Studies of Ethylene Oxide Adsorption on Pt−Sn Alloys with TPD, HREELS, UPS, and DFT Calculations

Abstract

Ethylene oxide (EO) adsorption was studied on two ordered surface alloys: (2 × 2)-Sn/Pt(111) with θ Sn ) 0.25 ML, and ( 3 × 3)R30°-Sn/Pt(111) with θ Sn ) 0.33 ML. Nearly all EO desorbs molecularly during TPD in peaks at 198 K for the (2 × 2) alloy and 190 K for the ( 3 × 3)R30°alloy, corresponding to desorption activation energies of 12.1 and 11.6 kcal/mol, respectively. HREELS and UPS show that EO adsorbs molecularly even at low coverage through the oxygen atom with the molecular plane tilted away from the surface normal. DFT calculations provide details for the adsorption geometry: EO adsorbs without ring breaking, with oxygen bonding to Sn at a bond distance of 2.7-2.8 Å and a C-O-Sn bond angle of ∼120°. XPS indicates that the EO saturation coverage is not affected by the presence of Sn in the alloys and remains the same as for pure Pt(111) at 0.25 ML. A small amount (1-2%) of EO decomposition occurs during TPD for both alloy surfaces, and DFT calculations suggest that EO transforms into a more stable metallacycle configuration with oxygen bonding to Sn prior to decomposition. † Part of the "D. Wayne Goodman Festschrift".

CO tolerance of a Pt3Sn(111) catalyst in ethanol decomposition

“…As seen from Table 1, CH 3 CH 2 OH, CH 3 CH 2 O, CH 3 CHO and CH 2 O at the T Sn site are more stable than those at the T Pt site. That is, Sn plays a "bifunctional" role to strengthen the adsorption, providing good support to the experimental result on the Sn effect, 60,61 and bearing similarities to ethylene oxide 62 and cyclohexanone 63 adsorption on PtSn alloys.…”

Propane Dehydrogenation to Propylene and Propylene Adsorption on Ni and Ni‐Sn Catalysts

“…Similarly constructed periodic surfaces with similar computational settings were previously used successfully for studying adsorption and reactions on Ni [13] and other metal surfaces. [14][15][16][17][18][19][20][21][22][23] Adsorption energies were calculated at 0 K without zero-point energy corrections using as a reference the sum of energies for the corresponding clean surface and an isolated propylene molecule calculated separately. Adsorption energies are reported as positive numbers, À ΔE ads .…”

“…The remaining two bottom layers were constrained at the bulk Ni positions, accounting for the bulk structure. Similarly constructed periodic surfaces with similar computational settings were previously used successfully for studying adsorption and reactions on Ni [13] and other metal surfaces [14–23] …”

Spectroscopic observation and structure-insensitivity of hydroxyls on gold

“…Similar cluster and periodic structure models were previously successfully used to describe oxygen, H 2 O 2 and OOH adsorption on Au and other adsorbates on multiple surfaces. 9,13,15,18–28 The calculations show that on most Au surfaces hydroxyls preferentially adsorb on a bridge Au–Au site, with ν (O–H) being in a narrow range from 3683 to 3687 cm −1 (Fig. 2).…”