26. augustil kell 10.15 kaitseb Marek Mooste oma doktoritööd „Surface and electrochemical characterisation of aryl film and nanocomposite material modified carbon and metal-based electrodes” (“Arüülkilede ja nanokomposiitmaterjalidega modifitseeritud süsinik- ja metallelektroodide pinna ja elektrokeemiliste omaduste karakteriseerimine“). Doctor of Philosophy (PhD) kraadi saamiseks keemia erialal.
On 26 august at 10:15 Marek Mooste will defend his doctoral thesis „Surface and electrochemical characterisation of aryl film and nanocomposite material modified carbon and metal-based electrodes” for obtaining the degree of Doctor of Philosophy (in chemistry).
Associate Professor Kaido Tammeveski (PhD), Institute of Chemisrty, University of Tart
Research Fellow Elo Kibena-Põldsepp (PhD), Institute of Chemisrty, University of Tart
Professor Lasse Murtomäki, University of Aalto, Finland
The 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.