Activation of NO2 by Modifying the Porphyrin Unit with Oxygen in a MnN4 Graphene Layer

In this article, the activation of N−O bonds in NO2 molecules has been investigated by Density Functional Theory (DFT) calculations. Considering the graphene-based MnN4 layer, nitrogen atoms in the porphyrin unit were sequentially replaced with oxygen atoms to create different MnNmOn/G (m+n=4 and 1<m≤4) layers. As more oxygen atoms are incorporated in porphyrin units for bare layers, the covalent character of the Mn−O bonds is switched to the transit nature with respect to Mn−N bonds. Moreover, the trend in bond strength decreasing in all oxygen-containing bonds is in line with the formation energy trends of bare layers. The same situation is also valid for the bonds between Mn−N/O. For NO2 adsorption configurations on all MnNmOn/G layers, N−O bonds in NO2 are weakened by populating/depopulating antibonding/bonding orbitals, respectively. Even if the MnN2O2(hex)/G layer has a moderate NO2 adsorption energy among the other layers, this layer provided the most significant activation over N−O bonds based on crystal orbital Hamilton population (COHP), crystal orbital bond index (COBI), and Atoms in Molecules (AIM) Bader Topological Analysis. Our results show that integrated COHP and integrated COBI values show a remarkable correlation with AIM-Bader parameters for the specific bonds which have descriptive capability over NO2 molecule activation

The Effect Of The Solıd Catalysts To The Hydrolysıs Of The Metal Borohydrıdes

Bu tezde, sodyum ve lityum borhidrür hidroliz reaksiyonları bazı altın yüzeyleri üzerinde incelenmiştir. Reaksiyon yolu, reaksiyondaki toplam atom sayısı korunacak şekilde H2O molekülü ve H2 gazı ile ·OH radikallerini içerecek şekilde oluşturulmuştur. İlk kısımda, reaksiyon yolunda reaksiyon ara durumlar kübik bir kutunun içerisine konularak elektronik toplam enerjileri hesaplanmıştır. Daha sonra ara durumların yüzeylerle etkileşmeleri sağlanmıştır. Bu noktada, ·OH radikalleri vakum ortamı içerisinde kalacak ve yüzeylerle etkileşecek şekilde iki farklı yol izlemiştir. Göreli enerji diyagramına göre ·OH radikallerin yüzeylerle etkileşmesi gerektiği sonucuna varılmıştır. İkinci kısımda, ara durumlar arası geçiş durumları LSG/QSG algoritması ile elde edilmiştir. Tüm geçiş durumları ve enerjileri altın yüzeyleri katalitik aktivitelerine göre sınıflandırılmıştır. Hesaplamalar göstermiştir ki, Au(210) yüzeyi NaBH4 hidroliz reaksiyonu için göreli enerji diyagramı yoluyla gözlemlenen endotermik kısımlarda oldukça etkindir. Son olarak, NaBH4 hidroliz reaksiyonu Au(210) yüzeyi üzerinde LiBH4 hidroliz reaksiyonuna göre daha kolay gerçekleştiği bulunmuşturIn this thesis, sodium and lithium borohydride (NaBH4 and LiBH4) hydrolysis reactions have been investigated on some single crystal gold surfaces. The reaction pathway have been formed including H2 gas, H2O molecules and ·OH radicals through the total number of the atoms are conserved. Firstly, reaction intermediates in reaction route were placed in a cubic box and electronic total energies were calculated. Then, these reaction intermediates were allowed to interact with the catalytic surfaces. At this point, two different scheme were adopted which are ·OH radicals are left in vacuum and to interact with the surfaces. It was concluded that ·OH radicals should interact with the surfaces according to the relative energy diagram obtained both these two schemes. In the second part, the transition state calculations were made by LST/QST algorithm. All transition state energies and structures were determined to order gold surfaces with reference to their catalytic activities. It was found that Au(210) surface generally is more active than the other surfaces for the endothermic part of the reaction route found by relative energy diagram at first round for NaBH4 hydrolysis reaction. Finally, it was found that NaBH4 hydrolysis reaction takes place easier on Au(210) than LiBH4 hydrolysis reactio

