PhD Thesis Defence Presentations - Bjorn Hasa

The research conducted for this dissertation involves experiments in the field of electrochemistry and catalysis. Initially, a series of electrochemical reactions are conducted to examine our modified Pt-catalysts as well as the interaction of metal particles (Pt-Ru) with different carbon supporters. Then, those catalysts are studied as anodes electrodes of a membrane electrode assembly (MEA) during the operation of a PEM Fuel Cell or Electrolyzer. Additionally, the comparison of different substrates using Pt or Pt-Ni catalysts is evaluated by hydrogen evolution reaction (HER). Finally, the electrochemical promotion of catalysis (EPOC) is studied in an alkaline solution.

In the first chapter is described the modification of Pt-based anodic electrodes with different metals in order to have better activity during alcohol oxidation. The aim of this chapter is to understand the role of the modification of Pt with another metal (i.e. Ir or SnO₂) and to explain the role of TiO₂ in binary (Pt-TiO₂) or ternary (Pt-Ru-TiO₂) electrodes. 

In the second chapter the electrochemical experiments are carried out in a rotating disk electrode (RDE). The rotating disc electrode (RDE) is the classical hydrodynamic electroanalytical technique used to limit the diffusion layer thickness. Apart from the electrochemical and physicochemical methods, there is an extensive description of the catalysts preparation and carbon supporters. 

The third chapter is dedicated to a detailed description of fuel cell technology. The main categories of fuel cells and stacks components are briefly described. An extensive description of a PEM fuel cell operation using either hydrogen, methanol, or ethanol is shown. 

In the fourth chapter the electrochemical reforming of methanol and ethanol for hydrogen production using the catalysts of the first chapter is investigated. In this chapter hydrogen production methods as well as its storage and transport are described. The electrolysis process is carried out in a Polymer Electrode Membrane (PEM) electrolyzer. PEM is comprised of a Pt-Ru with modified TiO₂ anode, a commercial Pt/C cathode, and a Nafion 117 electrolyte. 

In the fifth chapter, a series of Pt or Pt–Ni alloy catalysts on different substrates are synthesized by potentiostatic electrodeposition, and the optimum deposition parameters are determined by scanning electron microscopy (SEM). The effect of electrodeposition parameters on the morphology, composition, and electrocatalytic activity for Hydrogen Evolution Reaction (HER) is investigated. 

In the last chapter, we examine the effect of electrochemical promotion of catalysis (EPOC) on commercial M (M=Pt, Rh, Pd)/Vulcan XC72 (E-tek) electrodes in alkaline media. Various reactant mixtures (H₂ and O₂) are fed simultaneously through a glass frit to the anodic electrode.