Pt–Ru model catalysts for anodic methanol oxidation: Influence of structure and composition on the reactivity

Spontaneous and Electrodeposition of Pt on Ru(0001)

“…6b) which is substantially higher than that found on a rough Pt(111) (≈ 1500 µA/cm 2 ) [25] and the Pt-Ru bulk alloy surface (≈ 900 µA/cm 2 ) [26] in a 0.05 M CH 3 OH solution [26]. The latter exhibits even much higher activity than Pt(111) with Ru islands grown at 300 K [27]. Similarly, the current density associated with HCOOH electrooxidation on Ru(0001) (60 µA/cm 2 ) is enhanced by a factor of about 100 with the Pt-modified electrode as reflected by Fig.…”

Epitaxial Growth of Ru and Pt on Pt(111) and Ru(0001), Respectively: A Combined AES and RHEED Study

“…As expected the Pt (111) cluster adopts favored the fcc bulk phase grown on Ru(0001) to minimize the surface strains. It is worthy to mention that the intermixing of Pt and Ru is difficult to detect by STM [21,23,27], since a clear assignment of a certain brightness in the STM image to either Pt or Ru is difficult, especially as the contrast found depends strongly on the status of the tunneling tip [21,42,43]. On the other hand, if the Pt-Ru alloy were formed after the Pt deposition on Ru(0001), the additional reflections due to the alloy would appear in the RHEED patterns, like that known for the Hg-Pt alloy formation on Pt(111) by Hg electrodeposition at room temperature [44].…”

“…The corresponding AES spectrum in Figure 5(c) shows that the Auger Ru-signal increases significantly, in line with the RHEED observations ( Figures 4(f) and 4(g)), whereby the pronounced Ru reflections develop. On the other hand, the Ru deposited on Pt(111) prepared by Ru vapor deposition in UHV shows 3D-islands having a width of 5-10 nm and multilayer thick by STM [27]. The difference in the size distribution of the clusters from that obtained by electrodeposition (∼2 nm) is apparently due to the evaporation rate of Ru in UHV and the subsequent annealing at 800 K. The subsequent annealing to 800 K leads to these islands to collapse and induces a ripening process, resulting in large, multilayer islands [27].…”

“…On the other hand, the Ru deposited on Pt(111) prepared by Ru vapor deposition in UHV shows 3D-islands having a width of 5-10 nm and multilayer thick by STM [27]. The difference in the size distribution of the clusters from that obtained by electrodeposition (∼2 nm) is apparently due to the evaporation rate of Ru in UHV and the subsequent annealing at 800 K. The subsequent annealing to 800 K leads to these islands to collapse and induces a ripening process, resulting in large, multilayer islands [27]. We are questioning whether the 3D-spots in the RHEED (Figure 4(f)) are due to the Pt or Ru nanoclusters.…”

“…Vapor deposition of about 1 ML ruthenium onto a clean Pt(111) surface and subsequent short annealing to 820 K leads to the formation of 3D-islands having a width of 5-10 nm [27]. Furthermore, the lattice strain of an admetal layer with the underlying substrate may result from their lattice mismatch, like that found for Pt on Ru(10-10) [16], Co on Pt(111) [28], Ag on Pt(111) [29], and Cu on Ru(0001) [30]; it is expected to gradually vanish for two, three, or more layers, leading to lattice dislocations as observed for Pt overlayer on Ru(0001) [4,23] and Ru on Pt(111) observed in the present work.…”