Investıgatıon Si(100) surface usıng 2-dımensıonal ısıng model

Bu çalışmada, Si(100) yüzeyinin kritik davranışı Ising modeli temel alan Creutz Cellular Automaton soğutma algoritması ile incelenmiştir. Hesaplamalar, periyodik sınır koşulları göz önüne alınarak, Lx=30, 60, 90, 120 ve Ly=Lx, 2Lx,&#8230;.,10Lx kenar uzunluklu dikdörtgen örgüler kullanılarak yapılmıştır. İncelemeler, Si(100) yüzeyindeki dimerlerin anizotropik etkileşimlerinden dolayı düzen durumunu elde etmek için gerekli en büyük Lx/Ly oranının 1/7 olması gerektiğini göstermiştir. Ayrıca yüksek sıcaklıkta STM gözlemleriyle uyumlu yüzey resimleri elde edebilmek için spin ortalamalarının belirli bir &#8486; ayrıma oranıyla ayrılması gerektiği sonucuna varılmıştır. Farklı parametre setlerine ait sonsuz örgü kritik sıcaklıkları elde edilmiş, deneysel ve teorik sonuçlarla karşılaştırılmıştır. Son olarak, diagonal parametre değişiminin kritik davranışa etkisi gösterilmiştir.In this study, critical behaviour of Si(100) surface is intestigated by using cooling algorithm which is improved from Creutz Cellular Automaton based on Ising Model. The simulation are carried on rectangular lattice with linear dimensions Lx=30, 60, 90, 120 and Ly=Lx, 2Lx,&#8230;.,10Lx using periodic boundary conditions. The investigations showed that maximum Lx/Ly proportion due to dimer-dimer anisotropic interactions must be 1/7 to obtain ordered phase. Furthermore, in order to get compatible surface reconstructions with STM results at high tempratures, spin average must be seperated with seperation proportion, &#8486;. Infinite lattice critical temperatures corresponding to different parameter sets are obtained and compared with experimental and theoretical results. Finally, we show that variation of diagonal interaction parameter is effective on critical behaviour

The catalytic effect of the Au(111) and Pt(111) surfaces to the sodium borohydride hydrolysis reaction mechanism: A DFT study

WOS: 000441493800027In this research, hydrolysis mechanism of sodium borohydride (NaBH4) have been studied theoretically on Au (111) and Pt (111) noble metal surfaces by periodic density functional theory calculations. Elementary reaction steps have been generated based on study of borohydride oxidation. Reaction intermediates which have plethora of hydroxyl (OH center dot) radical(s) have been produced by decomposition of water molecule(s). In order to investigate surface effect, we have followed two different routes. The first route is that the atomic and molecular structures in the reaction steps have been optimized in 3-d box without a catalyst. At second one, they were interacted with the Au (111) and Pt (111) surfaces to compare relative behavior with reference to the non-catalytic medium. The relative energy diagrams were produced by relative energy differences which is useful to generate energy landscape using required/released energies in order to pursue the reaction. Three main peaks that means considerable energy changes have been observed to proceed the reaction in the non-catalytic medium. Then, changes in the energy differences depending on surfaces have been discussed. Although acquired relative energies are not within chemical accuracy, they are very successful to show the affect of the OH radical concentration to the potential energy diagram. Pt (111) surface have been found more reactive than Au (111) surface for Sodium Borohydride Hydrolysis reaction, as it is obviously coherent with the literature

Hydrazine decomposition on nickel-embedded graphene

*Akça, Aykan ( Aksaray, Yazar )In this article, the catalytic effect of the Ni-embedded graphene has been investigated for hydrazine (N2H4) decomposition reaction through Density Functional Theory (DFT) calculations with Grimme-D2 dispersion correction. Nickel embedded graphene systems are expected to be much cheaper than pristine nickel surfaces in the future because of relatively few numbers of Ni atom usage, experimentally synthesizable, and limit the Ni usage. The transformation of N2H4 has been taken into account in two different ways. The first way is sequential N–H and, the second one is the N–N bond cleavage from the gauche conformation which is the most stable conformation in gas phase and sole conformation observed on the Ni site. According to our findings, ·NH2 formation breaking the N–N bond in hydrazine has lower activation energy than hydrogen abstraction from hydrazine. The difficulty of breaking N–H bonds stems from the spatial accumulation of negative and positive charges, so it causes a mismatch between hydrogen atoms and negatively charges carbon atoms. NH3 formation pathway through the interaction of N2Hx (x = 1 → 4) species with co-adsorbed ·NH2 radicals is accompanied by much lower activation barriers and highly exothermic. Nevertheless, metal-embedded graphene systems are promising materials for hydrazine dehydrogenation and can be tailored to have more efficient charge distributio

