Metal-organic frameworks (MOFs) have attracted increasing interest for broad applications in catalysis and gas separation due to their high porosity. However, the insulating feature and the limited active sites hindered MOFs as photocathode active materials for application in photoelectrocatalytic hydrogen generation. Herein, we develop a layered conductive two-dimensional conjugated MOF (2D c-MOF) comprising sp-carbon active sites based on arylene-ethynylene macrocycle ligand via CuO4 linking, named as Cu3HHAE2. This sp-carbon 2D c-MOF displays apparent semiconducting behavior and broad light absorption till the near-infrared band (1600 nm). Due to the abundant acetylene units, the Cu3HHAE2 could act as the first case of MOF photocathode for photoelectrochemical (PEC) hydrogen generation and presents a record hydrogen-evolution photocurrent density of ≈260 μA cm−2 at 0 V vs. reversible hydrogen electrode among the structurally-defined cocatalyst-free organic photocathodes.

Metallorganische Gerüstverbindungen (englisch metal–organic frameworks, MOFs) sind aufgrund ihrer hohen Porosität von großem Interesse für eine Vielzahl von Anwendungen in der Katalyse und Gastrennung. Eine begrenzte Anzahl an aktiven Zentren sowie das Verhalten als elektrischer Isolator machen den Einsatz von MOFs als aktives Photokathodenmaterial für die photoelektrokatalytische Wasserstoffproduktion allerdings nicht möglich. Wir berichten hiermit von der Entwicklung eines gestapelten, leitfähigen, zweidimensional-konjugierten MOFs (englisch 2D conjugated MOF, 2D c-MOF) welches aktive sp-Kohlenstoffzentren enthält. Der MOF Cu3HHAE2 basiert auf einem makrozyklischen Aryl-Alkin Liganden, welcher via CuO4 Einheiten verknüpft ist. Dieser sp-Kohlenstoff haltige 2D c-MOF zeigt Halbleitereigenschaften und eine breite Absorption bis in den nah-infraroten Bereich (1600 nm). Erstmalig kann dank der hohen Anzahl an Dreifachbindungen Cu3HHAE2 als MOF-Photokathode für die photoelektrochemische (PEC) Wasserstoffentwicklung verwendet werden. Verglichen mit anderen strukturell definierten, co-Katalysator freien organischen Photokathoden, zeigt er eine Rekordphotostromdichte für die Wasserstoffentwicklung von ≈ 260 μAcm⁻ ² bei 0 V gegen die reversible Wasserstoffelektrode (englisch reversible hydrogen electrode RHE).

Os azo corantes atualmente são considerados um assunto preocupante no que se refere à saúde pública e ambiental, pois quando lançados nos efluentes industriais contaminam o meio ambiente. Infelizmente, o método convencional de tratamento de efluentes têxteis, bem como de águas brutas que os recebem não são capazes de remover de maneira eficaz os corantes bem como sua toxicidade. Dentro deste contexto, este trabalho teve como objetivo avaliar a eficiência do tratamento de amostras aquosas por fotoeletrocatálise em comparação com a cloração convencional como método alternativo de degradação de azo corantes, usando os corantes Disperse Orange 1, Disperse Red 1 e Disperse Red 13 como modelo. Adicionalmente, foi avaliada a citotoxicidade dos corantes originais em condrócitos bovinos e células HepG2 em cultura em monocamadas e 3D. Para tanto, soluções desses corantes originais, clorados e fotoeletrocatalisados foram avaliadas utilizando ensaios de genotoxicidade/mutagenicidade, citotoxicidade e ecotoxicidade. Todos os corantes originais e clorados foram genotóxicos para as células HepG2 no ensaio cometa. Para o ensaio com Salmonella, a cloração reduziu a mutagenicidade dos corantes para a linhagem YG1041 e aumentou o efeito para a linhagem TA98, exceto o Disperse Red 13 que teve a mutagenicidade reduzida para as duas linhagens após cloração. A fotoeletrocatálise removeu tanto a genotoxicidade quanto a mutagenicidade. Somente o Disperse Orange 1 induziu apoptose pelo ensaio com anexina V, mas essa citotoxicidade foi removida após os tratamentos. Os corantes Disperse Red 1 e Disperse Red 13 foram tóxicos para D. similis enquanto somente o Disperse Red 1 foi tóxico para V. fischeri, sendo que os tratamentos por cloração e fotoeletrocatálise diminuíram a toxicidade apresentada. Os corantes Disperse Orange 1 e Disperse Red 13 passaram a ser tóxicos para V. fischeri após cloração, sendo que a fotoeletrocatálise do Disperse Red 13 também gerou produtos tóxicos para esse organismo. Assim, embora seja um método de tratamento promissor, atenção deve ser dada na avaliação e aplicação da fotoeletrocatálise como um método alternativo à cloração. Os corantes originais Disperse Orange 1 e Disperse Red 13 diminuíram a atividade mitocondrial