Probing the Effect of Surface Strain on CO Binding to Pd Thin Films

Abstract

We report measurements to investigate the effects of mechanical strain on the binding energy of carbon monoxide (CO) on the (111) surface of a 16 nm thin film of palladium (Pd) grown on rutile titanium dioxide (r-TiO2). The lattice mismatch between Pd and the r-TiO2 leads to a tensile mechanical in-plane stress in the Pd layer of approximately 0.38 GPa. We observe an increase of (40 ± 10) kJ mol–1 in the CO binding energy for the 16 nm sample compared to a bulk Pd(111) crystal, which is in qualitative agreement with expectations based on the d-band model.

Au-Stabilized Nanoporous PdCuAu Alloys Exhibiting Outstanding Catalytic Activity and Durability for the Formic Acid Oxidation Reaction

“…Therefore, the CO resistance improves in the order from NPG-Pd, NPG-PdCu, Pd/C to NPG-PdCuAu as indicated in Figure 3a. Previous literature reported that compressing the lattice of Pd could weaken the binding energy of Pd−CO and Cu could provide hydroxyl groups at low potentials to remove the surface-adsorbed CO. 10,[15][16][17]34 Integrating with the XRD patterns in Figure 2a, NPG-PdCu with a smaller lattice parameter and a higher initial Cu proportion should exhibit a better CO resistance than NPG-PdCuAu which is obviously different from the data in Figure 3a. To explore the reasons for this apparent anomaly, surface compositions of NPG-PdCu and NPG-PdCuAu electrodes were separately detected during the conventional potential cycling experiments for stable surface structures before electrochemical measurements.…”

Application of an Event-Based Camera for Real-Time Velocity Resolved Kinetics

“…The apparatus used in this work is similar to that used in earlier VRK experiments. − , It consists of a source chamber equipped with both a Parker Series 9 General Valve and an Even-Lavie type nozzle, producing two pulsed molecular beams. Both beams are skimmed and pass two stages of differential pumping before entering an ultrahigh vacuum chamber with a base pressure of 6 × 10 –10 mbar where a Pt(332) sample is held.…”

“…For surface kinetics experiments, the clean and reconstructed sample is then transported in front of the molecular beam behind an ion imaging detector similar to those described previously. − , Molecules leaving the surface are ionized at a distance of about 10 mm from the surface via nonresonant multiphoton ionization using 800 nm pulses from a Ti:Sa laser (120 fs, 1 kHz, 450 μJ per pulse) focused with a 150 mm plano-convex lens. The ions are generated between a repeller and an extractor grid, both with a diameter of 41 mm and separated from one another by 5 mm.…”

Strain and stress effects on single crystal-supported titania and related nanostructures

“…Apart from the strain that arises from the vertical misfit of Pd (111) on rutile TiO 2 (110), there is also an influence from the lateral misfit. Harding et al [39] used XRD to measure the out-of-plane lattice parameter of a 164 Å thick Pd (111) film also grown on rutile TiO 2 (110). From that, the in-plane strain and stress were computed.…”

“…The study of metals supported on oxides such as TiO 2 have been extensively studied due the importance of such systems in catalysis [36,37]. Recent studies show that the TiO 2 substrate can impart strain onto the supported nanoparticles, changing their reactivity to CO molecules [38,39]. Strain can also be introduced into a material by implanting objects beneath the surface.…”