Adsorption and gas-sensing characteristics of a stoichiometric alpha-Fe2O3 (001) nano thin film for carbon dioxide and carbon monoxide with and without pre-adsorbed O-2
Journal
Rsc Advances
Journal Volume
6
Journal Issue
5
Pages
3514-3525
Date Issued
2016
Author(s)
Abstract
Herein, for the first time, the adsorption and gas-sensing characteristics of the CO2 and CO molecules on a stoichiometric α-Fe2O3 (0 0 1) nano thin film with and without pre-adsorbed O2 molecules have been studied using the density functional theory (DFT) method. Without pre-adsorbed O2 molecules, the CO2 molecule plays the role of an acceptor and obtains electrons from the stoichiometric α-Fe2O3 (0 0 1) nano thin film. For the O2 pre-adsorption α-Fe2O3 (0 0 1) nano thin film system, the CO2 molecule also plays the role of an acceptor. However, less number of electrons are transferred to the CO2 molecule as compared to the pre-adsorbed O2 molecules. Different from the CO2 molecule, the CO molecule always plays the role of a donor for the α-Fe2O3 (0 0 1) nano thin film system with and without pre-adsorbed O2. The theoretical results verify that the CO molecule can react with the lattice oxygen or adsorbed oxygen of the α-Fe2O3 (0 0 1) nano thin film. The electrons transferred to the stoichiometric α-Fe2O3 (0 0 1) nano thin film from the CO molecule or newly formed CO2 molecule are more than that transferred to the O2 pre-adsorption α-Fe2O3 (0 0 1) nano thin film. For the stoichiometric or O2 pre-adsorption α-Fe2O3 (0 0 1) nano thin film, the CO2 and CO molecules exhibited opposite behaviors of charge transformation. In addition, pre-adsorbed O2 molecules displayed competitive adsorption with the CO2 or CO molecule. The pre-adsorbed O2 molecules hinder electron transfer to the CO2 molecules from the α-Fe2O3 (0 0 1) nano thin film or hinder electron transfer to the α-Fe2O3 (0 0 1) nano thin film from the CO molecule. Theoretical results demonstrate that the surface of α-Fe2O3 materials (0 0 1) could be prepared for use as adsorbents or gas sensors for CO2 and CO molecules. Their structures are stable after CO2 molecules are adsorbed or after the reaction of CO molecules with the lattice oxygen or adsorbed oxygen of the α-Fe2O3 (0 0 1) nano thin film.
Type
journal article