dos condrócitos, sendo que o Disperse Red 13 também diminuiu a produção de lactato. Todos os corantes reduziram a atividade mitocondrial das células HepG2 em monocamadas, ao passo que o Disperse Orange 1 deixou de exercer esse efeito no cultivo em 3D. Somente o Disperse Red 13 diminuiu a atividade de desidrogenases das células HepG2 e tal efeito foi observado tanto no cultivo em monocamadas quanto em 3D. / The azo dyes are currently considered as a concern regarding the environmental and public health, since when released in industrial effluents they pollute the environment. Unfortunately, the conventional method of treatment of textile effluents is not able to effectively remove both dyes and their toxicity. Within this context, this study aimed to evaluate the effectiveness of the treatment of aqueous samples by photoelectrocatalysis compared to conventional chlorination as an alternative method of degradation of azo dyes, using the dyes Disperse Orange 1, Disperse Red 1 and Disperse Red 13 as a model. Additionally, we evaluated the cytotoxicity of the original dyes using HepG2 cells and chondrocytes cultured in monolayer and in 3D. To this end, solutions of these original dyes, chlorinated and photoelectrocatalysed were evaluated using tests of genotoxicity / mutagenicity, cytotoxicity and ecotoxicity. All the dyes, original and chlorinated, were genotoxic to HepG2 cells in the comet assay. For the test with Salmonella, chlorination reduced the mutagenicity of the dyes for the YG1041 strain and increased the effect for the TA98 strain, except Disperse Red 13, which had the mutagenic effect reduced for both strains after chlorination. The photoelectrocatalysis removed both genotoxicity and mutagenicity. Only Disperse Orange 1 induced apoptosis by annexin V assay, but this cytotoxicity was removed after treatment. The dye Disperse Red 1 and Disperse Red 13 were toxic to D. similis while only the Disperse Red 1 was toxic to V. fischeri, and the treatment by chlorination and photoelectrocatalysis decreased the toxicity showed. The dyes Disperse Orange 1 and Disperse Red 13 began toxic to V. fischeri after chlorination, and the photoelectrocatalysis of the Disperse Red 13 generated toxic products for this organism. So, while it is a promising treatment method, attention should be given in the evaluation and application of photoelectrocatalysis as an alternative to chlorination. The dyes Disperse Orange 1 and Disperse Red 13 decreased the mitochondrial activity of chondrocytes, and the dye Disperse Red 13 also decreased the production of lactate. All the dyes reduced the mitochondrial activity of the HepG2 cells cultured in monolayer, while the Disperse Orange 1 did no show this effect in 3D. Only Disperse Red 13 decreased the activity of dehydrogenases of HepG2 cells and this effect was observed both in monolayer and in 3D.

H ιδέα της παρούσας μεταπτυχιακής ερευνητικής εργασίας βασίζεται στην παραγωγή ηλεκτρικής ενέργειας με φωτοαποικοδόμηση οργανικών ρύπων, μέσω φωτοηλεκτροχημικών κυψελίδων(PECs). Mε τον τρόπο αυτό επιτυγχάνεται η κατανάλωση των οργανικών ουσιών και η μετατροπή της ηλιακής ακτινοβολίας σε ηλεκτρική ενέργεια. Ο σκοπός της εργασίας ήταν η παρασκευή, ο χαρακτηρισμός, η μελέτη φωτοευαίσθητων ηλεκτροκαταλυτών και η μορφοποίηση τους σε ηλεκτρόδια, των οποίων εξετάστηκε και αναλύθηκε η φωτοηλεκτροχημική τους συμπεριφορά. Η φωτοηλεκτροχημική κυψελίδα αποτελείται από τα ηλεκτρόδια ανόδου και καθόδου, τα οποία φέρουν το φωτοκαταλύτη και τον ηλεκτροκαταλύτη αντίστοιχα. Εξαιτίας του n-τύπου ημιαγωγού που φέρει η φωτοάνοδος καθώς και της πρόσπτωσης της ηλεκτρομαγνητικής ακτινοβολίας πάνω στον ημιαγωγό, παρατηρείται η απορρόφηση φωτονίων και ο σχηματισμός ζεύγους ηλεκτρονίων-οπών. Η διαδικασία απορρόφησης ενός φωτονίου,για τη δημιουργία φωτοφορέων,απαιτεί το ποσό ενέργειας του φωτονίου να είναι μεγαλύτερο ή ίσο από/με το ενεργειακό χάσμα του ημιαγωγού. O ρυθμός επανασύνδεσης των φωτοπαραγόμενων ηλεκτρονίων και οπών περιορίζεται, με τη χρήση «θυσιαζόμενων ενώσεων», οι οποίες μπορεί να είναι δέκτες ή δότες ηλεκτρονίων. Με τον τρόπο αυτό προκαλούνται στην επιφάνεια του ημιαγωγού μη αντιστρεπτές αντιδράσεις, όπως οξείδωση των φωτοπαραγόμενων οπών, ώστε οι διαθέσιμοι φορείς φορτίου να ξεκινήσουν τις οξειδοαναγωγικές αντιδράσεις. Παράδειγμα, τέτοιων θυσιαστήριων ενώσεων αποτελεί η μεθανόλη, η οποία χρησιμοποιήθηκε στη συγκεκριμένη ερευνητική εργασία. Ως φωτοκαταλύτες χρησιμοποιήθηκαν η νανοκρυσταλλική τιτανία, TiO2 και ο σύνθετος ημιαγωγός TiO2/CdS, ο οποίος και παρασκευάστηκε με τη μέθοδο