CO adsorption on Pt (111) and Pd (111) surfaces: A first-principles based lattice gas Monte-Carlo study

Ambient Temperature CO Oxidation Using Palladium–Platinum Bimetallic Catalysts Supported on Tin Oxide/Alumina

A series of Pt-based catalysts were synthesised and investigated for ambient temperature CO oxidation with the aim to increase catalytic activity and improve moisture resistance through support modification. Initially, bimetallic PtPd catalysts supported on alumina were found to exhibit superior catalytic activity compared with their monometallic counterparts for the reaction. Following an investigation into the effect of Pt/Pd ratio, a composition of 0.1% Pt/0.4% Pd was selected for further studies. Following this, SnO2/Al2O3 supports were synthesised from a variety of tin oxide sources. Catalytic activity was improved using sodium stannate and tin oxalate precursors compared with a traditional tin oxide slurry. Catalytic activity versus tin concentration was found to vary significantly across the three precursors, which was subsequently investigated by X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDX).

Challenges and breakthroughs in post-combustion catalysis: how to match future stringent regulations

This short overview briefly summarizes the prominent evolutions and scientific breakthroughs in the development of end-of-pipe technologies with respect to the standard regulations of atmospheric pollutant emissions from automotive exhaust.

Thermodynamics of the one-dimensional parallel Kawasaki model: exact solution and mean-field approximations

The adsorption isotherm for the recently proposed parallel Kawasaki (PK) lattice-gas model [Phys. Rev. E 88, 062144 (2013)] is calculated exactly in one dimension. To do so, a third-order difference equation for the grand-canonical partition function is derived and solved analytically. In the present version of the PK model, the attraction and repulsion effects between two neighboring particles and between a particle and a neighboring empty site are ruled, respectively, by the dimensionless parameters ϕ and θ. We discuss the inflections induced in the isotherms by situations of high repulsion, the role played by finite lattice sizes in the emergence of substeps, and the adequacy of the two most widely used mean-field approximations in lattice gases, namely, the Bragg-Williams and the Bethe-Peierls approximations.

Kinetically limited CO adsorption: spill-over as a highly effective adsorption pathway on bimetallic surfaces

We demonstrate that the (local) adsorbed carbon monoxide, COad , coverage on the Pt-free areas of bimetallic Pt/Ru(0001) surfaces (a Ru(0001) substrate partly covered by Pt monolayer islands) can be increased to ∼0.80 monolayers (ML), well above the established saturation COad coverage of 0.68 ML, even under ultrahigh vacuum conditions by using spill-over of CO adsorbed on the Pt islands to the Ru areas as an highly effective adsorption channel. The apparent COad saturation coverage of 0.68 ML on pure Ru(0001) is identified as due to kinetic limitations, hindering further uptake from the gas phase, rather than being caused by thermodynamic reasons. This spill-over mechanism is proposed to be a general phenomenon for adsorption on bimetallic surfaces.

Tunable Pt nanocatalysts for the aerobic selox of cinnamyl alcohol

The selective aerobic oxidation of cinnamyl alcohol over Pt nanoparticles has been tuned via the use of mesoporous silica supports to control their dispersion and oxidation state. High area two-dimensional SBA-15, and three-dimensional, interconnected KIT-6 silica significantly enhance Pt dispersion, and thus surface PtO2 concentration, over that achievable via commercial low surface area silica. Selective oxidation activity scales with Pt dispersion in the order KIT-6 ≥ SBA-15 > SiO2, evidencing surface PtO2 as the active site for cinnamyl alcohol selox to cinnamaldehyde. Kinetic mapping has quantified key reaction pathways, and the importance of high O2 partial pressures for cinnamaldehyde production.