Doctor of Philosophy / Department of Physics / Talat S. Rahman / In this work we present a study of the geometric, electronic, vibrational and magnetic properties of several nanostructured systems for which experimental data call for a theoretical understanding. In order to investigate the effect of magnetic dipolar interactions on the magnetization of nanomagnets arranged in finite lattices, we utilize a phenomenological classical approach, which is based on the Landau-Lifshitz equation. Dipolar interactions lead to hysteretic behavior of the magnetization curves and established that the external field sweep rate, sample temperature, and shape anisotropy play a role in determining the specifics. Our results (derived from a classical approach) for magnets arranged in a square lattice suggest that stepped hysteresis curves do not have necessarily a quantum origin (quantum tunneling of the magnetization). We also find that in the square lattice small changes in the dipolar strength introduce sudden transitions in the magnetic hysteresis. For the examination of geometric vibrational and electronic structure of systems of interest, we turn to density functional theory (DFT), which is the leading technique for modeling nanoscale systems from first principles. We have applied DFT to either address some old queries of surface science, such as the dynamics of the CO-chemisorbed Cu(001) surface, or to contribute to the forefront of hydrogen-based economy through the comprehension of the growth and diffusion of Pt islets on Ru(0001), or to predict the geometric and electronic properties of materials to-be-created, as in the case of core-shell bimetallic nanoclusters. In the case of CO on Cu(001), although the bond has been considered to be weak enough so as to treat the adsorbate and substrate separately, our calculations are able to reproduce measurements and provide evidence that the dynamics of the molecule is influenced by the substrate and vice versa, as well as by intermolecular interactions. Taking into account the adsorbate-substrate interplay, has furthermore clarified issues that were pending for the clean surface and led to the correct interpretation of some features in the phonon dispersion of the chemisorbed surface. DFT has also directed us to the conclusion that the catalytic properties of few-atom Pt islets on Ru nanoclusters are preserved by the low probability of these islets to diffuse through the edges of the Ru nanoclusters. Moreover, the analysis of the Ag_{27}Cu_7 nanoalloy from ab initio methods has opened a wide panorama in terms of the geometry, coordination, energetics, and electronic structure of alloyed phases, in general,that may aid in the assembling on new materials.

In Canada’s western Arctic, perennial discharge from permafrost watersheds is the surface manifestation of active groundwater flow systems, yet understanding the mechanisms of groundwater recharge and flow in periglacial environments remains enigmatic. This thesis addresses questions on how and where groundwater recharge occurs. Watersheds were selected in Yukon (Fishing Branch River at Bear Cave Mountain) and the Northwest Territories at latitudes spanning from continuous to discontinuous permafrost (five tributary rivers to the Mackenzie River from Wrigley to Aklavik). All are characterized by perennial flow with open water in the winter, and discharge from sedimentary formations of karstic carbonates and evaporate rocks. Determinations of groundwater contributions to discharge, mixing, recharge conditions and circulation times were made on the basis of a suite of analytical approaches involving measurements of major dissolved ions, δ18O, δD, δ13CDIC, 3H, noble gases and flow gauging was conducted at some sites. The application of these tracers show that hydrogeological conditions and flow paths in permafrost terrains are surprisingly similar to those of temperate regions. Groundwater recharge was determined to be a mix of annual precipitation with contributions from snowmelt and precipitation. All systems investigated show that groundwaters have recharged through organic soils with elevated PCO2, which suggests that recharge occurs largely during summer when biological activity is high. Noble gas concentrations show that the recharge temperature was between 0 and 6 °C, which, when considered in the context of discharge