SILAR. Συγκεκριμένα το διοξείδιο του τιτανίου είναι η εμπορικά διαθέσιμη Degussa P-25, με αναλογία ανατάση:ρουτηλίου 3:1. Ως ηλεκτροκαταλύτης χρησιμοποιήθηκε ο εμπορικός καταλύτης Pt (30%)/C, πάνω σε αγώγιμο ύφασμα άνθρακα (Carbon Cloth). Η μελέτη των ηλεκτροδίων πραγματοποιήθηκε σε κατάλληλους φωτοηλεκτροχημικούς αντιδραστήρες, που σχεδιάστηκαν και κατασκευάστηκαν από τον κ. Λιανό για το σκοπό αυτό, ενώ έγινε χρήση λαπτήρα προσομοίωσης ορατής και υπεριώδους ακτινοβολίας. Η νανοκρυσταλλική τιτανία (ΤiO2) ως φωτοκαταλύτης, έχει ενεργειακό χάσμα 3,2eV και απορροφά φωτόνια μόνο στο υπεριώδες φάσμα της ηλεκτρομαγνητικής ακτινοβολίας. Για την αντιμετώπιση του ζητήματος αυτού, τοποθετήθηκε ευαισθητοποιητής θειούχου καδμίου (Csd) του οποίου το ενεργειακό χάσμα είναι 2,42eV και ενεργειακά έχει υψηλότερη στάθμη, από το διοξείδιο του τιτανίου, με αποτέλεσμα την αύξηση της απόκρισης στο ορατό φάσμα. Η ορατή ακτινοβολία απορροφάται από τον φωτοευαισθητοποιητή, ο οποίος διεγείρεται και εφόσον το ενεργειακό επίπεδο του διεγερμένου ηλεκτρονίου είναι ηλεκτραρνητικότερο από τη στάθμη αγωγιμότητας του TiO2, μεταπηδά στο TiO2 και συμμετέχει στην φωτοηλεκτροχημική διαδικασία. Η οπή που διαχωρίζεται από το διεγερμένο ηλεκτρόνιο, παραμένει στον φωτοευαισθητοποιητή και συμμετέχει σε αντιδράσεις οξείδωσης. Η ποιότητα και η αποτελεσματικότητα της καθόδου, παίζει εξίσου σπουδαίο ρόλο με εκείνη της ανόδου. Η απόδοση των φωτοηλεκτρικών κυψελίδων ελέγχεται μέσω του συντελεστή πληρότητας (Fill Factor), ο οποίος φαίνεται να παρουσιάζει μεγαλύτερη τιμή όσο αυξάνονται οι επιφάνειες των ηλεκτροδίων της ανόδου και της καθόδου, ενώ βέλτιστη απόδοση της φωτοηλεκτροχημικής κυψελίδας έχει επιτευχθεί με τη χρήση ηλεκτροδίου Carbon Cloth εμπλουτισμένου με νανοσωματίδια Pt (0.5mg Pt/cm2). Οι κυριότερες κατηγορίες των οργανικών ενώσεων που χρησιμοποιούνται ως οργανικοί ρύποι είναι οι αλκοόλες, οι πολυόλες και τα οξέα, ενώ στην παρούσα εργασία πιο αποδοτική φάνηκε να είναι η χρήση της μεθανόλης. / The idea behind this master’s degree thesis is based on the production of electrical energy through photo-degradation of organic emissions using photo-electrochemical cells. This way the consumption of the organic emissions and the conversion of the solar power to electricity are achieved. This thesis was aiming at the production, the characterization and the study of photosensitive electrocatalysts and turning them into electrodes, whose electrochemical behavior was studied and analyzed. The photo-electrochemical fuel cell is composed of the anode and cathode electrodes, who bare the photocatalyst and electrocatalyst respectively. Due to the n-type semiconductor on the photo-anode and its exposure to electromagnetic radiation, consumption of photons is observed and hole-electron pairs are formed. The energy of the incoming photon needs to be higher than the band gap of the semiconductor, for it to be absorbed and carriers to be created. The recombination rate of those carriers is reduced by using sacrificial agents or hole scavengers, which can be donors or acceptors of electrons. This way non- reversible reactions are achieved. Example of those is methanol, which was used in the present thesis. As photo-catalysts nanocrystals of titanium oxide and the composite semiconductor TiO2/CdS were used. The electro-catalyst Pt/C on carbon cloth was utilized. The study of the electrodes was performed used photo-electrochemical reactors designed by Prof. Lianos in combination with lamps simulating the solar spectrum. The nanocrystals of titanium oxide have a band gap of 3.2eV (in the UV region) which is the reason why CdS was deposited on top. The later has a band gap of 2.42eV and so increases the absorption in the visible region of the spectrum. The visible radiation is absorbed by the CdS layer and since the excited electron in more electronegative than the conduction band of the titanium oxide, it lowers its energy by hopping to the titanium oxide layer and participates in the photo-electrochemical procedure. The hole that’s left behind in the CdS layer is participating in the oxidation reactions. The performance of the photoelectrical cells was calculated through the fill factor and has an increasing value for increasing area of the electrodes. The optimum performance of the photoelectrochemical fuel cell was achieved by using a carbon cloth electrode enriched with Pt (0.5mg Pt/cm2). The primary categories of organic compounds used as organic emissions are alcohols, polyols and acids. The optimum performance was achieved by using methanol.

