Pt-zko katalizatzaileen dopaketa desaktibazioa murrizteko
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Date
2020-10-16Author
Ugartemendia Biurrun, Andoni
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[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.