temperatures, suggests that there is no significant imbalance of energy flux into the subsurface. Groundwater ages were found using the 3H-3He method and were dependent on flow path. By characterizing groundwater and surface water chemistry, the proportion of groundwater was found in numerous water courses. The possible impact of ground ice formation and melting on noble gas concentrations in groundwater was considered. To assess this link, a new method to measure the noble gas composition of ground ice bodies was developed. The method can be used to determine the origin of ice, based on changes in noble gas ratios between ice originating from compaction of snow (e.g. glacier ice) vs. ice originating from freezing of water. No significant fractionation of noble gases during groundwater freezing and ground ice formation was identified. Applied to determination of the origin of ground ice bodies, the method was shown to be both diagnostic of ice origin and un-encumbered by reactivity in the subsurface, which compromises the use of the dominant atmospheric gases (O2 and N2).   Résumé Dans l’Ouest de l'Arctique canadien, la décharge pérenne dans certaines rivières en région de pergélisol est la manifestation en surface d’une circulation d’eau souterraine; cependant la compréhension des mécanismes d’écoulement et de recharge des eaux souterraines en région de pergélisol demeure énigmatique. Cette thèse s’intéresse à la question de savoir comment et où la recharge des eaux souterraines se produit. Des bassins versants ont été choisis au Yukon (Rivière Fishing Branch à Bear Cave Mountain) et dans les Territoire du Nord-Ouest à des latitudes s’étendant du pergélisol discontinu au pergélisol continu (cinq tributaires du Mackenzie entre Wrigley et Aklavik). Toutes ces rivières ont un écoulement d’eau pérenne avec des zones non gelées et une décharge dans des formations sédimentaires de roches carbonatées et d‘évaporites. L’identification des contributions des eaux à la décharge, les mélanges, les conditions de recharge, et les temps de circulation ont été faits à partir d’analyses qui ont inclus les concentrations en éléments majeurs, leur valeur isotopique (δ18O, δD, δ13C, 3H), ainsi que leur teneur en gaz rares. A certain des sites analysés des mesures d’écoulement ont été prises. L’application de ces traceurs montre que les conditions hydrauliques et le chemin des écoulements en région de pergélisol sont similaires à ceux des régions tempérées. La recharge en eau souterraine a été identifiée comme étant un mélange de précipitations annuelles, avec des contributions de neige et de pluies. Tous les systèmes étudiés montrent que les eaux souterraines se sont rechargées en traversant des sols organiques avec une PCO2 élevée, ce qui suggère que la recharge se produire largement durant l’été quand l’activité biologique est élevée. Cependant, les concentrations en gaz nobles montre que la température de recharge des eaux souterraines était entre 0 et 6 °C ce qui indique qu’il n’y a pas de déséquilibre de flux d’énergie à l’intérieur de la zone proche de la surface. L’âge des eaux a été déterminé par la méthode 3H-3He et cet âge est dépendant du chemin d'écoulement. En caractérisant les paramètres chimiques des eaux de surface et des eaux souterraines, il a été possible de trouver la contribution des eaux souterraines aux eaux surface. Le possible impact de la formation et de la fonte de la glace souterraine sur les concentrations des gaz nobles a été considéré. Pour déterminer s’il y a un lien entre ceux-ci, une nouvelle méthode pour mesurer la concentration en gaz nobles dans les glaces souterraines a été développée. La méthode peut être utilisée pour déterminer l’origine de la glace; elle est basée sur les changements dans les rapports des gaz nobles entre la glace issue de la compaction de la neige (c’est-à-dire la glace de glacier) par opposition à la glace issue du gel de l’eau. Aucun fractionnement significatif des gaz nobles durant l’engel des eaux souterraines et la formation de glaces souterraines n’a été identifié. Appliquée à l’identification de l’origine des masses de glace enfouies, on a montré que la méthode pouvait permettre d’identifier l’origine des glaces souterraines sans qu’elle soit affectée par des réactions biologiques de sub-surface, lesquelles rendent inutilisables les gaz atmosphériques (O2, and N2).

