Kinetics of the nitric oxide + carbon monoxide reaction on clean platinum: steady-state rates

The stability and electronic properties of Pt-modified Cu(1 1 0) and Cu(1 1 1) in the absence/presence of small molecules: a density-functional theory modeling

Pt-Cu bimetallic alloys, as a key component in many heterogeneous catalysts, have the potential to be used in a range of industrially important reactions. The stability of platinum-modified Cu(1 1 0) and Cu(1 1 1) surfaces in the absence/presence of CO, NO and O has been investigated based on density-functional theory. We find that Pt alloyed in the second layer of the Cu (1 1 0) surface, rather than in the bulk, is the most favorable configuration. To relieve the strain, platinum tends to stay in the surface layer of close-packed Cu(1 1 1). Adsorbates can affect the stability of Pt-modified surfaces. Upon the adsorption of CO and NO, Pt segregation to the (1 1 0) surface becomes favorable, while on oxygen adsorption, no segregation occurs. Platinum only prefers to segregate on the Cu (1 1 1) surface when it is exposed to carbon monoxide, it tends to locate in the second layer for the other two adsorbates. Combining the position of d-band center, the d-bandwidth, and the separation between the bonding and antibonding states of the adsorbates, we interpret the results and correlate the relationship between the electronic properties of the substrate and the adsorption energy of the adsorbates, which could shed light on the prediction of bimetallic structures with desirable chemical properties.

NO Reduction by CO Catalyzed with Au/TiO2 in Oxygen-rich Condition

Gold nanoparticles supported on titania catalysts with different Au loadings were prepared and evaluated in the reaction of NO reduction by CO in an oxygen rich condition. The crystalline structures of the Au/TiO2 materials were refined with Rietveld method. TiO2 support chiefly contains anatase phase, having a crystalline size ranged from 5 to 15 nm. Au particles have an average crystal size approximately 2-5 nm as Au concentration less 3 wt %. In the reaction of NO + CO + O2, the Au/TiO2catalysts show a selectivity to 100 % N2, neither NO2 nor N2O was yielded in the reaction temperature between 25 and 400 °C, which strongly indicates that Au/TiO2catalysts are much superior to the other catalysts like Pt/TiO2 catalysts on which N2O was usually produced in the reaction temperature below 200 °C and NO2 was produced in the reaction temperature above 300 °C under a similar reaction condition.