Thermal Evolution and Instability of CO-Induced Platinum Clusters on the Pt(557) Surface at Ambient Pressure

Abstract

Carbon monoxide (CO) is one of the most-studied molecules among the many modern industrial chemical reactions available. Following the Langmuir-Hinshelwood mechanism, CO conversion starts with adsorption on a catalyst surface, which is a crucially important stage in the kinetics of the catalytic reaction. Stepped surfaces show enhanced catalytic activity because they, by nature, have dense active sites. Recently, it was found that surface-sensitive adsorption of CO is strongly related to surface restructuring via roughening of a stepped surface. In this scanning tunneling microscopy study, we observed the thermal evolution of surface restructuring on a representative stepped platinum catalyst, Pt(557). CO adsorption at 1.4 mbar CO causes the formation of a broken-step morphology, as well as CO-induced triangular Pt clusters that exhibit a reversible disordered-ordered transition. Thermal instability of the CO-induced platinum clusters on the stepped surface was observed, which is associated with the reorganization of the repulsive CO-CO interactions at elevated temperature.

Copper adparticle enabled selective electrosynthesis of n-propanol

“…In light of previous reports regarding the activation of metal surfaces by promoting surface cluster growth 25 – 28 , we hypothesized that the introduction of adparticles, surface clusters possessing a high population of low-coordinated surface sites, on pristine Cu surfaces could drive C 3 production by increasing both the adsorption of CO and the binding energy of *C 2 intermediates. Specifically, increased surface concentrations of CO and *C 2 would decrease the reaction energy requirement for generating C 3 product (i.e., n-propanol).…”

Surface science under reaction conditions: CO oxidation on Pt and Pd model catalysts

“…58 At pressures of around 1 hPa at RT, the Pt(755) surface forms an extended array of triangular clusters, 58 which become ordered at slightly elevated temperatures (350-360 K). 59 The CO-induced wandering of (100) steps and their doubling in height were confirmed by molecular dynamics (MD) simulations. 102 The MD simulations revealed another interesting property of the (100) steps of Pt(211), 2(111) Â (100).…”

“…These changes were explained as the possible formation of incommensurate structures or as CO bonded to Pt steps or kinks. Although CO seems to increase the mobility of Pt atoms at the step and induce the formation of kink sites, 55,58,59 large-scale roughening of the Pt (111) surface in CO was not observed at a pressure of around 100 kPa.…”

Adsorbate-driven reactive interfacial Pt-NiO 1− x nanostructure formation on the Pt 3 Ni(111) alloy surface

“…The corresponding oxygen-induced surface restructuring is strictly related to thermodynamic parameters (that is, pressure and temperature) such that the formation of oxidized Ni from Pt 3 Ni reliably follows the chemical potential of oxygen at a given temperature following this formula ( 17 ) This distinctive surface segregation phenomenon arises mainly from the adsorbate-dependent modification of the electronic structure of the surface, but the effect of the “pressure gap” also plays a critical role in metastable subsurface Ni atom segregation on the bimetallic Pt-Ni catalyst surface. The huge pressure gap between UHV and atmospheric pressure causes a large discrepancy in the chemical potential corresponding to approximately 0.3 eV ( 20 , 21 ). The exposed surface with a high coverage of molecular adsorbates results in restructuring behavior associated with a reduction of the surface free energy ( 22 – 24 ).…”