CO-induced restructuring of Pt(110)-(1×2): Bridging the pressure gap with high-pressure scanning tunneling microscopy

Abstract

We present an extensive investigation of CO-induced structural transformations occurring on the reconstructed Pt(110)-(1×2) surface while bridging the so-called pressure gap between surface science and industrial catalysis. The structural changes are followed on the atomic scale as a function of CO pressure over 12 orders of magnitude, up to 1 bar, by the use of a novel high-pressure scanning tunneling microscope (HP-STM). The transition between the low-coverage and saturation-coverage structures is found to proceed through local displacements of substrate Pt atoms. The structural transformations of the Pt surface as observed by STM can be explained within a very simple picture governed by the gain in CO binding energy when CO binds to low-coordinated metal atoms.

Looking at Heterogeneous Catalysis at Atmospheric Pressure Using Tunnel Vision

“…of CO on Pt(111) [45,46], and of CO and NO on Rh(111) [47][48][49]. Also, gas-phase-induced restructuring of metal surfaces has been observed by HP-STM, for example of Pt(110)-1 · 2 in CO [50], H 2 and O 2 [51], and of Cu(110)-1 · 1 in H 2 [52]. Supported gold nanoparticles in TiO 2 have been studied in mixtures of CO and O 2 over a wide pressure range [53].…”

“…This surface has been studied at high gas pressures with STM by at least three research groups [13,50,51]. Under UHV conditions, it exhibits the so-called 1 · 2 missingrow reconstruction, in which every second atom row along the close-packed " 110 Â Ã direction is absent.…”

Coverage-dependent molecular tilt of carbon monoxide chemisorbed on Pt{110}: A combined LEED and DFT structural analysis

“…in the automotive three-way catalyst where it catalyzes the oxidation of uncombusted hydrocarbons and carbon monoxide [1]. In particular, adsorption on the Pt{110} surface has been the subject of various theoretical and experimental investigations in the modern surface science era because it represents a prototype for adsorbate-induced structure transformations in an ultrahigh vacuum environment (UHV) with dramatically changing reactivities depending on the structure of the substrate [2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33]. The clean Pt{110} surface exhibits a p(1 × 2) "missing row" reconstructed phase, where every second row in the [001] direction is missing [4,18,26].…”

Theory of orthogonal interactions of CO molecules on a one-dimensional substrate

“…For a substrate with under-coordinated atoms [11][12][13] , such as a reconstructed surface containing some empty sites, the situation becomes more complicated and the above picture may need some modification. The first consideration is the extra degrees of freedom: in the presence of under-coordinated atoms, there are multiple nonequivalent sites for the adsorption to take place, which opens the possibility of adsorption induced surface reconstruction.…”

“…The surface reconstruction involves breaking original bonds and costs energy but, as mentioned previously, the adsorption is typically of the largest energy scale which determines the surface reconstruction. A typical example is CO adsorption on Pt(110) (1 × 2) reconstructed surface, where energy gain of CO binding at low coordination sites leads to step formation 11,12 . The second consideration is that the dispersion of surface electrons can be highly anisotropic, i.e., more one-dimensional (1D), because with under-coordinated atoms it is more difficult for electrons to hop across the empty sites.…”