Το αντικείμενο της διδακτορικής διατριβής είναι η σύνθεση, ο χαρακτηρισμός και η μελέτη φωτοευαίσθητων ηλεκτροκαταλυτών TiO2 και η μορφοποίηση τους σε ηλεκτρόδια, τα οποία και μελετήθηκαν ως προς την φωτοηλεκτροχημική παραγωγή υδρογόνου από νερό ή/και οργανικές ενώσεις. Τα ηλεκτρόδια λεπτών υμενίων παρασκευάστηκαν με τη μέθοδο εμβάπτισης – επίστρωσης σε διάλυμα TiO2. Τα ηλεκτρόδια Τιτάνιας ήταν νανοπορώδη και παρουσίαζαν νανοκρυσταλλική δομή ανατάση με μέγεθος σωματιδίων 15 nm. Η μελέτη των ηλεκτροδίων πραγματοποιήθηκε σε φωτοηλεκτροχημικό αντιδραστήρα. Τα αποτελέσματα έδειξαν ότι η φωτοβόληση των ηλεκτροδίων τιτάνιας τα ενεργοποιεί, διεγείροντας ηλεκτρόνια στη ζώνη αγωγιμότητας και δημιουργώντας οπές στη ζώνη σθένους. Για την παραγωγή υδρογόνου ήταν απαραίτητη η επιβολή δυναμικού ή η παρουσία οργανικών ενώσεων στον ηλεκτρολύτη. Ο ρυθμός παραγωγής υδρογόνου βελτιστοποιήθηκε συναρτήσει του πάχους του υμενίου και της συγκέντρωσης των οργανικών ενώσεων στον ηλεκτρολύτη. Συμπερασματικά έχει τεράστιο δυναμικό για εφαρμογή σε φωτοηλεκτροχημικά κελιά καυσίμου για ταυτόχρονο καθαρισμό υδάτων από οργανικούς ρύπους και παραγωγή ενός «καθαρού» καυσίμου, του υδρογόνου. / The object of this thesis is the composition, characterization and the study of photosensitive TiO2 electrocatalysts and their formation in electrodes, which were studied for the photoelectrochemical production of hydrogen from water and/or organic compounds. The thin film electrodes were prepared with the dip - coating method in TiO2 solution. The titania electrodes were nanoporous and nanocrystaline, of anatase phase with particle size 15 nm. The study of electrodes took place in a photoelectrochemical reactor. The results showed that the illumination of the titania electrode activates it, arousing electrons in the conduction band and creating holes in the valence band. For the production of hydrogen, it was necessary to apply potential, or the presence of organic compounds in the electrolyte. The production rate of hydrogen was optimised with respect to the thickness of the film and the concentration of organic compounds in the electrolyte. In conclusion, this method has enormous potential for application in photoelectrochemical fuel cells for simultaneous cleaning of water from organic pollutants and production of “clean” fuel, hydrogen.

Ce travail de thèse traite de la production d’hydrogène par le procédé de photoélectrocatalyse en utilisant une photoanode à base de nanotubes de TiO2 verticalement alignés. L’utilisation du TiO2 étant limité pour des applications solaires en raison de son large gap, il est nécessaire de le modifier. Deux approches sont proposées pour modifier les nanotubes de TiO2 et leur permettre d’absorber la lumière visible. La première est une modification chimique du TiO2 par co-dopage cationique-anionique (Ta-N) ou (Nb-N). Les cations sont insérés durant la croissance des nanotubes grâce à une approche inédite, et l’azote est inséré durant le traitement thermique. Ceci a pour effet la formation d’orbitales hybrides qui entraîne une réduction du gap et une activité sous lumière visible, tout en permettant une stabilité de la structure. La seconde approche consiste à déposer des nanoparticules d’Ag sur la surface des nanotubes de TiO2. Grâce au contrôle de la morphologie des nanoparticules d’Ag, leur résonnance plasmonique permet de stimuler l’absorption du TiO2 et ainsi d’augmenter son rendement à la fois sous lumière UV et sous lumière visible. / This work is about the production of hydrogen by photoelectrocatalysis using a vertically aligned TiO2 nanotubes based photoanode. Utilization of TiO2 for solar applications is limited due to its large band gap, it has to be modified. Two approaches are proposed for the modification of the TiO2 nanotubes to make them absorb visible light. The first one is the chemical modification of the TiO2 by (Ta-N) or (Nb-N) cationic-anionic co-doping. Cations are inserted during the growth of the nanotubes by a novel approach, and nitrogen is inserted during heat treatment. This leads to the formation of hybrid orbitals resulting in a band gap reduction and of activity under visible light. The second approach consists of the deposition of Ag nanoparticles on the surface of the TiO2 nanotubes. Thanks to the control of the morphology of the Ag nanoparticles, their plasmonic resonance can enhance the absorption of TiO2 and thus increase its activity both under UV and visible light.

