Site Switching and Surface Restructuring Induced by NO Adsorption on Pt{110}

Abstract

We present the first infrared vibrational study of the adsorption of NO on Pt{110} over a wide range of temperatures. Adsorption is strongly dependent on both temperature and coverage, with many different species being formed on the surface. Under all conditions, site switching is observed during NO adsorption: at low coverages bridge-bonded species are formed on the surface, and at very high coverage NO switches to on-top sites. Other species, not previously reported, are also observed, depending on both adsorption temperature and coverage. The clean Pt{110} surface exhibits a (1 × 2) surface reconstruction which can be lifted by the adsorption of NO (or CO), depending on surface temperature and adsorbate coverage. In contrast to CO adsorption, the on-top surface species shows different frequencies on the (1 × 2) and (1 × 1) surface phases, and this is deployed to identify the temperature at which the reconstruction begins to lift.

Surface chemistry of NO and NO2 on the Pt(110)-(1×2) surface: A comparative study

“…These results beautifully illustrate the reversible conversion between bridged NO(a) and linear NO(a) on Pt(1 1 0) driven by the coverage-dependent strong repulsive interactions. Similar phenomenon was previously observed for NO/Pt(1 1 0) by means of infrared vibrational spectroscopy: the bridgebonded species is stable at low coverages, but it converts into the atop species at high coverages [11,18].…”

“…Here we assigned the linear and bridged NO(a) species on Pt(1 1 0)-(1 · 2) simply on basis of the observed N-O vibrational frequencies. Similar site assignments on basis of the vibrational spectroscopy for NO have also been reported before [11,18]. However, vibrational features of adsorbed species, particularly of NO, are not sufficient to make the accurate adsorption site assignments, therefore, the nature of the adsorption sites of NO(a) Pt(1 1 0)-(1 · 2) on need to be verified by further structural measurements.…”

“…(1 · 1) structural transition of the Pt(1 1 0) surface above a critical coverage of NO(a), as evidenced by Rutherford backscattering (RBS), LEED and RHEED [17][18][19][20]. Coverage-dependent adsorption site switching was observed during NO adsorption: at low coverages bridge-bonded species are formed whereas on-top sites are preferred with the increasing coverage [11,18]. The NO site switching on Pt(1 1 0)-(1 · 2) was also verified by density functional theory (DFT) theoretical calculation [21].…”

“…NO can either donate electron density to the surface or accept electron density from the surface, whereas, for example, the empty 2p * orbital of CO can only accept electrons. Thus the chemistry of NO is much more complex than that of CO [1,11,12]. Related with platinum surface, Shimozu et al [13][14][15] systematically investigated adsorption and decomposition of NO on several Pt single crystal planes and observed that their abilities to decompose NO followed the order: Pt(4 1 0) > Pt(3 1 0) > Pt(1 0 0) > Pt(2 1 0) > Pt(1 1 0)-(1 · 2) % Pt(1 1 1).…”

Adsorption states of NO on the Pt(111) step surface

“…An absorption band of around 1750 cm −1 could be due to NO molecules at on-top sites of the step. In the previous IRAS studies of NO on Pt(110) [32,33], a broad peak at 1758 cm −1 was observed at high coverage and the peak at 1626 cm −1 decreased coincidentally. The 1626 cm −1 peak originates from bridge NO species on the Pt row of Pt(110).…”