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Synthesis and characterization of NiMo for efficient hydrogen production from water electrolysis
Full text linkNiMo-legeringer anses som svært aktive katalysatorer for Hydrogen Evolution Reaction (HER) i alkaliske elektrolytter. I denne studien blir den grunnleggende aktiviteten for HER av NiMo-legeringskatoder med sammenlignbare overflatearealer i alkalisk elektrolytt studert i detalj. To metoder for substratpreparering - den kjemiske etsingen med varierende tidsintervaller og den mekaniske poleringen utført av slipepapir i forskjellige størrelser på Ti-folier - har blitt brukt for å sammenligne deres effekt på den elektrokatalytiske ytelsen til materialet som studeres (NiMo-legeringskatoder) og identifisere den beste typen forbehandling som resulterer i dannelsen av den beste elektrokatalysatoren. Elektrodeponering av NiMo-legering ved -20 mA cm-2 og 15 minutter fra badløsningen inneholdende 79 g NiSO4 · 6H2O, 88 g Na3C6H5O7· 2H2O, og 44 g Na2MoO4 med den justerte pH til 10,5 med ammoniakkløsning ble påført for syntese av materialet under studien. Den elektrokatalytiske karakteriseringen av de syntetiserte NiMo-legeringene ble utført i 1 M KOH (pH = 14,7) media ved Linear Sweep Voltammetry (LSV) i et potensielt vindu på -1,35 til -0,90 V vs Hg/HgO og elektrokjemisk impedansspektroskopi (EIS) kl. – 1 mA cm-2, – 10 mA cm-2 og – 1 V. Studiet av morfologi, sammensetning og struktur ble utført ved hjelp av skanningselektronmikroskopi (SEM), Energy Dispersive X-Ray Spectroscopy (EDS) og X -Strålediffraksjon (XRD). Den beste forbehandlingsmetoden viste seg å være den mekaniske poleringen, og derfor viste gruppen av NiMo-prøver med denne substratforbehandlingsmetoden den laveste Tafel-hellingen (80,7 mV des-1), den høyeste utvekslingsstrømtettheten ( - 2,45 mA cm-2), Volmer-Herovsky-mekanisme med Volmer-trinn som ratebestemmende trinn (RDS) for HER, sammensetningen av Ni(63,9 at%), Mo (16,3 at%) og O (19,8 at%), atomforholdet Ni:Mo som 3,9:1, fine agglomererte partikler som danner homogen dekning på Ti-substratet, og den laveste avsetningen sjonspotensial. Alle prøvene viste en intensitetstopp som tilsvarer ansiktssentrert kubisk NiMo(111) og resten av diffraksjonstoppene ble fullstendig matchet med diffraksjonsmønsteret til sekskantet Ti. Den mest effektive HER-kinetikken ble observert i NiMo avsatt på 4 s etset Ti-substratgruppe ved EIS-karakterisering ved -10 mA cm-2, med Rct på 6,61 Ω. Det ble også observert at den elektrokatalytiske ytelsen øker med økningen av etsetiden. Alle disse resultatene påpekte at substratbehandling kan ha en betydelig effekt på den generelle ytelsen til NiMo på Ti-substratelektroden. Ytterligere arbeid kan gjøres ved å bruke andre forbehandlingsmetoder som ultralydrensing og varmegløding, og ved å bruke flere undersøkelsesteknikker som røntgenfotoelektronspektroskopi (XPS), kronoamperometri (CA), og for å samle inn mer allsidige data om elektrokatalytisk ytelsen til NiMo for HER i alkaliske medier.NiMo alloys are considered as highly active catalysts for the Hydrogen Evolution Reaction (HER) in alkaline electrolytes. In this study, the fundamental activity for the HER of NiMo alloy cathodes with comparable surface areas in alkaline electrolyte are studied in detail. Two methods for substrate preparation – the chemical etching with varying time intervals and the mechanical polishing conducted by different-size grinding papers on Ti-foils – have been employed to compare their effect on the electrocatalytic performance of the material under study (NiMo alloy cathodes) and identify the best type of pre-treatment that results in the formation of the best electrocatalyst. The electrodeposition