Doctoral defence: Peeter Valk "Methanol oxidation on platinum-rare-earth metal oxide activated catalysts“

On 31 August at 10:15  Peeter Valk will defend his doctoral thesis "Methanol Oxidation on Platinum-Rare-Earth Metal Oxide Activated Catalysts“ for obtaining the degree of Doctor of Philosophy (in Chemistry).

Supervisors:

Associate Professor in Physical and Electrochemistry Jaak Nerut, University of Tartu

Professor of Physical Chemistry Enn Lust, University of Tartu

Opponent:

Mihails Kusnezoff, Fraunhofer Institute for Ceramic Technologies and Systems (Germany)

Summary

Fuel cells are promising devices for the production of green energy. While green hydrogen is quite common, green methanol can be produced using renewable energy and captured CO2. Hydrogen fuel cells emit only H2O. Methanol fuel cells also emit CO2, which is the same CO2 captured to produce green methanol, so it is essentially a zero-sum game. What is the benefit of a zero-sum game? This only applies to CO2. The benefit comes from storing excess cheap renewable energy in methanol, and using it to produce green electricity, when electricity is scarce and expensive. Fuel cells do not produce dangerous nanoparticles, or NOx or SOx, which cause smog and acid rain. The CO2 from the exhaust of a methanol fuel cell can be recaptured. However, fuel cells depend on Pt catalyst nanoparticles to increase the reaction rate. The smaller the catalyst particles, the higher the surface area on which reactions occur. One of the aims of this work was to make smaller catalyst particles. Various methods exist; for example, using ethylene glycol and a microwave oven to synthesise Pt nanoparticles proved suitable, as well as heating a Pt precursor in hydrogen. Nanoparticles are deposited onto a carbon support material. It plays an essential role in fuel cells: it conducts electricity and allows reagents to flow. High surface area materials developed at the University of Tartu showed good conductivity and durability. While Pt is a good catalyst for methanol oxidation, it holds on to some of the intermediate compounds produced on its surface too strongly. These need to be cleaned from the surface. Ruthenium is one costly option. In this work, cheaper alternatives, such as rare-earth metal oxides, were used. Various methods for synthesising cerium and praseodymium oxide along with Pt were studied. The best results were obtained by heating praseodymium hydroxide to 1100 °C in an inert gas and depositing Pt by heating the material impregnated with Pt precursor in hydrogen at a lower temperature. This material had small, well-dispersed Pt nanoparticles and praseodymium oxide nanorods containing several forms of Pr oxide. These oxides aid methanol oxidation by cleaning the Pt surface. They provide oxygen-containing compounds adsorbed on their surface, which diffuse onto the Pt particle. CO2 forms, leaves the surface, and the green cycle continues.

Defence can be also followed in Teams.