Hydroxylation of ZnO/Cu(1 1 1) inverse catalysts under ambient water vapor and the water–gas shift reaction

Abstract

The interaction of water vapor with ZnO/CuO x /Cu(1 1 1) surfaces was investigated using synchrotron-based ambient pressure x-ray photoelectron spectroscopy (AP-XPS) and densityfunctional theory (DFT) calculations. Cu(1 1 1) does not dissociate the water molecule.Cleavage of O-H bonds was seen with AP-XPS after depositing ZnO or preparing CuO x on the copper substrate. The results of DFT calculations show unique behavior for ZnO/CuO x / Cu(1 1 1), not seen on Cu(1 1 1), CuO x /Cu(1 1 1) or ZnO(0 0 01). The ZnO/CuO x /Cu(1 1 1) system binds water quite well and exhibits the lowest energy barrier for O-H bond cleavage. The presence of unsaturated Zn cations in the islands of ZnO led to high chemical reactivity. In order to remove the OH from ZnO/CuO x /Cu(1 1 1) and ZnO/Cu(1 1 1) surfaces, heating to elevated temperatures was necessary. At 500-600 K, a significant coverage of OH groups was still present on the surfaces and did react with CO during the water-gas shift (WGS) process. The final state of the sample depended strongly on the amount of ZnO present on the catalyst surface. For surfaces with a ZnO coverage below 0.3 ML, the adsorption of water did not change the integrity of the ZnO islands. On the other hand, for surfaces with a ZnO coverage above 0.3 ML, a ZnO → Zn x OH transformation was observed. This transformation led to a decrease in the WGS catalytic activity.

In Situ Studies of Methanol Decomposition Over Cu(111) and Cu2O/Cu(111): Effects of Reactant Pressure, Surface Morphology, and Hot Spots of Active Sites

“…The CH 3 OH decomposition on Cu(111) preferred to start with the cleavage of the O–H bond, followed by the conversion of *CH 3 O to *CH 2 O and its desorption as CH 2 O gas. , It rendered CH 2 O instead of CO as the likely product of CH 3 OH decomposition on Cu(111) . In the present DFT calculations, CH 3 OH dissociation was also studied on a Cu 2 O/Cu­(111) model, Figure S1, which has previously demonstrated its useful application as an excellent support in various catalytic processes, such as the water gas shift reaction, , CO oxidation, , methane conversions, , and CO 2 hydrogenations …”

“…76,78 It rendered CH 2 O instead of CO as the likely product of CH 3 OH decomposition on Cu (111). 78 In the present DFT calculations, CH 3 OH dissociation was also studied on a Cu 2 O/Cu(111) model, Figure S1, which has previously demonstrated its useful application as an excellent support in various catalytic processes, such as the water gas shift reaction, 111,112 CO oxidation, 69,113 methane conversions, 39,40 and CO 2 hydrogenations. 114 On the Cu 8) as that seen for Cu(111), 75,76,78 and the O−H bond length in CH 3 OH was slightly stretched from 0.956 Å in gas phase, to 0.982 Å.…”

Understanding Methanol Synthesis on Inverse ZnO/CuOx/Cu Catalysts: Stability of CH3O Species and Dynamic Nature of the Surface

“…Figure compares the C 1s XPS spectra collected at 300 K while exposing the plain Cu 2 O/Cu­(111) and ZnO/Cu 2 O/Cu­(111) surfaces with 0.1 and 0.4 ML of zinc oxide to 10 mTorr of methanol. The C 1s adsorption features were assigned following previous XPS studies. ,,,, …”

“…This type of basic information is necessary to optimize the performance of catalysts utilized to facilitate the CO 2 → CH 3 OH transformation. The chemical reactivity of methanol, as the simplest carbon-containing alcohol, has garnered considerable attention related to the transformation of C–H and C–OH bonds on surfaces of metals, − oxides, − and mixed oxides or more complex materials. − In this work, we study the dynamic interaction of methanol with ZnO/Cu 2 O/Cu­(111) catalysts employing ambient pressure X-ray photoelectron spectroscopy (AP-XPS), scanning tunneling microscopy (STM), and calculations based on density functional theory (DFT). Preferential adsorption is observed on the ZnO regions of the catalysts, with the adsorbate undergoing desorption as CH 3 OH or full decomposition (CH 3 O → CH 2 O → CHO → CO).…”

Synergy between a Silver–Copper Surface Alloy Composition and Carbon Dioxide Adsorption and Activation

“…However, the current AgCu system differs from the extensively reported metal-metal oxide systems. [25][26][27][28][29][30][31] The bimetallic surface exhibits a synergetic effect between the Ag and Cu surface composition that tunes the CO2 (H2O)-AgCu interactions, initiating surface reconstruction, and altering the CO2 activation process. Thus, CO2 adsorption and activation on AgCu surfaces operates entirely differently compared to pure Ag or Cu surface, providing possibilities for further tuning CO2 adsorption behavior to facilitate selective product formation.…”