Pt-zko katalizatzaileen dopaketa desaktibazioa murrizteko

Abstract

[EU]CO-ren bidezko pozoiketak arazo larria suposatzen du Pt-zko katalizatzaileen garapenerako. Pt katalizatzaile oso eraginkorra izan arren erreakzio askotarako, oso erraz desaktibatzen da CO-ren presentzian. CO sendoegi lotzen da Pt-ra eta leku aktiboen blokeatzen ditu. Arazoari argi gehiago igortzeko katalizatzailearen egitura elektronikoaren ezagutza sakon bat behar da. Lan honetan MgO(100) gainazalean adsorbatutako Pt2X-CO klusterrak erabili dira. Lau dopatzaile ezberdin propasatzen dira: Al, B, Ge eta Si. PW-DFT kalkuluak burutu dira adsortzio energiak, bader-en kargak, surface electrostatic potential eta projected density of states lortzeko. Aurkitu da Bader-en kargak eta surface electrostatic potential ez direla nahikoak CO-ren adsortzio indarra guztiz azaltzeko. Bestetik, projected density of states analisiak erakusten du dopatzaileak CO-ren HOMO-tik Pt dz2 -rako donazioa erreduzitzen duela karga transferituz Pt dz2 -ra. Honek eragiten du Pt-C lotura ahultzea eta hortaz, CO adsortzio energia txikitzea. Karga transferentzia hauek intentsoak dira Ge eta Si-ren kasuan batez ere. Dopatzaileak eragina du adsortzio geometrian. Modu honetara, MgO(100) gainazaletik CO-ren LUMO-ra ematen den karga transferentzia handitu edo txikikitu dezake. Emaitza hauek CO-ren adsortzio energiekin korrelazionatzen dira. Erakutsi da Pt klusterraren dopaketak bidea irekitzen duela katalizatzaile eraginkor eta industria berdeago baten garapenerako.

[EN]CO poisoning has become a great drawback in the development of more efficient Pt catalysts. Despite being applicable to a great variety of reactions, it is quickly deactivated in the presence of CO. CO binds very strongly and blocks the active sites. To shed more light in the matter a deep understanding of the catalyst’s electronic structure is needed. MgO(100) supported Pt2X-CO clusters are used. We propose four different dopants : Al, B, Ge and Si. Adsorption energies, Bader charges, surface electrostatic potential and projected density of states are calculated using PW-DFT techniques. It is observed that Bader charges and surface electrostatic potential are insuffient to explain all adsorption energy trends. On the other hand, projected density of states resuls show that upon doping, donation from CO HOMO to Pt dz2 is reduced as the dopant donates charge to dz2 . Consequently, Pt-C bond is weakened and CO adsorption energy is reduced. This behaviour is especially significant in Ge and Si. Moreover, the dopant has a significant effect in the adsorption geometry. Therefore, charge transfer from MgO(100) surface to CO LUMO might be affected. These results correlate with CO adsorption energies. All in all, it is shown that doping Pt clusters will open new opportunities for the development of more efficient Pt catalysts and a greener industry.