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Dans le contexte des écoulements micro- et nano-fluidiques, ce travail porte sur l'étude des interactions à l'interface entre des flux de gaz rares et des surfaces métalliques via une approche de modélisation multi-physique et multi-échelle. Elle se concentre tout particulièrement sur l'interaction entre l'argon et une surface d'or. Pour ce faire la modélisation a été effectuée en deux étapes, une première partie utilisant la mécanique quantique à l'échelle atomique et une deuxième partie de dynamique moléculaire à l'échelle nanométrique. La première partie est consacrée à l'obtention de potentiels d'interaction entre un atome d'argon et les atomes d'or de la surface par des méthodes de calculs théoriques basés sur la DFT comportant des effets à longues distances. Deux approches, donnant des résultats comparables, ont été utilisées : la première est liée à la description périodique de la surface d'or par un modèle basé sur la description des électrons par des ondes planes alors que la seconde permet de récupérer séparément les parties répulsives et attractives de l'interaction d'un atome d'argon avec un petit cluster d'or. Ces potentiels d'interactions ont été décomposés en potentiels de paires Ar-Au utilisables par des simulations de dynamique moléculaire. Ces simulations ont consisté en la projection d'atomes d'argon sur des surfaces d'or ‘parfaites' dites lisses ou des surfaces rugueuses plus représentatives de la technologie actuelle. L'analyse statistique des vitesses réfléchies permet de déterminer le coefficient d'accommodation tangentiel de l'argon sur des surfaces d'or. Ce coefficient est la traduction du phénomène de glissement qui peut ainsi être modélisé dans une description plus macroscopique de l'écoulement d'un gaz dans une micro-conduite. L'approche multi-physique utilisée dans ce travail a permis la détermination numérique de coefficients d'accommodations tangentiels très précis et comparables à l'expérience pour le couple argon-or, et doit pouvoir être appliquée à d'autres couples / In the context of micro- and nano-flows, this work concentrates on the study of interactions at the interface of noble gas and metal surfaces by a multi-physics and multiscale model. Particularly, the interaction of an argon atom with a gold surface is the focus of the study. The work has been made in two steps: the first one occurred at the atomic scale in which Quantum Mechanics is employed and the second one at the nanoscale with the use of Molecular Dynamics.The first part of the work was devoted to the determination of interaction potentials between an argon atom and gold atoms from the surface by DFT calculation methods comporting long range effects. Two approaches, leading similar results, have been used: the first one is linked to a periodic description of the gold surface where electrons are defined by plane waves, the second one gives independently repulsive and attractive parts of the interaction of an argon atom with a small gold cluster. Those interaction potentials are then decomposed in pair potentials suitable for Molecular Dynamics simulations. These last ones consisted in multiple times projecting argon atoms on smooth or rough gold surfaces (which are more representative of the roughness of actual technologies). The statistical analysis of the reflected velocities yielded the tangential momentum accommodation (TMAC) coefficient of argon on gold surfaces. This coefficient is the transcription of slip phenomena which occur at the interface, and it can then be used in nano-flow simulations. The multi-physics approach of the thesis gives accurate TMAC values which are comparable to experiments. The accounted method could then be applied to other noble gas metal surface couples

A number of recent successful authorship studies have relied on a statistical analysis of language features based on function words. However, stylometry has not been extensively applied to Elizabethan and Jacobean dramatic questions. To determine the effectiveness of such an approach in this field, language features are studied in twenty-four plays by Shakespeare and eight by Fletcher. The goal is to develop procedures that might be used to determine the authorship of individual scenes in The Two Noble Kinsmen and Henry VIII. Homonyms, spelling variants and contracted forms in old-spelling dramatic texts present problems for a computer analysis. A program that uses a system of pre-edit codes and replacement /expansion lists was developed to prepare versions of the texts in which all forms of common words can be recognized automatically. To evaluate some procedures for determining authorship developed by A. Q. Morton and his colleagues, occurrences of 30 common collocations and 5 proportional pairs are analyzed in the texts. Within-author variation for these features is greater than had been found in previous studies. Univariate chi-square tests are shown to be of limited usefulness because of the statistical distribution of these textual features and correlation between pairs of features. The best of the collocations do not discriminate as well as most of the individual words from which they are composed. Turning to the rate of occurrence of individual words and groups of words, distinctiveness ratios and t-tests are used to select variables that best discriminate between Shakespeare and Fletcher. Variation due to date of composition and genre within the Shakespeare texts is examined. A multivariate and distributionfree discriminant analysis procedure (using kernel estimation) is introduced. The classifiers based on the best marker words and the kernel method are not greatly affected by characterization and perform well for samples as short as 500 words. When the final procedure is used to assign the 459 scenes of known authorship (containing at least 500 words)almost 112 95% are assigned to the correct author. Only two scenes are incorrectly classified, and 4.8% of the scenes cannot be assigned to either author by the procedure. When applied to individual scenes of at least 500 words in The Two Noble Kinsmen and Henry VIII, the procedure indicates that both plays are collaborations and generally supports the usual division. However, the marker words in a number of scenes often attributed to Fletcher are very much closer to Shakespeare's pattern of use. These scenes include TNK IV.iii and H8 I.iii, IV.i-ii and V.iv.

