Master Thesis: Development and characterization of nanostructured oxygen electrocatalysts for anode of PEM electrolyzer

Abstract

This thesis mainly focuses on developing highly active and stable anode catalysts for polymer electrolyte membrane electrolyzer by the means of using one aerogel substrate material and optimizing thermal treatment protocols. Here we focus on the iridium based catalyst since it is still the best feasible oxygen evolution reaction (OER) catalysts in acid medium so far. In this thesis, two strategies were applied to achieve this goal: i) nanosized iridium particles were dispersed on porous aerogel antimony- or niobium-doped tin dioxide (ATO or NTO); ii) different thermal treatment protocols were used for bimetallic IrRu. Catalysts were prepared using wet chemical synthesis method by reducing IrCl3 or RuCl3 in anhydrous ethanol. By adding aerogel support and introducing vanadium, the mass activity and stability of the catalyst were improved. Electrochemical characterization, such as cyclic voltammogram (CV), chronopotentiometry, chronoamperometry and electrochemical impedance spectroscopy (EIS) were used for evaluating its electrochemical performance; SEM and EDX were carried out to analyze the morphologies and elements distribution of the catalysts. In addition, copper under potential deposition (Cu-UPD) on supported iridium catalysts was performed to determine the number of surface iridium atoms available for electrochemical reaction. Furthermore, bimetallic IrRu catalyst was thermally treated using various thermal treatment protocols and evaluated electrochemically by cyclic voltammogram. The results reveal that the aerogel supported catalysts possess superior electrochemial properties, either activity or stability, comparing to state of the art unsupported iridium catalyst. And also the thermally treated iridium-ruthenium oxide exhibits different OER performances when they were applied under different thermal treatment temperatures.