Современные концепции управления высшим учебным заведением

Целью и задачами статьи является исследование современных подходов к управлению вузом, их критический анализ и возможность оптимизации процессов деятельности вуза

Effect of the N content of Fe/N/graphene catalysts for the oxygen reduction reaction in alkaline media

In this work a series of N–modified graphene composites with different N/C ratios have been synthesised. The incorporation of Fe atoms into the N–modified graphene composites leads to the formation of Fe/N/C ensembles on the outer graphene layers along with Fe3C and metallic Fe phases in the bulk of the graphite nanoplates as revealed by X-ray absorption and XPS analyses. The adequate choice of the N/C atomic ratio of precursors to prepare Fe/N/graphene based materials is crucial to obtain electrocatalysts with an optimal performance for the ORR. The activity for the oxygen reduction reaction (ORR) of the Fe/N–graphene based electrocatalysts increases with increasing amount of accessible nitrogen, that is, with the amount of nitrogen by surface area.Peer Reviewe

Effect of N and S co-doping of multiwalled carbon nanotubes for the oxygen reduction

The co-incorporation of S and N into multiwalled carbon nanotubes (CNTs) and the effects for the catalytic performance for the oxygen reduction reaction (ORR) in acidic and alkaline electrolytes has been studied. Subjecting CNTs to different ballmilling periods results in the formation of defects in their graphitic structure. Heteroatoms such as N and S can be actually incorporated into such defects leading to active catalysts for the ORR. In fact, the ORR activity in acid and alkaline media increases with the increasing amount of heteroatoms, especially N, actually incorporated in the catalysts. The use of precursors containing both N and S into their structure such as thiourea, results in a higher incorporation of surface N atoms than with similar N-containing precursors. As a consequence the ORR activity of the S/N/CNTs based catalysts is higher than that of N/CNT ones. This promotional effect of the presence of S is more significant when the ORR is measured in alkaline media suggesting that S-incorporation into the carbon matrix could actually play a direct role for the ORR.This project was funded by the Deanship of Scientific Research (DSR), King Abdulaziz University, Jeddah, under grant number (D-006-432). The authors, therefore, acknowledge with thanks DSR technical and financial support. Economic support from project ENE2013-42322-R from the Spanish Ministry of Economy and Competitiveness is also acknowledged.Peer Reviewe

Influence of the electrolyte for the oxygen reduction reaction with Fe/N/C and Fe/N/CNT electrocatalysts

The behavior of Fe-based non-precious metal catalysts (NPMCs) in different electrolytes and the repercussion for the oxygen reduction reaction (ORR) has been studied. For this matter, a series of Fe-based NPMC electrocatalysts have been prepared from different carbon sources, carbon black and multiwalled carbon nanotubes. The catalysts have been subjected to chemical treatments in 0.5 M H2SO4 and thoroughly characterized. Their performance for the ORR in different electrolytes e.g. HClO4, H2SO4, CF3SO3H, KOH and NaOH has been studied. Higher ORR rates have been recorded in the alkaline electrolytes as compared to the acid ones. Remarkably, the effect of the electrolyte is almost negligible when measured at a given pH value; i.e., the ORR performance is not affected by the nature of the anion when measured in acid electrolytes or the cation when measured in alkaline electrolytes. On the other hand, the activity of NPMCs for the ORR decreases remarkably after treatment of the catalysts in 0.5 M H2SO4. This effect accounts to both the removal of active sites for the ORR during acid treatment and to the blockage of active sites due to the presence of adsorbed sulfates.This project was funded by the Deanship of Scientific Research (DSR), King Abdulaziz University, Jeddah, under grant number (D- 006-432). The authors, therefore, acknowledge with thanks DSR technical and financial support. Economic support from projects ENE2010-15381 from the Spanish Ministry of Science and Innovation and Project 201080E116 from the CSIC is also acknowledged.Peer Reviewe

On the relationship between N content, textural properties and catalytic performance for the oxygen reduction reaction of N/CNT