La société nobiliaire des pays de la Couronne de Bohême connut à compter de 1620 et jusqu’au milieu du XVIIe siècle de considérables transformations. La modification radicale de sa structure fut en partie liée à l’arrivée des nouvelles familles dont la majorité appartenaient à la noblesse germanophone. Or, ces lignées ne furent pas les seules à chercher la carrière ou la fortune au service de l’Empereur. Nous y vîmes également de nombreux Espagnols, Irlandais et Ecossais, des nobles originaires des Pays-Bas espagnols ou encore des lignages francophones. Ces derniers provenaient d’une large zone géographique comprenant la Bourgogne, la Provence, l’Artois, le Hainaut français dont la ville de Cambrai, la Lorraine pour en terminer par la Savoie. En effet, ce genre du phénomène migratoire eut des contours assez étendus et se limiter aux seuls Français impliquerait de ne pas prendre en considération le fait que la langue et la culture comptaient davantage que l’origine. Mais il n’existe aucune synthèse ni d’étude analytique sur cette forme de migration dont bien des aspects restent encore négligés et tout simplement à étudier. L’objectif du présent travail fut de présenter un destin particulier d’un noble établi dans les pays tchèques – dans le Margraviat de Moravie en l’occurrence – celui de Jean Louis Ratuit de Souches (1608-1682). Contemporain des grandes personnalités militaires de l’époque, telles que le Grand Condé, Raimondo Montecuccoli, Gustave-Adolphe ou encore Turenne, connues davantage, Jean Louis Ratuit de Souches accomplit, lui aussi, des exploits dignes d’être relatés. Né à La Rochelle, dans un milieu de la petite noblesse huguenote, il sut bâtir sa carrière au service des Habsbourg. Soldat, il se battit successivement pour défendre la cause du protestantisme, d’abord à La Rochelle, sa ville natale, contre les troupes de Louis XIII, ensuite dans l’armée suédoise contre les impériaux. Plus tard, il devint général de Ferdinand III, puis de Léopold Ier, en se servant de ses connaissances de la tactique adverse pour lutter contre les Suédois et les Français. Parti d’un milieu modeste, il finit par être reconnu comme un des plus grands chefs militaires de l’époque et accumula une fortune considérable ce qui lui valut les éloges des uns mais également les critiques et les réactions de jalousie exacerbées, aussi bien dans l’armée qu’à la cour viennoise.Afin de réussir son intégration dans le nouveau milieu, Jean Louis Ratuit de Souches se convertit et pour prouver la profondeur de sa foi, il alla même jusqu’à la fondation d’un lieu de pèlerinage sur ses domaines moraves. Contrairement à beaucoup de ses compatriotes, il laissa des traces durables dans l’histoire du pays et sa légende continua à vivre même après sa mort : un nombre de contes, œuvres d’art et monuments de tout genre allant jusqu’aux fêtes commémoratives en témoignent suffisamment. Pourtant, aujourd’hui encore, une partie non négligeable des épisodes de sa vie privée et publique reste ignorée.Au cours de nos recherches, nous avons également élaboré un catalogue de fiches biographiques et bibliographiques portant sur les familles francophones installées dans les pays de la Couronne de Bohême dans les années 1618-1740. Il permet ainsi une orientation basique dans ce phénomène migratoire spécifique et pourrait servir de point de départ pour des éventuels travaux futurs. / Noble society in the Lands of the Bohemian Crown knew from 1620 to the 1650’s considerable transformations. The radical change in its structure was in part linked to the arrival of new families from mostly German speaking nobility. These families weren’t the only ones to look for career and fortune at the service of the Emperor. There were also many Spanish, Irish and Scottish noble families, the families that came from Spanish Holland and the French lineages. These ones originated from an important geographical area containing French regions of Burgundy, Provence, Artois