Os azo corantes atualmente são considerados um assunto preocupante no que se refere à saúde pública e ambiental, pois quando lançados nos efluentes industriais contaminam o meio ambiente. Infelizmente, o método convencional de tratamento de efluentes têxteis, bem como de águas brutas que os recebem não são capazes de remover de maneira eficaz os corantes bem como sua toxicidade. Dentro deste contexto, este trabalho teve como objetivo avaliar a eficiência do tratamento de amostras aquosas por fotoeletrocatálise em comparação com a cloração convencional como método alternativo de degradação de azo corantes, usando os corantes Disperse Orange 1, Disperse Red 1 e Disperse Red 13 como modelo. Adicionalmente, foi avaliada a citotoxicidade dos corantes originais em condrócitos bovinos e células HepG2 em cultura em monocamadas e 3D. Para tanto, soluções desses corantes originais, clorados e fotoeletrocatalisados foram avaliadas utilizando ensaios de genotoxicidade/mutagenicidade, citotoxicidade e ecotoxicidade. Todos os corantes originais e clorados foram genotóxicos para as células HepG2 no ensaio cometa. Para o ensaio com Salmonella, a cloração reduziu a mutagenicidade dos corantes para a linhagem YG1041 e aumentou o efeito para a linhagem TA98, exceto o Disperse Red 13 que teve a mutagenicidade reduzida para as duas linhagens após cloração. A fotoeletrocatálise removeu tanto a genotoxicidade quanto a mutagenicidade. Somente o Disperse Orange 1 induziu apoptose pelo ensaio com anexina V, mas essa citotoxicidade foi removida após os tratamentos. Os corantes Disperse Red 1 e Disperse Red 13 foram tóxicos para D. similis enquanto somente o Disperse Red 1 foi tóxico para V. fischeri, sendo que os tratamentos por cloração e fotoeletrocatálise diminuíram a toxicidade apresentada. Os corantes Disperse Orange 1 e Disperse Red 13 passaram a ser tóxicos para V. fischeri após cloração, sendo que a fotoeletrocatálise do Disperse Red 13 também gerou produtos tóxicos para esse organismo. Assim, embora seja um método de tratamento promissor, atenção deve ser dada na avaliação e aplicação da fotoeletrocatálise como um método alternativo à cloração. Os corantes originais Disperse Orange 1 e Disperse Red 13 diminuíram a atividade mitocondrial dos condrócitos, sendo que o Disperse Red 13 também diminuiu a produção de lactato. Todos os corantes reduziram a atividade mitocondrial das células HepG2 em monocamadas, ao passo que o Disperse Orange 1 deixou de exercer esse efeito no cultivo em 3D. Somente o Disperse Red 13 diminuiu a atividade de desidrogenases das células HepG2 e tal efeito foi observado tanto no cultivo em monocamadas quanto em 3D. / The azo dyes are currently considered as a concern regarding the environmental and public health, since when released in industrial effluents they pollute the environment. Unfortunately, the conventional method of treatment of textile effluents is not able to effectively remove both dyes and their toxicity. Within this context, this study aimed to evaluate the effectiveness of the treatment of aqueous samples by photoelectrocatalysis compared to conventional chlorination as an alternative method of degradation of azo dyes, using the dyes Disperse Orange 1, Disperse Red 1 and Disperse Red 13 as a model. Additionally, we evaluated the cytotoxicity of the original dyes using HepG2 cells and chondrocytes cultured in monolayer and in 3D. To this end, solutions of these original dyes, chlorinated and photoelectrocatalysed were evaluated using tests of genotoxicity / mutagenicity, cytotoxicity and ecotoxicity. All the dyes, original and chlorinated, were genotoxic to HepG2 cells in the comet assay. For the test with Salmonella, chlorination reduced the mutagenicity of the dyes for the YG1041 strain and increased the effect for the TA98 strain, except Disperse Red 13, which had the mutagenic effect reduced for both strains after chlorination. The photoelectrocatalysis removed both genotoxicity and mutagenicity. Only Disperse Orange 1 induced apoptosis by annexin V assay, but this cytotoxicity was removed after treatment. The dye Disperse Red 1 and Disperse Red 13 were toxic to D. similis while only the Disperse Red 1 was toxic to V. fischeri, and the treatment by chlorination and photoelectrocatalysis decreased the toxicity showed. The dyes Disperse Orange 1 and Disperse Red 13 began toxic to V. fischeri after chlorination, and the photoelectrocatalysis of the Disperse Red 13 generated toxic products for this organism. So, while it is a promising treatment method, attention should be given in the evaluation and application of photoelectrocatalysis as an alternative to chlorination. The dyes Disperse Orange 1 and Disperse Red 13 decreased the mitochondrial activity of chondrocytes, and the dye Disperse Red 13 also decreased the production of lactate. All the dyes reduced the mitochondrial activity of the HepG2 cells cultured in monolayer, while the Disperse Orange 1 did no show this effect in 3D. Only Disperse Red 13 decreased the activity of dehydrogenases of HepG2 cells and this effect was observed both in monolayer and in 3D.

