In Situ Characterizations of Nanostructured SnO_x/Pt(111) Surfaces Using Ambient-Pressure XPS (APXPS) and High-Pressure Scanning Tunneling Microscopy (HPSTM)

Abstract

We have conducted in situ measurement of "inverse catalysts" of SnO x nanostructures supported on Pt(111) using ambient-pressure X-ray photoelectron spectroscopy (APXPS) and high-pressure scanning tunneling microscopy (HPSTM) techniques under CO exposure at room temperature and 450 K. Nanostructures of SnO x were prepared by depositing Sn on Pt(111) precovered by O 2 layers at liquid nitrogen temperature. APXPS data show that the prepared SnO x nanoparticles are highly reduced, with Sn 2+ being the dominant oxide species. The relative Sn 2+ concentration, compared to Sn 4+ and Sn 0 , in the SnO x nanoparticles decreases slightly with increasing Sn coverage. In situ study of SnO x /Pt(111) inverse catalyst shows that for lower coverage of SnO x (0.25 monolayers (ML)), the amount of Sn 2+ decreased steadily, while Sn 0 amount steadily increased with negligible Sn 4+ amount, as the surface was heated under CO exposure at 450 K. Meanwhile, for the higher coverage (1.0 ML), the decrease of Sn 2+ is followed by sharp increase in the amount of Sn 4+ and Sn 0 . HPSTM images show that small islands of SnO x are randomly formed on the substrate, with the size and density increasing with SnO x coverage. HPSTM images show morphology differences between low and high coverages of SnO x on Pt(111) under both UHV and CO exposure conditions.

Sn2+-Doped Double-Shelled TiO2 Hollow Nanospheres with Minimal Pt Content for Significantly Enhanced Solar H2 Production

“…As shown in Figure , the Sn 3d 5/2 signal at ca. 486 eV can be deconvoluted by Gaussian function into two parts at 485.8 and 487.1 eV, which were assigned to Sn 2+ and Sn 4+ , respectively. − The ratio of Sn 2+ to the whole Sn species in DHS–PtSn 2+ was estimated to be ca. 83.6%.…”

Highly Oxidized Platinum Nanoparticles Prepared through Radio‐Frequency Sputtering: Thermal Stability and Reaction Probability towards CO

“…Supported platinum particles are widely appliedf or various reactions of oxidation (CO, [1,2] hydrocarbons, [3] alcohols [4] ), hydrogenation, [5] cracking, [6] isomerization, [7] and so forth. The investigation of models ystems, [8,9] frequently applied in the case of platinum-containing catalysts, [10][11][12][13] plays ac rucial role in understanding reactionm echanismso nt he surface of real catalysts.…”

Using “Tender” X-ray Ambient Pressure X-Ray Photoelectron Spectroscopy as A Direct Probe of Solid-Liquid Interface

“…By pushing the operating pressure to higher values, these developments have transformed XPS from a surface science technique in vacuum to an important in situ tool for studies at solid-gas interfaces. Currently, AP-XPS is utilized in many important research fields such as heterogeneous catalysis, fuel cell, batteries, and environmental science 11 12 13 14 15 16 17 18 19 20 21 . Despite these achievements, some of the most important physical and chemical processes in nature, particularly in electrochemistry, take place at interfaces between solid-liquid phases.…”