A Density Functional study on the Reactivity Enhancement Induced by Gold in IrAu Nanoalloys

CAPPELLARI, PAULA S.; SOLDANO, GERMÁN J.; MARISCAL, MARCELO M.

Congreso; VI San Luis Conference; 2018

Nanoalloys(NA) are innovative materials with diverse and novel propertiescompared to its bulk counterpart.The essential characteristics of NA, depend on the method and theconditions in which they are synthesized. Animprovement in their properties is generally observed due tosynergistic effects upon alloy.The synergy between both metals, modulated by the different NAstructural arrangements, introduces a large diversity in reactivity,mainly due to the electronic tuning of metals.Aboutthis, IrAu NAhave proved remarkable reactivity for several reactions.Inthis work, mixed IrAu NAof 48 total atoms were studied in different atomic compositions (IrmAun)using Density Functional Theory (DFT). A notable tendency tosegregation is observed, where Ir atoms are located in the inner partand Au atoms in the outermost region of the nanostructure. We foundthat IrAu nanoalloys present a distinctive synergistic effect withrespect to reactivity. Iratoms maintain their structural ordering in the IrAu NA in contrastwith Au atoms which are packed in a disordered arrangement. In fact,this results could complement the interpretation of the experimentalanalysis of STEM images previouslyreported.Despitethe experimental evidence on the synergic effect between iridium andgold in nanoalloys, a systematic first principle study of suchsystems and moreover, a fundamental understanding of the physicalpicture behind this phenomena, is still missing. Inaddition, the projected density of electronic states (PDOS) energieswere analyzed by examining the d-band shift to estimate thereactivity of various IrAu NA.Thislatter was also evaluated using CO as a probe molecule, comparing itsadsorption energy on IrAu NA and the corresponding pure metalclusters. TheDFT results foundinthis studyrevel an improvement in the reactivity of Ir by Au atoms alreadyevidenced experimentally and successively by means of the study ofPDOS the reason for it could be understood.In this sense, the addition of Au atoms to Ir clusters increases thereactivity of Ir by generating unoccupied orbital near the Fermilevel indicated through the PDOS study. Thisfactwas confirmed using CO as a probe molecule. These findings open upnew possibilities to explode the catalytic potential of greattechnological interest in mixed systems IrAu.p { margin-bottom: 0cm; direction: ltr; color: rgb(0, 0, 0); text-align: justify; }p.western { font-family: "CMR10", "Times New Roman"; font-size: 11pt; }p.cjk { font-family: "SimSun", "宋体"; font-size: 11pt; }p.ctl { font-family: "CMR10", "Times New Roman"; font-size: 10pt; }a:link { color: rgb(5, 99, 193); }