and Hainaut with the town of Cambrai, Lorraine and going up to Savoy. Indeed, this type of migratory phenomenon extended largely its boundaries and we cannot limit the study to only the French because the culture and language were more important than origin. Yet, there is no analytical study of this type of migration and it remains widely neglected. The purpose of this study was to show the particular destiny of one nobleman in the Czech Crown Lands (specifically in the Margraviat of Moravia), Jean Louis Ratuit de Souches (1608-1682). Being a contemporary of the great and better-known military celebrities, such as Le Grand Condé, Raimondo Montecuccoli, Gustave-Adolphe or Turenne, Jean Louis Ratuit de Souches also accomplished great feats that must be studied. Born into small Huguenot nobility in La Rochelle, he pursued a career at the service of the Habsburgs. As a soldier, he often fought for the protestant cause, first in La Rochelle, his hometown, against the troops of Louis 13th, then with the Swedish army against the imperials. Later on, he became one of Ferdinand 3rd ’s general, then one of Leopold 1st ’s by using his knowledge of the enemy’s tactics to fight the Swedish and the French. Although he came from a modest household, he rose to be considered as one of the greatest military leaders at the time and amassed a considerable fortune earning him much respect but also criticism and jealousy from the Army and the Viennese Court. To be a part of this new milieu, Jean Louis Ratuit de Souches converted and to prove his faith, he even constructed a place of pilgrimage on his Moravian lands. Contrary to many of his fellow citizens, he deeply influenced the country’s History and his legend lived on after his death: there are countless stories, paintings and all kinds of monuments and festivities in his honor. However yet today, a lot of his personal and public life still unknown. These studies have also given a chance to conceive a catalog of biographical and bibliographical archives regarding the French speaking families that lived in the Lands of the Bohemian Crown between 1618 and 1740. The catalog guides us through this particular migratory phenomenon and may be the starting point of future studies.

Como sabemos, as reflexões do filósofo político e contratualista Jean-Jacques Rousseau tornaram-se referência para muitos escritores que o sucederam, principalmente no que concerne às suas considerações a propósito da vida em sociedade, ambiente vil que degenera o homem, ser bom e piedoso por natureza. Tratase do célebre conceito rousseauniano do bom selvagem, teoria cuja repercussão pode ser encontrada em obras de muitos autores do período oitocentista, entre as quais podemos destacar a do romancista francês Honoré de Balzac e a do ficcionista português Camilo Castelo Branco. Isto porque, a partir de um estudo comparativo realizado entre volumes balzaquianos e camilianos, levantou-se a hipótese de que estes escritores, ao tecerem suas críticas sociais, dialogam com a mencionada teoria de Rousseau, muito embora cada um o faça a seu modo e finde por concatenar mundividências literárias distintas, únicas e inovadoras, que particularizam, de forma marcante, ambos os cânones ficcionais. Assim posto, e levando em consideração a ausência de estudos críticos a esse respeito, nosso intento é o de analisar uma questão inédita no que concerne à comparação entre a ficção balzaquiana e a camiliana: a diferente concepção que os respectivos narradores apresentam acerca dos efeitos sociais no homem, a partir de um diálogo estabelecido por ambos com o conceito rousseauniano do bom selvagem. Vale ressaltar que o estudo comparativo aqui proposto seguirá alguns pressupostos básicos da Literatura Comparada, sendo o principal deles a busca pelas particularidades de cada literatura (Cf. ABDALA Jr., 2003). / As we know, the reflections of the political and contractualist philosopher Jean- Jacques Rousseau became reference