of NiMo alloy at -20 mA cm-2 and 15 min from the bath solution containing 79 g of NiSO4 · 6H2O, 88 g of Na3C6H5O7· 2H2O, and 44 g of Na2MoO4 with the adjusted pH to 10.5 by ammonia solution was applied for the synthesis of the material under the study. The electrocatalytic characterization of the synthesized NiMo alloys was performed in 1 M KOH (pH = 14.7) media by Linear Sweep Voltammetry (LSV) in a potential window of -1.35 to -0.90 V vs Hg/HgO and Electrochemical Impedance Spectroscopy (EIS) at – 1 mA cm-2, – 10 mA cm-2, and – 1 V. The study of morphology, composition, and structure was conducted by Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS), and X-Ray Diffraction (XRD).The best pretreatment method was proved to be the mechanical polishing, and hence the group of NiMo samples with this substrate pretreatment method showed the lowest Tafel slope (80.7 mV dec-1), the highest exchange current density (- 2.45 mA cm-2), Volmer-Herovsky mechanism with Volmer step as Rate Determining Step (RDS) for HER, the composition of Ni(63.9 at%), Mo (16.3 at%), and O (19.8 at%), the atomic ratio of Ni:Mo as 3.9:1, fine agglomerated particles that form homogeneous coverage on the Ti substrate, and the lowest deposition potential. All samples demonstrated an intensity peak that corresponds to face-centered cubic NiMo(111) and the rest of the diffraction peaks were completely matched with the diffraction pattern of hexagonal Ti. The most effective HER kinetics was observed in the NiMo deposited on 4 s etched Ti substrate group by EIS characterization at -10 mA cm-2, with Rct of 6.61 Ω. Also, it was observed that the electrocatalytic performance increases with the increase of etching time. All these results pointed out that substrate treatment can have a significant effect on the overall performance of the NiMo on Ti substrate electrode. Further work may be done by an application of other pretreatment methods such as ultrasonic cleaning and heat annealing, and by applying more investigation techniques such as X-Ray Photoelectron Spectroscopy (XPS), Chronoamperometry (CA), and to collect more versatile data about electrocatalytic performance of NiMo for HER in alkaline media
Synthesis and characterization of NiMo for efficient hydrogen production from water electrolysis
No full textNiMo-legeringer anses som svært aktive katalysatorer for Hydrogen Evolution Reaction (HER) i alkaliske elektrolytter. I denne studien blir den grunnleggende aktiviteten for HER av NiMo-legeringskatoder med sammenlignbare overflatearealer i alkalisk elektrolytt studert i detalj. To metoder for substratpreparering - den kjemiske etsingen med varierende tidsintervaller og den mekaniske poleringen utført av slipepapir i forskjellige størrelser på Ti-folier - har blitt brukt for å sammenligne deres effekt på den elektrokatalytiske ytelsen til materialet som studeres (NiMo-legeringskatoder) og identifisere den beste typen forbehandling som resulterer i dannelsen av den beste elektrokatalysatoren. Elektrodeponering av NiMo-legering ved -20 mA cm-2 og 15 minutter fra badløsningen inneholdende 79 g NiSO4 · 6H2O, 88 g Na3C6H5O7· 2H2O, og 44 g Na2MoO4 med den justerte pH til 10,5 med ammoniakkløsning ble påført for syntese av materialet under studien. Den elektrokatalytiske karakteriseringen av de syntetiserte NiMo-legeringene ble utført i 1 M KOH (pH = 14,7) media ved Linear Sweep Voltammetry (LSV) i et potensielt vindu på -1,35 til -0,90 V vs Hg/HgO og elektrokjemisk impedansspektroskopi (EIS) kl. – 1 mA cm-2, – 10 mA cm-2 og – 1 V. Studiet av morfologi, sammensetning og struktur ble utført ved hjelp av skanningselektronmikroskopi (SEM), Energy Dispersive X-Ray Spectroscopy (EDS) og X -Strålediffraksjon (XRD). Den beste forbehandlingsmetoden viste seg å være den mekaniske poleringen, og derfor viste gruppen av NiMo-prøver med denne substratforbehandlingsmetoden den laveste Tafel-hellingen (80,7 mV des-1), den høyeste utvekslingsstrømtettheten ( - 2,45 mA cm-2), Volmer-Herovsky-mekanisme med Volmer-trinn som ratebestemmende trinn (RDS) for HER, sammensetningen av Ni(63,9 at%), Mo (16,3 at%) og O (19,8 at%), atomforholdet Ni:Mo som 3,9:1, fine agglomererte partikler som danner homogen dekning på Ti-substratet, og den laveste avsetningen sjonspotensial. Alle prøvene viste en intensitetstopp som tilsvarer ansiktssentrert kubisk NiMo(111) og resten av diffraksjonstoppene ble fullstendig matchet med diffraksjonsmønsteret til sekskantet Ti. Den mest effektive HER-kinetikken ble observert i NiMo avsatt på 4 s etset Ti-substratgruppe ved EIS-karakterisering ved -10 mA cm-2, med Rct på 6,61 Ω. Det ble også observert at den elektrokatalytiske ytelsen øker med økningen av etsetiden. Alle disse resultatene påpekte at substratbehandling kan ha en betydelig effekt på den generelle ytelsen til NiMo på Ti-substratelektroden. Ytterligere arbeid kan gjøres ved å bruke andre forbehandlingsmetoder som ultralydrensing og varmegløding, og ved å bruke flere undersøkelsesteknikker som røntgenfotoelektronspektroskopi (XPS), kronoamperometri (CA), og for å samle inn mer allsidige data om elektrokatalytisk ytelsen til NiMo for HER i alkaliske medier
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
Hydrogen production using the photoelectrochemical-photosynthetic methods
No full textThe scope of the PhD thesis is the development of a new method for simultaneous hydrogen production and organic pollutants’ reduction. For the purposes of this project, a novel photoelectrocatalytic-enzymatic hybrid system is presented for the first time, which is able to produce hydrogen under the simultaneous destruction of toxic and detrimental pollutants present in wastewaters. The main aim of the project is to replace the complex natural photosynthetic systems, such as PSII, PSI, FDX etc., with a semiconducting anode, which under illumination it will be able to oxidize organic pollutants, simultaneously. In addition, this system utilizes the cells of the green photosynthetic algae Chlamydomonas Reinhardtii, strain CC-124, which induce the hydrogenase enzymes and not purified hydrogenase enzymes, for the reduction of the H⁺ to H₂. It consists of a 2 compartments photoelectrochemical cell, where in the anodic compartment, the activation of a TiO₂ electrode by appropriate light is able to degrade most of the organic pollutants present in wastewaters. In the cathodic compartment and under anaerobic conditions, the green photosynthetic algae induce the hydrogenase enzymes, which have the ability to reduce hydrogen cations and forms molecular hydrogen. More specific, the destruction of the antibiotic Chloramphenicol, which acts as a model pollutant, will take place in the anodic compartment, while the photogenerated electrons in the TiO₂ anode are transferred to the cathode, where the hydrogenase enzymes catalyze the reduction of the H⁺ species to H₂. Parameters like the growing medium, detergent, electron relay and algae concentration have been optimized. Fifty percent reduction in the organic carbon content and almost complete destruction of the Chloramphenicol molecule is possible at the anode under photoelectrocatalytic conditions (light intensity 3.9 mW cm⁻²). At the same time, in the cathode compartment and in the presence of the algae culture Chlamydomonas Reinhardtii, 110 μmol H₂ are produced over a reaction time of 450 min, using 0.4 mM Triton X 100 for the cell membranes rapture and 0.01 mM Methyl