Phase-Dependent Formation of Coherent Interface Structure between PtO₂ and TiO₂ and Its Impact on Thermal Decomposition Behavior

Abstract

This study investigated the thermal decomposition behaviors of platinum oxide (PtO2) nanoparticles deposited on polycrystalline TiO2 in different crystal phases. The dissociation of PtO2 to metallic platinum in air occurred at 400 °C on anatase TiO2 (Pt/TiO2-A), but required 650 °C or higher on rutile TiO2 (Pt/TiO2-R). The higher thermal stability of PtO2 on rutile TiO2 is caused by thermodynamic effect and rather than kinetic effect. In contrast to the thermodynamic prediction, metallic Pt (Pt0) on TiO2-R was reversibly oxidized to PtO2 (Pt4+) at 650 °C. This behavior was attributed to the coherent interface structure formed by strong interactions between PtO2 and rutile TiO2, as revealed by combined extended X-ray adsorption spectroscopy (EXAFS) and density functional theory (DFT) studies. At the optimized interface structure, between the (100) planes of α-PtO2 and rutile TiO2, the interface formation energy was −17.04 kJ mol–1 Å–2 versus −9.84 kJ mol–1 Å–2 in the anatase TiO2 model. The larger interface formation energy provides a stabilizing effect against PtO2 dissociation. Therefore, the widely used Pt-loaded rutile TiO2 typifies the interfacial interactions under an oxidizing atmosphere, which differ from the strong metal–support interactions prevailing under a reducing atmosphere.

Carbon nanotube supported PtO nanoparticles with hybrid chemical states for efficient hydrogen evolution

“…2(b and c), respectively. The EXAFS curve for PtO x /CNT shows a main peak at 1.6 Å for Pt-O bonds and a broad feature at around 2.8-3.3 Å for the second neighboring Pt-Pt distance [31][32][33]. The curve is similar to that for PtO 2 but with lower peak intensities, suggesting an oxidized state of Pt II as identified by XPS.…”

Atomic-scale structure and chemical sensing application of ultrasmall size-selected Pt nanoparticles supported on SnO2

“…This observation reminds of a recent study demonstrating coherent interfaces between PtO 2 nanoparticles and rutile TiO 2 supports. 66 Similarly, an epitaxial relationship between CuO nanowire supports and Pd nanoparticles after thermal oxidation has been identified, resulting from an interface-driven oxidation mechanism. 67 PdO nanoparticles epitaxially aligned to MgO substrates have also been found, but their formation was explained by PdO nanoparticle nucleation and growth enabled by Pd surface diffusion.…”

“…In addition to size-and shapedependent effects, 51,73 such strong nanoparticle-support interactions play an important role for nanocatalyst reactivity and thermal stability. 66,74 The question arises which Pt oxide phase was formed on the SnO 2 support and how this would influence the chemoresistive sensing properties of the SnO 2 -Pt devices presented above. The nanoparticle lattice spacings observed in our high-resolution TEM analysis were in good agreement with Pt 3 O 4 and b-PtO 2 phases.…”

“…The nanoparticle lattice spacings observed in our high-resolution TEM analysis were in good agreement with Pt 3 O 4 and b-PtO 2 phases. The authors of Nur et al, 66 have argued that, despite the similar crystal structures of their rutile TiO 2 support and b-PtO 2 , the occurrence of the latter is not expected as the synthesis of this phase typically requires high temperatures and pressures. Further, Pt 3 O 4 was formed during the oxidation of Pt nanoparticles supported on MgO 75 and on carbon, 76 whereas no b-PtO 2 was identified.…”

Heat- and corrosion-resistant catalytic materials for environmental and energy applications

“…This stark contrast can be attributed to the greater interfacial formation energy, which stabilizes the oxidized states of Pt on rutile. 34) During continuous catalytic testing for 1,000 h at 600°C, Pt/anatase exhibited activity loss of approximately 4 % (from the initial activity). The most stable SO 3 decomposition performance at 600°C was reported to be that of Pt supported on Ta 2 O 5 .…”