for many writers who succeeded him, mainly as concerns the considerations regarding the life in society, a vile ambience that degenerates man, a good and pious living being by nature. This is the renowned Rousseaunian concept of the noble savage, theory that can be found reverberated in many works of 19th century authors, among which we can highlight the one of the French novelist Honoré de Balzac and the one of the Portuguese fictionist Camilo Castelo Branco. That is because, from a comparative study realized between Balzacian and Camilian works, we hypothesized that these writers dialogue, as they construct their social criticisms, with the mentioned Rousseaus theory, although each one does it in his own way and ends by concatenating distinct literary worldviews, unique and innovative, that particularize, markedly, both of the fictional canons. Therefore, and taking into consideration the absence of critical studies regarding this, our intent is to analyze an unprecedented issue concerning the comparison between Balzacian and Camilian fiction: the different conception the narrators present about the social effects in man, through a dialogue established by both of them with the Rousseaunian concept of the noble savage. It is worth to stress that the comparative study proposed here will follow some basic assumptions of Comparative Literature, the main one being the research for the particularities of each literature. (Cf. ABDALA Jr., 2003).

Este trabalho teve como objetivo investigar eletrocatalisadores de baixo custo à base de carbeto de tungstênio, carbono e ferro submetidos a diferentes processos de nitretação quanto à atividade catalítica para reação de redução do oxigênio (RRO) nos eletrólitos ácido e alcalino. Os catalisadores foram divididos em três séries distintas, a primeira compreendendo aqueles onde houve variação da carga de carbeto de tungstênio em relação ao suporte de carbono, que foram impregnados com o complexo Fe2+(2,4,6-Tris(2-piridil)-1,3,5-Triazina)2, [Fe(TPTZ)2]2+ e tratados em duas temperaturas diferentes, 700 e 800 oC em atmosfera de nitrogênio. Na segunda série foi mantida constante a carga de carbeto de tungstênio (30% de W/C, m/m) sendo que esta mescla foi preparada usando carbonos dopados previamente com três fontes distintas de nitrogênio (HNO3, NH3 e HNO3/NH3); isto foi seguido pela incorporação do complexo Fe[TPTZ]2+ e pelos mesmos tratamentos térmicos acima mencionados. Na terceira série, os eletrocatalisadores foram preparados com três tipos de carbonos (Vulcan, Ketjenblack e Monarch), aos quais foi incorporado o complexo Fe[TPTZ]2+, seguido pelo tratamento térmico a 800 °C em atmosfera de nitrogênio e então por dopagem com amônia a 950 °C. As três séries de eletrocatalisadores sintetizados neste trabalho foram cuidadosamente caracterizadas por espectroscopia infra-vermelho e UV-Visível, difratometria de raio-x, microscopia eletrônica de transmissão, energia dispersiva de raios-x, espectroscipia Raman, espectroscopia fotoeletrônica de raios-x. As investigações eletroquímicas foram realizadas por voltametria cíclica (VC) e pelo levantamento de curvas de polarização de estado estacionário para a RRO, usando a técnica de eletrodo de disco/anel rotatório, com materiais catalíticos formando filmes finos depositados no eletrodo de disco. Nas três séries de catalisadores foram desenvolvidos materiais com bom desempenho para a RRO. Nos estudos da primeira série de catalisadores, notou-se que o material mais ativo foi aquele formado por WC-FeNx/C com 30 % de W/C e 5% de Fe pirolisado a 800 °C. Na segunda série foi observado que os desempenhos dos catalisadores variaram de acordo com o tipo de protocolo de nitretação, presença de ferro e temperatura de tratamento térmico. Em eletrólito alcalino, os eletrocatalisadores apresentaram maiores desempenhos, que resultaram bastante próximos em relação ao do catalisador de Pt dispersa em carbono usado como referência. Na terceira série