Viologen (MV⁺²), which acts as an electron relay, in a Tris-Acetate-Phosphate (TAP) sulphur free medium. The enzymatic hydrogen production rate is equal to 0.24 μmol H₂ min⁻¹, while the yield of the system defined as IPCH2E is 1.56%. This hybrid system, which represents a method of artificial photosynthesis, has the potential to lead to an innovative and effective operational system under solar light for hydrogen production and wastewater treatment, simultaneously. The understanding and the mimic of Nature’s mechanisms are the “keys” for the development of environmentally friendly methods that will contribute to a viable and sustainable future for the planet.Ο σκοπός της Διδακτορικής Διατριβής είναι η παραγωγή υδρογόνου, ως καύσιμο νέας γενιάς, ταυτόχρονα με την αποικοδόμηση ρύπων που βρίσκονται σε υγρά απόβλητα. Για την εκπλήρωση του στόχου αυτού αναπτύχτηκε μια νέα μεθοδολογία, η οποία συνδυάζει την ενζυματική παραγωγή υδρογόνου με τη φωτοηλεκτροχημική διάσπαση οργανικών ρύπων. Για την υλοποίηση της μεθόδου κατασκευάστηκε και παρουσιάστηκε, για πρώτη φορά στη βιβλιογραφία ένα υβριδικό φωτοηλεκτροχημικό-ενζυματικό σύστημα, στο οποίο, ταυτόχρονα με την παραγωγή υδρογόνου στο καθοδικό του τμήμα από τα ένζυμα υδρογενάσης, στο ανοδικό τμήμα λαμβάνει χώρα η φωτοηλεκτροκαταλυτική οξείδωση οργανικών ρύπων. Ο κύριος στόχος της εργασίας ήταν η αντικατάσταση των πολύπλοκων φυσικών συστημάτων (PSII, PSI, FDX κ.α.) που λειτουργούν κατά τη φωτοσύνθεση με μια ημιαγώγιμη άνοδο, η οποία επιπλέον, υπό την επίδραση ακτινοβολίας, μπορεί ταυτόχρονα και να οξειδώνει οργανικές ενώσεις. Επίσης, καινοτομία αποτελεί το γεγονός πως στο καθοδικό τμήμα δε χρησιμοποιήθηκαν καθαρά ένζυμα, αλλά ολόκληρα τα ευκαριωτικά κύτταρα Chlamydomonas Reinhardtii το στέλεχος CC-124, τα οποία μπορούν και εκφράζουν τα ένζυμα υδρογενάσης σε συνθήκες έλλειψης θείου και οξυγόνου. Tα σημαντικότερα αποτελέσματα που προέκυψαν από την εφαρμογή της μεθόδου στην πρότυπη φωτοηλεκτροχημική-ενζυμική υβριδική κυψέλη συνοψίζονται ως εξής: Η οξείδωση και η ανοργανοποίηση 10 mg L⁻¹ αντιβιοτικού Χλωραμφενικόλη, το οποίο χρησιμοποιήθηκε ως ρύπος μοντέλο, ήταν 100% και 50%, αντίστοιχα, ύστερα από 8 ώρες φωτισμού (ένταση φωτός 3.9 mW cm⁻²) της ανόδου TiO₂, σε δυναμικό πόλωσης +0.6 V vs Ag/AgCl και πυκνότητα φωτορεύματος περίπου 28 μA cm⁻². Την ίδια στιγμή, στο καθοδικό τμήμα της κυψέλης παράχθηκαν σε θρεπτικό υλικό TAP-SF, παρουσία ~1.9 107 κυττάρων άλγεων mL⁻¹ (δραστικότητα ενζύμων υδρογενάσης ~1.75 10⁻² units), 0.4 mM Triton X 100 και 0.010 mM MV⁺², περίπου 110 μmol H₂ σε 7.5 ώρες φωτισμού της ανόδου, δηλαδή ρυθμός ενζυμικής παραγωγής υδρογόνου ίσος με 0.24 μmol H₂ min⁻¹. Η απόδοση του συστήματος που ορίζεται ως ο αριθμός των φωτονίων που προσπίπτει στην επιφάνεια της ανόδου και μετατρέπονται εμμέσως σε υδρογόνο ορίζεται ως IPCH2E και βρέθηκε ίσος με 1.56%. Ο ρόλος του απορρυπαντικού Triton X 100 είναι η διαλυτοποίηση των μεμβρανών των κυττάρων, ενώ το Methyl Viologen (MV⁺²) έχει το ρόλο του διαμεσολαβητή φορτίου από το ηλεκτρόδιο της καθόδου (ράβδος γραφίτη) στα ένζυμα υδρογενάσης. Πρόκειται για μια μέθοδο τεχνητής φωτοσύνθεσης, η οποία έχει τη δυνατότητα μακροπρόθεσμα να αξιοποιήσει την ηλιακή ακτινοβολία για την αντιμετώπιση της περιβαλλοντικής ρύπανσης, με ταυτόχρονη παραγωγή ενός καθαρού καυσίμου, όπως είναι το υδρογόνο. Η κατανόηση και η αντιγραφή των φυσικών συστημάτων, τα οποία η φύση έχει αναπτύξει εδώ και δισεκατομμύρια χρόνια, αποτελούν το «κλειδί» για την ανάπτυξη μεθόδων φιλικών και σε αρμονία με το φυσικό περιβάλλον, πράγμα που θα συμβάλλει σε μια βιώσιμη οικονομική και κοινωνική εξέλιξη της ανθρωπότητας
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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