This diploma thesis deals with the coating and printing of thin layers based on nanoparticles of titanium dioxide and organosilica binder on various substrates. The influence of the ratio of the both components on the activity of the prepared immobilized layers was studied. Five compositions with different ratios of TiO2 and binder were prepared. The work focuses mainly on the study of photocatalytic and photoelectrocatalytic properties of prepared layers. It was also important to characterize the mechanical properties of the layer such as hardness or adhesion. Both photocatalytic and photoelectrocatalytic activity were determined by monitoring the degradation of the model pollutants in aqueous solutions. The dye Acid Orange 7 and UV filter 2-hydroxy-4-methoxybenzophenone were used in conjunction with UV/VIS spectroscopy or high performance liquid chromatography techniques. Both photocatalytic and photoelectrocatalytic activity were expressed using kinetic characteristics.

[ES] La presente Tesis Doctoral se centra en la síntesis de nanoestructuras híbridas de TiO2/ZnO para su utilización como fotoelectrocatalizadores durante la producción de hidrógeno a partir de la rotura de la molécula de agua mediante fotoelectrocatálisis y la degradación fotoelectrocatalítica de pesticidas. La principal ventaja de las nanoestructuras híbridas de TiO2/ZnO frente a otros fotocatalizadores basados en materiales semiconductores radica en su capacidad para formar heterouniones en las que se intercalan las bandas de valencia y conducción de ambos semiconductores. Este fenómeno produce una disminución del ancho de banda del fotoelectrocatalizador y de los procesos de recombinación de los pares electrón-hueco fotogenerados y un aumento del rango de absorción de la luz, lo que mejora sus propiedades como fotoelectrocatalizadores. Las nanoestructuras híbridas de TiO2/ZnO obtenidas en la presente Tesis Doctoral se sintetizaron mediante electrodeposición de ZnO sobre nanoesponjas de TiO2. Las nanoesponjas de TiO2 se formaron mediante anodizado electroquímico de titanio en condiciones hidrodinámicas y, posteriormente, se electrodepositó ZnO sobre la superficie de las nanoesponjas de TiO2 modificando la concentración de precursor (Zn(NO3)2 0.5-60 mM), la temperatura (25-75 °C) y el tiempo (15-60 min). Además, se estudió la influencia de electrodepositar ZnO sobre nanoesponjas de TiO2 amorfo o nanoesponjas de TiO2 cristalino, observándose una mejora significativa de la actividad fotoelectrocatalítica de las nanoestructuras híbridas de TiO2/ZnO electrodepositadas sobre nanoesponjas de TiO2 cristalino. Las nanoestructuras híbridas de TiO2/ZnO sintetizadas tuvieron morfología en forma de nanoesponjas, nanobarras hexagonales, nanobarras sin definir y nanoláminas, estudiando la influencia de la concentración de Zn(NO3)2, temperatura y tiempo durante el proceso de electrodeposición de ZnO sobre su comportamiento como fotoelectrocatalizadores. Las nanoestructuras híbridas de TiO2/ZnO sintetizadas se caracterizaron mediante Microscopía Electrónica de Barrido de Emisión de Campo (FE-SEM), Espectroscopía de Energía Dispersiva de Rayos X (EDX), Microscopía Electrónica de Transmisión (TEM), Microscopía de Fuerza Atómica (AFM), Difracción de Rayos X (DRX), Espectroscopía UV-Visible y mediciones de la banda prohibida. Además, se caracterizaron fotoelectroquímicamente mediante ensayos de rotura de la molécula de agua mediante fotoelectrocatálisis y estabilidad frente a la fotocorrosión y electroquímicamente mediante Espectroscopía de Impedancia Fotoelectroquímica (PEIS) y ensayos de Mott-Schottky. Los resultados evidenciaron que las nanoestructuras híbridas de TiO2/ZnO electrodepositadas sobre TiO2 cristalino a 75 °C durante 15 minutos con una concentración de Zn(NO3)2 de 30 mM fueron las más favorables para llevar a cabo aplicaciones fotoelectroquímicas debido a que ofrecieron buena estabilidad frente a la fotocorrosión, elevada respuesta fotoelectroquímica (177 % superior a la de las nanoesponjas de TiO2), baja resistencia a la transferencia de carga y elevada densidad de portadores de carga, en comparación con las nanoesponjas de TiO2. Por último, las nanoestructuras híbridas de TiO2/ZnO óptimas se emplearon como fotoelectrocatalizadores en aplicaciones energéticas y medioambientales. Por un lado, se evaluó la producción teórica de hidrógeno que se obtendría al utilizar las nanoestructuras híbridas de TiO2/ZnO sintetizadas en la presente Tesis Doctoral como fotoánodos durante el proceso