activity even after the third recycling cycle
- …
