Kinetics of hydrogen adsorption and desorption on platinum catalyst

Poraba energije po vsem svetu vztrajno narašča, kar vodi v neizogibno izčrpavanje obstoječih virov energije, zato je ključno iskanje novih virov energije. Kot potencialni nosilec energije v prihodnosti, ima vodik pomembno vlogo na poti proti nizkoogljičnemu gospodarstvu. Zaradi svojih edinstvenih fizikalno-kemijskih lastnosti je platina pomemben element v tehnologijah, ki uporabljajo protonsko izmenjevalno membrano (PEM), ki se že uporablja tako v elektrolizerjih za proizvodnjo vodika kot tudi v vodikovih gorivnih celicah. Platina zato predstavlja ključ do brezemisijskega potenciala vodika. V magistrskem delu sem določevala kinetiko adsorpcije in desorpcije vodika na platinski katalizator Pt/SiO2, ki sem ga sintetizirala po metodi močne elektrostatske adsorpcije. Sintetizirani katalizator sem okarakterizirala z različnimi analiznimi tehnikami, in sicer z EDS, ICP OES, XRPD, TEM in TPD. S spreminjanjem temperature pri termični obdelavi sem pripravila različno velike platinske nanodelce na nosilcu za določitev vpliva velikosti nanodelcev na adsorpcijo vodika. Pri višjih temperaturah termične obdelave so nastali večji nanodelci, posledično pa se je na katalizator adsorbiralo manj vodika. Temperaturni maksimum desorpcijskega vrha nekoliko zavisi od hitrosti segrevanja in je pri hitrosti segrevanja 10 °C/min pri 190 °C. Hitrost adsorpcije je v temperaturnem območju med 0 °C in -100 °C temperaturno neodvisna, delež adsorbiranega vodika pa se ni bistveno spremenil. Rezultati kinetičnega modela so pokazali, da je množina aktivnih mest večja pri katalizatorju z manjšo velikostjo platinskih nanodelcev. Aktivacijska energija desorpcije je enaka 17 kJ/mol, kar je manj od pričakovane vrednosti, zato bi bilo kinetični model v prihodnje potrebno izboljšati.Energy consumption worldwide is steadily increasing which leads to an inevitable depletion of existing energy sources. Therefore, there is an ever-increasing demand for new sources of energy. Being a potential energy carrier of the future, hydrogen plays an important role in the path toward a low-carbon economy. Having unique chemical and physical properties, platinum is an important element of proton exchange membrane (PEM) technology, which is already in use in both electrolyzers to produce hydrogen and in hydrogen fuel cells and thus holds great promise in unlocking the zero-emission potential of hydrogen. In my master\u27s thesis I was determining kinetics of hydrogen adsorption and desorption on a platinum catalyst Pt/SiO2 synthesized using a strong electrostatic adsorption method. The synthesized catalyst was characterized by various analytical techniques, such as EDS, ICP-OES, XRPD, TEM and TPD. By varying the calcination temperature, platinum nanoparticles of different sizes on the support were generated, in order to determine the influence of nanoparticle size on hydrogen adsorption. At higher calcination temperatures, larger nanoparticles were formed and as a consequence, less hydrogen adsorbed onto the catalyst. The temperature maximum of the desorption peak depends on the heating rate and is at 190 °C for a heating rate of 10 °C/min. The adsorption rate is temperature-independent in the temperature range between 0 °C and -100 °C, and the proportion of adsorbed hydrogen did not change significantly. The result of the kinetic model showed that the number of active sites is greater for the catalyst containing smaller platinum nanoparticles. The activation energy of desorption is 17 kJ/mol, which is lower than the expected value, therefore, the kinetic model should be improved in the future