de rotura de la molécula de agua mediante fotoelectrocatálisis. Por otro lado, se evaluó la utilización de las nanoestructuras híbridas de TiO2/ZnO óptimas en la degradación fotoelectrocatalítica de pesticidas (Imazalil) en agua, obteniéndose un porcentaje de degradación del 99.6 % llevando a cabo la degradación fotoelectrocatalítica de 10 ppm de Imazalil en Na2SO4 0.1 M durante 24 horas aplicando un potencial de 0.6 V (Ag/AgCl(KCl 3M)). / [CA] La present tesi doctoral se centra en la síntesi de nanoestructures híbrides de TiO2/ZnO per a utilitzar-les com a fotoelectrocatalitzadors durant la producció d'hidrogen a partir del trencament de la molècula d'aigua mitjançant fotoelectrocatàlisi i la degradació fotoelectrocatalítica de pesticides. El principal avantatge de les nanoestructures híbrides de TiO2/ZnO enfront d'altres fotocatalitzadors basats en materials semiconductors radica en la seua capacitat per a formar heterojuncions en les quals s'intercalen les bandes de valència i conducció de tots dos semiconductors. Aquest fenomen produeix una disminució de l'ample de banda del fotoelectrocatalitzador i dels processos de recombinació dels parells electró-forat fotogenerats, i un augment del rang d'absorció de la llum, la qual cosa millora les seues propietats com a fotoelectrocatalitzadors. Les nanoestructures híbrides de TiO2/ZnO es van sintetitzar mitjançant electrodeposició de ZnO sobre nanosponges de TiO2. Les nanosponges de TiO2 es van formar mitjançant anodització electroquímica de titani en condicions hidrodinàmiques i, posteriorment, es va electrodepositar ZnO sobre la superfície de les nanosponges de TiO2 modificant la concentració del precursor (Zn(NO3)2 0.5-60 mm), la temperatura (25-75 °C) i el temps d'electrodeposició (15-60 min). A més, es va estudiar la influència d'electrodepositar ZnO sobre nanosponges de TiO2 amorf o nanosponges de TiO2 cristal·lí, i es va observar una millora significativa de l'activitat fotoelectrocatalítica de les nanoestructures híbrides de TiO2/ZnO en dur a terme el procés d'electrodeposició de ZnO sobre nanosponges de TiO2 cristal·lí. Les nanoestructures híbrides de TiO2/ZnO sintetitzades van tindre morfologia en forma de nanosponges, nanobarres hexagonals, nanobarres sense definir i nanolàmines, i es va estudiar la influència de la concentració de Zn(NO3)2, la temperatura i el temps durant el procés d'electrodeposició de ZnO sobre el seu comportament com a fotoelectrocatalitzadors. Les nanoestructures híbrides de TiO2/ZnO es van caracteritzar mitjançant microscòpia electrònica d'escombratge d'emissió de camp, espectroscòpia de raigs X per dispersió d'energia, microscòpia electrònica de transmissió, microscòpia de força atòmica, difracció de raigs X, espectroscòpia UV visible i mesuraments de la banda prohibida. D'altra banda, es van caracteritzar fotoelectroquímicament mitjançant assajos de trencament de la molècula d'aigua mitjançant fotoelectrocatàlisi i estabilitat enfront de la fotocorrosió, i electroquímicament mitjançant espectroscòpia d'impedància fotoelectroquímica i assajos de Mott-Schottky. Els resultats van evidenciar que les nanoestructures híbrides de TiO2/ZnO electrodepositades sobre TiO2 cristal·lí a 75°C durant 15 minuts amb una concentració de Zn(NO3)2 de 30 mm van ser les més favorables per a dur a terme aplicacions fotoelectroquímiques, pel fet que van oferir bona estabilitat enfront de la fotocorrosió, elevada resposta fotoelectroquímica (un 177 % superior a la de les nanosponges de TiO2), baixa resistència a la transferència de càrrega i elevada densitat de portadors de càrrega, en comparació amb les nanosponges de TiO2. Finalment, les nanoestructures híbrides de TiO2/ZnO òptimes es van emprar com a fotoelectrocatalitzadors en aplicacions energètiques i mediambientals. D'una banda, es va avaluar la producció teòrica d'hidrogen que s'obtindria en utilitzar les nanoestructures híbrides de TiO2/ZnO sintetitzades en la present tesi doctoral com a fotoànodes durant el procés de trencament de la molècula d'aigua mitjançant fotoelectrocatàlisi. D'altra banda, es va avaluar la utilització de les nanoestructures híbrides de TiO2/ZnO òptimes en la degradació fotoelectrocatalítica de pesticides (Imazalil) en aigua, i es va obtenir un percentatge de degradació del 99.6% duent a terme la degradació fotoelectrocatalítica de 10 ppm d'Imazalil en Na2SO4 0.1 M durant 24 h aplicant un potencial de 0.6 V (Ag/AgCl(KCl 3M)). / [EN] This Doctoral Thesis focuses on synthesizing TiO2/ZnO hybrid nanostructures