Guaiacol Adsorption and Decomposition on Platinum

Abstract

Guaiacol (2-methoxyphenol, C6H4(OH)­(OCH3)) adsorption and reactions on a Pt(100) surface were studied with infrared reflection–absorption spectroscopy (IRAS) and temperature programmed desorption (TPD) measurements at different surface coverage values from 100 to 800 K. In addition, density functional theory (DFT) calculations were used to determine geometries, adsorption energies, and vibrational frequencies for adsorption structures. Depending on surface coverage, guaiacol formed one or two physisorbed states. At low coverage, a single state with a desorption peak at 225 K was observed. At high coverage, two physisorbed states were observed with desorption peaks at 195 and 225 K. At temperatures above 225 K, after the desorption of physisorbed layers, a dissociatively adsorbed structure, C6H4O­(OCH3) + H, was observed. Recombinative molecular guaiacol desorption was detected at 320 K. The dissociatively adsorbed structure was stable up to 337 K when C–O bonds began to break. Molecularly adsorbed guaiacol in horizontal (flat-lying) configurations bound through its benzene ring was not observed under all tested conditions. Similarities of vibrational spectra and desorption measurements for a Pt(100) surface in this study and a Pt(111) surface reported previously demonstrate that the obtained results are generally valid for low-index Pt crystal planes and, more importantly, for catalytic Pt nanoparticles.

Development of a New Route for Separating and Purifying 4-Ethyl-2-methoxyphenol Based on the Reaction Mechanism between the Chemical and Calcium Ion

“…As shown in Figure 4 a, the hydroxyl absorption band of EMP in the first stage δ (C–OH) was located at 1366.73 cm –1 , while it disappeared in the spectra of EMP-Na and Prod-S1. 28 It indicated that a neutralization reaction occurred in the first stage. To further illustrate the occurrence of the acid–base reaction, the infrared spectra of EMP, Prod-S1, and EMP-Na were further compared in Figure 4 a.…”

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] …”

Band gap of reduced graphene oxide tuned by controlling functional groups

“…The density of states was calculated with 1 empty band and a k-point grid of 2 Â 2 Â 1.The computational settings were similar to those that were previously used successfully to describe molecular properties of surface functional groups, including hydroxyls. [54][55][56][57][58] The rGO structure was modeled as an infinite slab constructed using a periodic unit cell. Edge sites were not considered in the model because they represented less than 0.2% of all carbon atoms due to the large size of our rGO sheets (300-800 nm).…”