Arüülkilede ja nanokomposiitmaterjalidega modifitseeritud süsinik- ja metallelektroodide pinna ja elektrokeemiliste omaduste karakteriseerimine

Väitekirja 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

Data of one-dimensional polymer-derived ceramic nanowires with electrocatalytically active metallic silicide tips as cathode catalysts for Zn–air batteries

This dataset contains the data presented in the figures of pulbished paper "One-dimensional polymer-derived ceramic nanowires with electrocatalytically active metallic silicide tips as cathode catalysts for Zn–air batteries" RSC Advances 11 39707 (https://doi.org/10.1039/D1RA05688C) The electrochemical characterisation data, which was measured in University of Tartu Institute of Chemistry, is for Figures 5, 7, S5-S7 and the nomenclature of the catalysts is the same as in the mentioned article

Effect of carbon support and metal in M-N-C catalysts on the ORR activity and stability for HT-PEMFC application

Metal-nitrogen-carbon (M-N-C) catalysts are one of the most promising alternatives to Pt catalysts for the oxygen reduction reaction (ORR) in acidic electrolytes. Especially in the high-temperature proton exchange membrane fuel cell (HT-PEMFC) the use of M-N-Cs is attractive as they are in contrast to Pt not negatively affected by the phosphoric acid electrolyte. However, they show lower activity and stability compared to Pt catalysts, making further optimization mandatory. The poster presentation will give an overview of different approaches to increase the activity and stability of M-N-Cs for HT-PEMFC. This includes the investigation of the effect of different carbon supports as well as the impact of single- and dual-metal sites. As carbon support for Fe-N-Cs, black pearls were compared with phosphoric acid-activated biomasses from coconut shells and rye straw. A promising stability of biomass-based Fe-N-Cs was found by rotating disc electrode measurements in perchloric acid. While the black pearl-based Fe-N-C displays a mass activity (MA) loss of 63 %, the biomass-based Fe-N-Cs show only MA losses of around 35 % after 5000 cycles between 1.0-1.5 VRHE. However, low stability independent of the carbon support was observed in HT-PEMFC. Next to the support-based synthesis a metal-organic framework (MOF) based M-N-C synthesis was used to investigate the effect of the metal site. Different metals including Fe, Co and Sn as single atom (SAC) or dual atom catalysts (DAC) were tested in phosphoric acid electrolyte and compared with the Fe-N-Cs from support-based synthesis. The DAC containing Fe and Sn (1:1) showed an outstanding MA at 0.8 VRHE of 4.7 A g-1 compared to a commercial Fe-N-C catalyst (PMF 011904, Pajarito Powder) with an MA of 2.8 A g-1. Further studies will include the comparison of SAC and DAC stability in HT-PEMFC

Data of tuning NiCo2O4 bifunctionality with nitrogen-doped graphene nanoribbons in oxygen electrocatalysis for zinc-air battery application

This dataset contains the data presented in the figures of pulbished paper "Tuning NiCo2O4 bifunctionality with nitrogen-doped graphene nanoribbons in oxygen electrocatalysis for zinc-air battery application" Journal of Electroanalytical Chemistry 928 117000 (https://doi.org/10.1016/j.jelechem.2022.117000) The electrochemical characterisation data, which was measured in University of Tartu Institute of Chemistry, is for Figures 6, 7, S17 and the nomenclature of the catalysts is the same as in the mentioned article

Data of outstanding platinum group metal-free bifunctional catalysts for rechargeable zinc-air batteries

This dataset contains the data presented in the figures of pulbished paper "Outstanding platinum group metal-free bifunctional catalysts for rechargeable zinc-air batteries" Electrochimica Acta 446 142126 (https://doi.org/10.1016/j.electacta.2023.142126) The electrochemical characterisation data, which was measured in University of Tartu Institute of Chemistry, is for Figures 2, 3, 4, 5, 6 and the nomenclature of the catalysts is the same as in the mentioned article

Data of polypyrrole and polythiophene modified carbon nanotube-based cathode catalysts for anion exchange membrane fuel cell

This dataset contains the data presented in the figures of pulbished paper "Polypyrrole and polythiophene modified carbon nanotube-based cathode catalysts for anion exchange membrane fuel cell" ChemElectroChem 9 e202200161 (https://doi.org/10.1002/celc.202200161) The electrochemical characterisation data, which was measured in University of Tartu Institute of Chemistry, is for Figures 1,2,3a,4a, 9, S1 and the nomenclature of the catalysts is the same as in the mentioned article

Data of transition metal phthalocyanine-modified shungite-based cathode catalysts for alkaline membrane fuel cell

This dataset contains the data presented in the figures of pulbished paper "Transition metal phthalocyanine-modified shungite-based cathode catalysts for alkaline membrane fuel cell" International Journal of Hydrogen Energy 46, 4365-4377 (https://doi.org/10.1016/j.ijhydene.2020.10.231) The electrochemical characterisation data, which was measured in University of Tartu Institute of Chemistry, is for Figures 5, 6, 7, 9, 10, S2, S3, S4 and the nomenclature of the catalysts is the same as in the mentioned article

Data of electrospun carbon nanofibre-based catalysts prepared with Co and Fe phthalocyanine for oxygen reduction in acidic medium

This dataset contains the data presented in the figures of pulbished paper "Electrospun Carbon Nanofibre-Based Catalysts Prepared with Co and Fe Phthalocyanine for Oxygen Reduction in Acidic Medium" ChemElectroChem, e202300131 (https://doi.org/10.1002/celc.202300131). The electrochemical characterisation data, which was measured in University of Tartu Institute of Chemistry, is for Figures 1, 2, 4, 5, 6 and the nomenclature of the catalysts is the same as in the mentioned article