Dynamics of CO Oxidation on a Polycrystalline Platinum Electrode: A Time-Resolved Infrared Study

We perform dynamic Monte Carlo simulations to understand the kinetics of CO oxidation on Pt surface. Our simulations are performed on a model for CO electro-oxidation, where oxygen-containing species (adsorbed OH) formed on the Pt surface reacts with adsorbed CO by a Langmuir–Hinshelwood mechanism to form CO2. A systematic study of the model parameters shows that we obtain better electrocatalytic activity by increasing the surface diffusion coefficient of CO (kD) or the rate of reaction between adsorbed CO and adsorbed OH. We also show that if the initial state of adsorbed CO is a closely packed structure, increasing the surface coverage can result in negative voltammetry peak shifts because of the formation of weakly adsorbed states of CO. We have also modeled bulk CO voltammetry by introducing a CO adsorption rate, k4. We show that near-zero currents are obtained for the potentials (E) where the rate of OH adsorption, k1(E), is much smaller than k4. We also note that kD plays no significant role in CO oxidation when kD≪k4. Our results also show that bulk CO voltammetry peaks shift to more positive potentials compared to the stripping, as observed in experiments. Our potential step simulations show no difference in bulk and stripping current transients in the potential regions where k1(E)≫k4, whereas they vary significantly when k4≅k1(E).

Lateral modification and organization of mixed adlattices on polycrystalline platinum electrodes

CO adsorption and oxidation on a Pt(111) electrode modified by ruthenium deposition: an IR spectroscopic study

Dynamics of the CO oxidation NO reduction reaction on thin MgO (100) supported Pd clusters has been studied by quantum chemical molecular dynamics (QCMD). Chemical changes, change of adsorption states, and structural changes were investigated. We observed that CO adsorption occurs molecularly, whereas NO adsorption occurs first molecularly on the Pd cluster, but it is then dissociatively adsorbed on Pd cluster after interacting with CO. Oxygen atoms resulting from the NO dissociation react with adsorbed CO and form CO2 that desorbs from the Pd cluster, whereas the remaining N atom diffuses in the lattice of the Pd cluster. NO dissociation has been found to be the key step for this reaction. Furthermore, from the molecular dynamics and electronic structure calculations, we have identified a number of consequences for the interpretation and modeling of diffusion experiments demonstrating the coverage. As far we know, this is the first QCMD based simulation of the dynamics of CO oxidation, NO reduction, and ...

The Dynamics of Oxygen Storage in Ceria–Zirconia Model Catalysts Measured by CO Oxidation under Stationary and Cycling Feedstream Compositions

The dynamics of surface chemical reactions: infrared chemiluminescence of the product CO 2 desorbed from metal surfaces

The dynamics of CO oxidation on Pt deduced from translational, rotational and vibrational excitation in product CO 2

Functionalization of carbon support and its influence on the electrocatalytic behaviour of Pt/C in H 2 and CO electrooxidation

Gold nanoparticles of ca. 4 nm in diameter were deposited on a Pt−Ru/C catalyst by the gas-phase grafting method, and the electrocatalytic activities of Pt−Ru/C and gold nanoparticles deposited on a Pt−Ru/C catalyst in the electrooxidation of methanol and CO were studied. The deposition of gold nanoparticles on Pt−Ru/C enhanced its electrocatalytic activity for methanol oxidation at a lower potential region (<450 mV). In addition, the promotion of CO oxidation by gold nanoparticles on Pt−Ru/C was confirmed by CO stripping voltammetry.

Ultrafast electron transfer (ET) processes are important primary steps in natural and artificial photosynthesis, as well as in molecular electronic/photonic devices. In biological systems, ET often occurs surprisingly fast over long distances of several tens of angströms. Laser-pulse irradiation is conveniently used to generate strongly oxidizing (or reducing) excited states whose reactions are then studied by time-resolved spectroscopic techniques. While photoluminescence decay and UV-vis absorption supply precise kinetics data, time-resolved infrared absorption (TRIR) and Raman-based spectroscopies have the advantage of providing additional structural information and monitoring vibrational energy flows and dissipation, as well as medium relaxation, that accompany ultrafast ET. We will discuss three cases of photoinduced ET involving the Re(I)(CO)3(N,N) moiety (N,N = polypyridine) that occur much faster than would be expected from ET theories. [Re(4-N-methylpyridinium-pyridine)(CO)3(N,N)](2+) represents a case of excited-state picosecond ET between two different ligands that remains ultrafast even in slow-relaxing solvents, beating the adiabatic limit. This is caused by vibrational/solvational excitation of the precursor state and participation of high-frequency quantum modes in barrier crossing. The case of Re-tryptophan assemblies demonstrates that excited-state Trp → *Re(II) ET is accelerated from nanoseconds to picoseconds when the Re(I)(CO)3(N,N) chromophore is appended to a protein, close to a tryptophan residue. TRIR in combination with DFT calculations and structural studies reveals an interaction between the N,N ligand and the tryptophan indole. It results in partial electronic delocalization in the precursor excited state and likely contributes to the ultrafast ET rate. Long-lived vibrational/solvational excitation of the protein Re(I)(CO)3(N,N)···Trp moiety, documented by dynamic IR band shifts, could be another accelerating factor. The last discussed process, back-ET in a porphyrin-Re(I)(CO)3(N,N) dyad, demonstrates that formation of a hot product accelerates highly exergonic ET in the Marcus inverted region. Overall, it follows that ET can be accelerated by enhancing the electronic interaction and by vibrational excitation of the reacting system and its medium, stressing the importance of quantum nuclear dynamics in ET reactivity. These effects are experimentally accessible by time-resolved vibrational spectroscopies (IR, Raman) in combination with quantum chemical calculations. It is suggested that structural dynamics play different mechanistic roles in light-triggered ET involving electronically excited donors or acceptors than in ground-state processes. While TRIR spectroscopy is well suitable to elucidate ET processes on a molecular-level, transient 2D-IR techniques combining optical and two IR (or terahertz) laser pulses present future opportunities for investigating, driving, and controlling ET.

The co-catalytic effect of Sn, Ru and Mo decorating steps of Pt(111) vicinal electrode surfaces on the oxidation of CO

Femtosecond X-ray laser pulses synchronized with an optical laser were employed to investigate the reaction dynamics of the photooxidation of CO on the anatase TiO2(101) surface in real time. Our time-resolved soft X-ray photoemission spectroscopy results provide evidence of ultrafast timescales and, coupled with theoretical calculations, clarify the mechanism of oxygen activation that is crucial to unraveling the underlying processes for a range of photocatalytic reactions relevant to air purification and self-cleaning surfaces. The reaction takes place between 1.2 and 2.8 (±0.2) ps after irradiation with an ultrashort laser pulse leading to the formation of CO2, prior to which no intermediate species were observed on a picosecond time scale. Our theoretical calculations predict that the presence of intragap unoccupied O2 levels leads to the formation of a charge-transfer complex. This allows the reaction to be initiated following laser illumination at a photon energy of 1.6 eV (770 nm), taking place via a proposed mechanism involving the direct transfer of electrons from TiO2 to physisorbed O2.

Dynamics of CO oxidation: A model with two oxygen forms

Characterization and Fourier transform infrared studies of the effects of TiO 2 crystal phases during CO oxidation on [formula omitted] catalysts

The electrooxidation of carbon monoxide on ruthenium modified Pt(110)