Novel Insight in the CO Oxidation on RuO₂(110) by in Situ Reflection−Absorption Infrared Spectroscopy

Abstract

In situ reflection-absorption infrared spectroscopy (RAIRS) experiments identify the most abundant surface species during the CO oxidation on RuO 2 (110) in a wide pressure range from 10 -7 mbar to 10 -3 mbar. Under reaction conditions with highest catalytic activity most of the undercoordinated (bridging) surface O atoms of the RuO 2 (110) surface are shown to be replaced by bridging CO molecules, thereby modifying the operating catalyst. The observed replacement of bridging O by bridging CO contradicts recently published ab initio kinetic Monte Carlo (k-MC) simulations on the same catalytic system. The C-O stretching frequency depends not only on the adsorption site but also on the local adsorption environment on the surface. This allows us to gain unprecedented information about the distribution and local configuration of the adsorbed reactants on the catalyst's surface during the CO oxidation reaction, which may serve as benchmarks for future k-MC simulations. Under reaction conditions the catalyst surface exposes areas which are catalytically active and areas which are poisoned by densely packed bridging CO and on-top CO. The actual reaction proceeds via the so-called Langmuir-Hinshelwood mechanism in that neighboring on-top O and on-top CO preferentially recombine to form CO 2 . The thermally induced restoration of the mildly reduced RuO 2 (110) surface was studied in situ on the atomic scale.

“First‐Principles” kinetic monte carlo simulations revisited: CO oxidation over RuO2(110)

“…In the same paper, where also the TOF as a function of the reactant feed ratio was published and to which Reuter and Scheffler have compared their simulated TOF values, ex situ HREELS[15] indicates that virtually all bridging O had been replaced by CO molecules after reaction with an optimum reactant feed. In the meantime, in situ RAIRS data under the same experimental conditions ( p (CO) = 2 × 10 −7 mbar and p (O 2 ) = 10 −7 mbar at T = 350 K) have been collected,[34] confirming this conclusion. The RAIRS experiments are easily reconciled with the kMC simulations based on the Kiejna and Seitsonen sets, but not with those based on the Reuter set.…”

“…Instead of the simple kinetic reaction data, the configuration of reactants on the catalyst's surface will serve more rigorously as a benchmark when comparing kMC results to experiment. Among the surface sensitive techniques RAIRS,[34] STM,[43] HP‐XPS,[44] and some other, spectroscopic techniques are able to provide this kind of information.…”

Hydrogen-Promoted Chlorination of RuO2(110)

“…Exposing the surface to CO at 420 K leads to the production of CO 2 (gas) by recombination of on top CO ot with bridging O br and to a concomitant occupation of the bridge sites by CO (CO br ) 23 …”

Insight into the Mechanism of CO Oxidation on WO3(001) Surfaces for Gas Sensing: A DFT Study

“…More than 80% of the CO in the atmosphere comes from the imperfect combustion of carbonaceous materials and vehicle exhaust. With the development of the urban environment and increased auto use, it is necessary to detect the amount of CO to control the air quality, and the development of CO sensing materials has become an important subject of current research [ 6 , 7 , 8 , 9 , 10 , 11 , 12 ]. Owing to their advantages of wide detection range, good stability, long lifetime and rapid response, metal oxides are absolutely competitive candidate materials for CO detection [ 13 , 14 , 15 ].…”