Pre- and Post-Operative Hamstring Autograft ACL Reconstruction Isokinetic Knee Strength Assessments of Recreational Athletes

Background and Objectives: Anterior cruciate ligament (ACL) injuries are common injuries with a high incidence among people with high physical activity levels. Therefore, ACL reconstruction (ACLR) is one of the most common surgical procedures performed in sports medicine. This study aims to compare the pre- and 6-month post-operative isokinetic knee strengths in healthy (HK) and ACL knees of patients who underwent semitendinous/gracilis (ST/G) ACLR. Materials and Methods: A retrospective cohort of 21 recreational athletes who underwent ST/G ACLR by the same surgeon were evaluated. The pre- and 6-month post-operative isokinetic knee extension (Ex) and flexion (Flx) strengths of the HK and ACLR patients were evaluated in a series consisting of three different angular velocities (60, 180 and 240°/s). Of all the findings, peak torque (PT) and hamstring/quadriceps (H/Q) parameters were evaluated. Results: There was a significant improvement in post-operative Lysholm, Tegner and IKDC scores compared to pre-operative scores (p p p > 0.05). As for H/Q ratios, there was a significant difference between pre- and post-operative values only at 60°/s angular velocity in both ACLR and HC (p < 0.005). Conclusions: The pre-operative and 6-month post-operative results of the ST/G ACLR showed that there was a high level of recovery, particularly in quadriceps strength, while the increase in strength was less in the hamstring. The significance observed at 60°/s in H/Q ratios was within normal ranges. It can be argued that the ST/G ACLR method is feasible for people with high physical activity levels and for athletes

Photodeposition of molybdenum sulfide on MTiO3 (M: Ba, Sr) perovskites for photocatalytic hydrogen evolution

Photocatalytic hydrogen evolution using by semiconductor materials have been studied effectively by converting solar energy into the chemical energy. Perovskite-based materials have been widely used as semiconductor catalysts for the photocatalytic hydrogen production. Herein, molybdenum sulfide photodeposited onto MTiO3 (M: Ba, Sr) perovskites (MTiO3/MoSx) have been investigated on the photocatalytic hydrogen evolution under solar light irradiation in the presence of triethanolamine (TEOA) and eosin Y (EY) as an electron donor and photosensitizer, respectively. Compared to pristine MTiO3, BaTiO3/MoSx and SrTiO3/MoSx show a remarkable improvement in the hydrogen production efficiency and stability. Photocatalytic hydrogen evolution activities found in the order of SrTiO3/MoSx > BaTiO3/MoSx > MoSx > SrTiO3 > BaTiO3. In addition, photocatalytic hydrogen activity of SrTiO3/Pt was evaluated for comparison with SrTiO3/MoSx under the same conditions and SrTiO3/MoSx produced higher hydrogen activity than SrTiO3/Pt due to the high active sites created by MoSx on the catalyst surface which is originated from Mo–S and S[sbnd]S bond

Ammonia free catalytic reduction of nitric oxide on Ni-embedded graphene nanostructure: A density functional theory investigation

In this study, the catalytic reduction reaction of NO (directly) without the presence of ammonia (NH3) was studied on the Ni-embedded graphene (Ni@GN) layer using periodic Density Functional Theory (DFT) calculations. Ni-embedded graphene surface can be synthesized experimentally and it is predicted that it will cost much less than single crystal surfaces due to the economic usage of the transition metal atoms. First of all, by optimizing the geometric structure of the Ni@GN layer, crucial geometric features and electron density differences (EDD) were obtained. Based on the different adsorption configurations of NO molecule, the reduction reaction was investigated by Langmuir-Hinshelwood (L-H) and Eley-Rideal (E-R) based mechanisms. Finally, N2O degradation was analyzed in detail. It is shown that the Eley-Rideal model is a more dominant mechanism on the Ni@GN surface than the other model. In addition, all proposed reaction pathways for NO reduction are exothermic. This information can be used for the research and development of graphene-based materials for NO reduction; paves the way for finding new Ni-based catalysts based on active single transition metal atom embedded on different kind of defects