to be used as photoelectrocatalysts in energy and environmental applications, particularly hydrogen production from water splitting by photoelectrocatalysis and photoelectrocatalytic degradation of pesticides. The main advantage of TiO2/ZnO hybrid nanostructures over other photocatalysts based on semiconductor materials is their ability to form heterojunctions in which the valence and conduction bands of both semiconductors are intercalated. This phenomenon produces a decrease in the band gap of the nanostructures, the recombination processes of the photogenerated electron-hole pairs, and an increase in the light absorption range, which improves their properties as photoelectrocatalysts. The TiO2/ZnO hybrid nanostructures formed in this Doctoral Thesis were synthesized by electrodeposition of ZnO on TiO2 nanosponges. First, TiO2 nanosponges were formed by electrochemical anodization of titanium under hydrodynamic conditions (3000 rpm) and, subsequently, ZnO was electrodeposited on the surface of the TiO2 nanosponges by modifying the precursor concentration (Zn(NO3)2 0.5 - 60 mM), the temperature (25 - 75 °C) and the electrodeposition time (15 - 60 min). In addition, the influence of performing the ZnO electrodeposition on amorphous TiO2 nanosponges (before the thermal treatment) or crystalline TiO2 nanosponges (after the thermal treatment) was studied, showing a significant improvement in the photoelectrocatalytic activity of TiO2/ZnO hybrid nanostructures by carrying out the ZnO electrodeposition process on crystalline TiO2 nanosponges. In this Doctoral Thesis, TiO2/ZnO hybrid nanostructures with morphologies of nanosponges, hexagonal nanorods, undefined nanorods, and nanosheets were synthesized by studying the influence of Zn(NO3)2 concentration, temperature and time during the ZnO electrodeposition process. In addition, the performance of TiO2/ZnO hybrid nanostructures as photoelectrocatalysts was studied. The synthesized TiO2/ZnO hybrid nanostructures were characterized morphologically, photoelectrochemically, and electrochemically. On the one hand, they were morphologically characterized by Field Emission Scanning Electron Microscopy (FE-SEM), Energy Dispersive X-ray Spectroscopy (EDX), Transmission Electron Microscopy (TEM), Atomic Force Microscopy (AFM), Diffraction X-Ray (XRD), UV-Visible Spectroscopy and band gap measurements. On the other hand, they were characterized photoelectrochemically by e water splitting and stability against photocorrosion tests and electrochemically by Photoelectrochemical Impedance Spectroscopy (PEIS) and Mott-Schottky tests. The results showed that TiO2/ZnO hybrid nanostructures electrodeposited on crystalline TiO2 at 75 °C for 15 minutes with a Zn(NO3)2 concentration of 30 mM were the most favourable for carrying out photoelectrochemical applications because they offered good stability against photocorrosion, high photoelectrochemical response (177 % higher than that of TiO2 nanosponges), low resistance to charge transfer and high density of charge carriers, compared to TiO2 nanosponges. Finally, the optimal TiO2/ZnO hybrid nanostructures were used as photoelectrocatalysts in energy and environmental applications. On the one hand, the theoretical hydrogen production obtained with the TiO2/ZnO hybrid nanostructures synthesized in this Doctoral Thesis during the water splitting tests was evaluated. On the other hand, the use of the optimal TiO2/ZnO hybrid nanostructures as photoelectrocatalysts in the photoelectrocatalytic degradation of pesticides (Imazalil) in water was evaluated, obtaining a degradation percentage of 99.6 % carrying out the photoelectrocatalytic degradation of 10 ppm of Imazalil in Na2SO4 0.1 M for 24 hours applying a potential of 0.6 VAg/AgCl (3M KCl). / Agradezco al Ministerio de Ciencia e Innovación la concesión de la subvención proporcionada por el Sistema Nacional de Garantía Juvenil (PEJ2018- 003596-A-AR), al Ministerio de Economía, Industria y Competitividad la concesión del proyecto CTQ2016-79203-R y al Ministerio de Ciencia e Innovación/Agencia Estatal de Investigación la concesión del proyecto PID2019-105844RB- I00/MCIN/AEI/ 10.13039/501100011033, en los cuales he podido participar durante el desarrollo de la presente Tesis Doctoral. / Navarro Gázquez, PJ. (2023). Desarrollo de nuevos electrodos basados en nanoestructuras híbridas de óxidos metálicos semiconductores para aplicaciones energéticas y medioambientales [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/194708