Non-precious metal catalysts for the oxygen reduction reaction (ORR) based upon the incorporation of different amounts of N into the CC network of multiwalled carbon nanotubes (CNTs) have been prepared by using CNTs and urea as the carbon and nitrogen sources, respectively. First, and with the aim of generating different levels of defects in the carbon network, the CNTs have been subjected to ballmilling during different periods of time between 0 and 150 h. Then, urea was mixed with the treated CNTs, subjected to further ballmilling and pyrolized at 800 °C. The number of defects, and as a consequence, the amount of N incorporated into the CNTs, increases with the duration of the ballmilling time. Moreover, the structure of the CNTs obtained after longer ballmilling times collapses leading to a carbon material with a high degree of microporisity. The performance of the N/CNT for the ORR, in terms of both the onset potential and mass current activity, increases with the amount of N actually incorporated into the CNT. Moreover, the H2O2 formation during ORR varies with the morphology of the catalyst. Thus, the formation of H2O2 is favored with the electrocatalysts in which the CNT structure is preserved, whereas the total reduction of O2 to H2O is favored for the electrocatalysts in which micropores are formed.This project was funded by the Deanship of Scientific Research (DSR), King Abdulaziz University, Jeddah, under grant number (D-006-432). The authors, therefore, acknowledge with thanks DSR technical and financial support. Economic support from Project 201080E116 from the CSIC is also acknowledged.Peer Reviewe

Influence of the Reaction Temperature on the Nature of the Active and Deactivating Species During Methanol-to-Olefins Conversion over H‑SAPO-34

The selectivity toward lower olefins during the methanol-to-olefins conversion over H-SAPO-34 at reaction temperatures between 573 and 773 K has been studied with a combination of operando UV–vis diffuse reflectance spectroscopy and online gas chromatography. It was found that the selectivity toward propylene increases in the temperature range of 573–623 K, while it decreases in the temperature range of 623–773 K. The high degree of incorporation of olefins, mainly propylene, into the hydrocarbon pool affects the product selectivity at lower reaction temperatures. The nature and dynamics of the active and deactivating hydrocarbon species with increasing reaction temperature were revealed by a non-negative matrix factorization of the time-resolved operando UV–vis diffuse reflectance spectra. The active hydrocarbon pool species consist of mainly highly methylated benzene carbocations at temperatures between 573 and 598 K, of both highly methylated benzene carbocations and methylated naphthalene carbocations at 623 K, and of only methylated naphthalene carbocations at temperatures between 673 and 773 K. The operando spectroscopy results suggest that the nature of the active species also influences the olefin selectivity. In fact, monoenylic and highly methylated benzene carbocations are more selective to the formation of propylene, whereas the formation of the group of low methylated benzene carbocations and methylated naphthalene carbocations at higher reaction temperatures (i.e., 673 and 773 K) favors the formation of ethylene. At reaction temperatures between 573 and 623 K, catalyst deactivation is caused by the gradual filling of the micropores with methylated naphthalene carbocations, while between 623 and 773 K the formation of neutral poly aromatics and phenanthrene/anthracene carbocations are mainly responsible for catalyst deactivation, their respective contribution increasing with increasing reaction temperature. Methanol pulse experiments at different temperatures demonstrate the dynamics between methylated benzene and methylated naphthalene carbocations. It was found that methylated naphthalene carbocations species are deactivating and block the micropores at low reaction temperatures, while acting as the active species at higher reaction temperatures, although they give rise to the formation of extended hydrocarbon deposits

Effect of carbon nanotube diameter for the synthesis of Fe/N/multiwall carbon nanotubes and repercussions for the oxygen reduction reaction

The effect of the diameter of multiwalled carbon nanotubes for the incorporation of N and Fe and the consequences for the oxygen reduction reaction in acid medium has been studied. For this, a series of multiwalled carbon nanotubes with mean diameters of 10, 20 and 60 nm have been thermally treated in acid media and modified by addition of N- and Fe-groups by means of thermal treatments under inert atmosphere. The chemically treated nanotubes and the FeN-CNTs have been thoroughly characterized by N2 adsorption/desorption isotherms, Raman spectroscopy, X-ray photoelectron spectroscopy, elemental analysis, thermogravimetric analysis and X-ray diffraction. The performance of the FeN-CNTs for the oxygen reduction reaction (ORR) in acid medium has been evaluated by means of electrochemical techniques. We have found that the amount of nitrogen actually incorporated onto the multiwalled carbon nanotubes, which ranges between 2 and 3 wt.%, can be directly related with the number of defects of the chemically treated multiwalled nanotubes. On the other hand, the BET specific surface area of the FeN-CNTs increases with the decreasing diameter of the CNTs. A direct relationship between the nitrogen external surface area and the ORR performance has been observed.This project was funded by the Deanship of Scientific Research (DSR), King Abdulaziz University, Jeddah, under grant number (D-006-432). The authors, therefore, acknowledge with thanks DSR technical and financial support. Economic support from projects ENE2010-15381 from the Spanish Ministry of Science and Innovation and Project 201080E116 from the CSIC is also acknowledged.Peer Reviewe