de eletrocatalisadores investigados, verificou-se que o melhor desempenho obtido foi com o catalisador com carbono Monarch com amônia, cuja atividade catalítica resultou superior à dos demais, devido ao maior número de estruturas ativas FeNx e N/C formadas pelo tratamento com amônia. Os resultados nos meios ácido e alcalino para a primeira e segunda séries de eletrocatalisadores sugerem a ocorrência de um mecanismo indireto (2e- + 2e-), ou seja, em meio ácido (alcalino) primeiro o O2 reduz para H2O2 (HO2 ) e depois de H2O2 (HO2 ) para H2O. Os sítios predominantemente envolvidos na catálise da reação são WC e FeNx em meio ácido e WC e N/C em meio alcalino. Finalmente, para a terceira série de eletrocatalisadores o mecanismo reacional em meio ácido envolve um mecanismo direto de 4e-, com participação importante dos sítios ativos de Fe-N2. / This work aims to investigate low cost electrocatalysts based on tungsten carbide, carbon and iron submitted to different nitriding processes for the catalytic activity for the oxygen reduction reaction (ORR) in acid and alkaline electrolytes. The catalysts were divided into three distinct series, the first one comprising those with different tungsten carbide loads with respect to the carbon support, which were impregnated with the Fe2+ (2,4,6-Tris (2-pyridyl) - 1,3,5-triazine)2, [Fe (TPTZ)]2+, complex and treated at two different temperatures, 700 and 800 oC in nitrogen atmosphere. In the second series, the tungsten carbide load (30% W/C, m/m) was kept constant but this mixture was prepared using previously doped carbons using three different sources of nitrogen (HNO3, NH3 and HNO3/NH3); this was followed by the incorporation of the Fe[TPTZ]2+ complex and by the same heat treatments as mentioned above. In the third series, the electrocatalysts were prepared with three carbon types (Vulcan, Ketjenblack and Monarch), to which the Fe[TPTZ]2+ complex was added, followed by heat treatment at 800 °C under nitrogen and then by nitriding using a flow of ammonia at 950 °C. The three series of electrocatalysts synthesized in this work were carefully characterized by infra-red and UV-Visible spectroscopy, x-ray diffraction, transmission electron microscopy, x-ray energy dispersive, Raman spectroscopy, x-ray photoelectron spectroscopy. The electrochemical investigations were performed by cyclic voltammetry (CV) and by measurements of steady-state polarization curves for ORR using rotating ring-disc electrode technique, with catalytic materials forming thin films deposited on the disc. In the three catalyst series, materials with good performance for the ORR were developed. In the studies of the first series of catalysts, it was seen that the most active material was that formed by WC-FeNx/C with 30%W/C and 5% Fe pyrolyzed at 800 ° C. In the second series it was observed that the performances of the catalysts varied according to the type of nitriding protocol, presence of iron and temperature of heat treatment. The electrocatalysts showed higher performances in alkaline electrolyte, which were very close to that of a reference Pt/C catalyst. In the third series of electrocatalysts, the best performance was obtained with the Monarch carbon catalyst heat-treated with ammonia, whose catalytic activity was higher than all others, due to the greater number of FeNx and N/C active structures formed by the treatment with ammonia. The results in acidic and alkaline conditions for the first and second series of electrocatalysts suggest the occurrence of an indirect ORR mechanism (2e- + 2e-), that is, in acid (alkaline) media first O2 is reduced to H2O2 (HO2) followed by the reduction of H2O2 (HO2). The active sites predominantly involved in the reaction electrocatalysis are WC and FeNx in acid media and WC e N/C in alcaline media. Finally, for the third series of electrocatalysts, the acidic reaction involves a direct 4e- mechanism, having important participation of the Fe-N2 active sites.