1 research outputs found
XPS Study of Stability and Reactivity of Oxidized Pt Nanoparticles Supported on TiO<sub>2</sub>
The method of X-ray photoelectron
spectroscopy was used to study
the interaction of the model Pt/TiO<sub>2</sub> catalysts with NO<sub>2</sub> and the following reduction of the oxidized Pt nanoparticles
in vacuum, hydrogen, and methane. It was shown that, while interacting
with NO<sub>2</sub> at room temperature, the metal Pt nanoparticles
transform, first, into the phase which was tentatively assigned as
particles containing subsurface/dissolved oxygen [Pt-O<sub>sub</sub>], and then, into the PtO and PtO<sub>2</sub> oxides. If only the
first state of platinum [Pt-O<sub>sub</sub>] is formed, it demonstrates
exclusively high reactivity toward hydrogen. For the samples containing
simultaneously [Pt-O<sub>sub</sub>], PtO, and PtO<sub>2</sub>, the
highest reaction ability was demonstrated by PtO<sub>2</sub>; contrary
to the other two oxidized states, it is reducing while kept in vacuum
under X-ray irradiation. All three coexisting states of the oxidized
platinum can be reduced when heated in vacuum as well as while interacting
with hydrogen at room temperature. First, PtO<sub>2</sub> is reduced
to PtO. PtO and [Pt-O<sub>sub</sub>] begin being reduced after the
complete consumption of PtO<sub>2</sub>. We propose that, when a sample
contains simultaneously all three states of oxidized platinum, the
supported particles have a core–shell structure with a nucleus
of perturbed platinum containing oxygen atoms, which are covered with
a film of Pt oxides. It was shown that none of the oxidized states
of platinum react with methane at room temperature