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Hapniku redutseerumine raud ja koobalt ftalotsüaniiniga modifitseeritud šungiidil põhinevatel katalüsaatormaterjalidel
Get PDFElectrocatalytic oxygen reduction reaction (ORR) activity was studied on natural shungite-based materials prepared by functionalisation with Fe- and Co-phthalocyanine (Pc) com-plexes via pyrolysis. Structural and elemental composition of the pristine and modified cat-alysts were studied using several physical characterisation methods. The ORR activity of the materials was assessed by the rotating disc electrode method in alkaline and acidic media, resulting in superior ORR performance of KOH-treated FePc modified shungite material in 0.1 M KOH solution. Stability testing performed on most active catalysts in alkaline media showed a high stability of the prepared shungite-based electrocatalysts. The testing in 0.5 M H2SO4 solution also revealed the superior ORR activity of KOH-treated FePc modified shungite material.
In estonian: Käesolevas töös uuriti hapniku redutseerumist katalüsaatormaterjalidel, mis põhinesid püro-lüüsi teel valmistatud Fe- ja Co-ftalotsüaniiniga (Pc) modifitseeritud šungiidil. Valmistatud materjalide omadusi uuriti mitmete füüsikaliste karakteriseerimismeetoditega. Hapniku elektrokeemilist redutseerumist valmistatud materjalidel uuriti nii aluselises kui ka happeli-ses lahuses. Kõige aktiivsem hapniku redutseerumise katalüsaator aluselise keskkonna jaoks valmistati KOH lahuses töödeldud šungiidist, mis oli modifitseeritud FePc ühendiga. Sta-biilsustestid 0,1 M KOH lahuses näitasid valmistatud katalüsaatormaterjalide head stabiil-sust. Happelises keskkonnas tehtud eksperimendid näitasid samuti kõige paremat aktiivsust hapniku redutseerumiseks KOH lahuses töödeldud ja FePc ühendiga valmistatud materjalil
Hapniku redutseerimine paksude antrakinooni kiledega ja metüülantrakinooniga modifitseeritud klaassüsinikelektroodidel
Get PDFArüülkilede ja nanokomposiitmaterjalidega modifitseeritud süsinik- ja metallelektroodide pinna ja elektrokeemiliste omaduste karakteriseerimine
Get PDFVäitekirja elektrooniline versioon ei sisalda publikatsiooneKäesoleva doktoritöö eesmärk oli valmistada ja uurida arüülkiledega modifitseeritud süsinik- ja metallelektroodide ning mitteväärismetallidel põhinevate katalüsaatormaterjalide pinna- ja elektrokeemilisi omadusi. Valmistatud elektroodide pinda iseloomustati erinevate füüsikaliste ja elektrokeemiliste meetoditega (röntgenfotoelektronspektroskoopia (XPS), aatomjõumikroskoopia (AFM), tsükliline voltamperomeetria ja pöörleva ketaselektroodi meetod (RDE)). Doktoritöö esimene ja teine osa kirjeldavad süsinik- ja metallelektroodide spontaanset ja ka elektrokeemilist modifitseerimist 9,10-antrakinooni (AQ) ja 4-nitrofenüülrühmadega (NP) diasooniumisoolade redutseerumise meetodil. Elektrokeemiliseks modifitseerimiseks kasutati nii „tavalist“, redokspookimise kui ka esmakordselt redokspookimise ja RDE kombineeritud meetodit. XPS ja AFM analüüsil tehti kindlaks arüülrühmade olemasolu elektroodidel ning lisaks uuriti nende mõju hapniku redutseerumisreaktsioonile ja elektroodi pinna blokeerumist arüülkile tõttu Fe(CN)63/4 redokspaari suhtes. Tehti kindlaks, et paksemate ja suurema elektroaktiivsete arüülrühmade hulgaga kilede valmistamiseks oli kõige sobivam redokspookimise ja RDE kombineeritud meetod. Antud meetodit kasutades valmistati suurima teadaoleva elektroaktiivsete AQ rühmade pindkontsentratsiooniga modifitseeritud klaassüsinik, Au ja Cu elektroodid ning samuti kõige paksem arüülkile käesolevas doktoritöös (47 nm), mis saadi NP kilega Cu elektroodi korral. Doktoritöö viimases osas uuriti elektrokedratud polümeeridel põhinevaid süsiniknanotorudega komposiitmaterjale ja ränioksükarbiidil põhinevaid materjale eesmärgiga kasutada neid mitteväärismetallkatalüsaatoritena hapniku redutseerumisreaktsioonil. Kõige aktiivsem katalüsaatormaterjal saadi ränioksükarbiidil põhinevate materjalide puhul, mis sisaldas siirdemetalli (Co) ja lämmastikku. Sellel katalüsaatoril toimus hapniku redutseerumine 4-elektronilise protsessina, mis on oluline kütuseelemendis rakendamise seisukohalt. Antud katalüsaatormaterjali hapniku redutseerumise aktiivsuse olulisimaks põhjuseks leiti olevat materjali struktuuri pürolüüsi käigus viidud aktiivsed lämmastikurühmad ja siirdemetallThe aim of the present PhD thesis was to prepare and characterise the aryl film modified carbon and metal electrodes and in addition, the nonprecious metal (NPM) catalysts. The surface of the prepared electrodes was investigated by several physical and electrochemical methods (e.g. X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), cyclic voltammetry and the rotating disc electrode (RDE) method). The first and the second part of the PhD thesis describe the spontaneous and electrochemical modification of carbon and metal electrodes with 9,10-anthraquinone (AQ) and 4-nitrophenyl (NP) groups using the aryldiazonium salt reduction method. For the electrochemical functionalisation, the “normal” electrografting, redox grafting (RG) and the RG and RDE combined methods were used. The presence of the aryl groups on the electrodes was ascertained by the XPS and AFM experiments. Additionally, the influence of the aryl film on the oxygen reduction reaction (ORR) activity and towards the Fe(CN)63/4 redox probe was studied. It was found that for the preparation of thicker films with higher amount of electroactive aryl groups, the RG and RDE combined method was beneficial. Via latter method, the highest known amount of electroactive AQ groups was obtained in the aryl films on glassy carbon, Au and Cu electrodes and also, the thickest film of 47 nm was prepared by this method in case of NP film modified Cu electrode. In the last part of the PhD thesis, the ORR was studied on polymer based carbon nanotube containing composites and on the siliconoxycarbide based materials for the application as NPM catalysts. The highest ORR activity was obtained in case of transition metal (Co) and nitrogen containing siliconoxycarbide material. On the latter catalyst material the ORR proceeds via 4-electron pathway that is crucial for the fuel cell applications. The high ORR performance of the latter catalyst was attributed to the introduction of N-functionalities and transition metal into the material during the pyrolysis.https://www.ester.ee/record=b524279
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Cobalt, iron, and nitrogen co-doped graphene coated ceramic nanowire-based bifunctional oxygen electrocatalyst for Zn-air battery
No full textStructural and elemental composition of several graphene-coated Al2O3 nanowire-based cat-
alyst materials prepared by functionalization with dicyandiamide and Fe and Co salts via
pyrolysis were studied using several physical characterisation methods. Electrocatalytic ox-
ygen reduction reaction (ORR) activity of the materials was studied using the rotating disk
electrode method in a 0.1 M KOH solution. Using the same method, the oxygen evolution
reaction activity was studied for the catalyst material with the highest ORR activity. Addi-
tionally, the catalyst’s rechargeable Zn-air battery performance was assessed, showing su-
perior power output and cycle life than those of a commercial Pt-Ru/C catalyst
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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