Improvement of water resistance by Fe2O3/TiO2 photoelectrocatalysts for formaldehyde removal: experimental and theoretical investigation

Abstract

TiO2-based photocatalysts are a potential technology for removing indoor formaldehyde (CHOH) owing to their strong photooxidation ability. However, their photooxidation performance is generally weakened when suffering from the competitive adsorption of H2O. In a method inspired by the oxygen evolution reaction (OER) to generate intermediates with hydroxyl radicals on the anode electrode catalysts, an electric field was employed in this research and applied to the photooxidation of CHOH to prevent the competitive adsorption of H2O. Additionally, 0.5-5% Fe2O3 decorated TiO2 was employed to improve the photoelectrocatalytic activity. The influence of an electric field on hydroxyl-radical production was investigated by both density functional theory (DFT) with direct-imposed dipole momentum and photoelectrocatalytic experimental tests. The surface characterization of the photocatalysts, including transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and electron paramagnetic resonance (EPR), was conducted. DFT results show that a positive electric field with a strength of 0.05 Å/V was more favorable to produce hydroxyl on Fe2O3/TiO2(010) than was a negative electric field. Fe2O3 decoration can significantly boost hydroxyl formation, resulting from a decrease in the binding energy between the Fe of Fe2O3 and the oxygen and hydrogen atoms of H2O. The dissociated hydrogen atom of the H2O preferentially remained on the catalysts' surface rather than being released into the gas flow. The experimental results demonstrated that the application of a low-voltage of 150 V could not directly enhance the photooxidation of CHOH by either TiO2 or Fe2O3/TiO2 but that it could relieve the H2O inhibitory effect by more than 10% on the Fe2O3/TiO2.

Built-in electric fields and extra electric fields in the oxygen evolution reaction

“…Therefore, the key to addressing this issue is to activate H 2 O molecules and generate hydroxyl radicals, and the OER can produce hydroxyl radicals by extracting hydrogen atoms from H 2 O. 98 Dong 99 enhanced the decomposition of gaseous H 2 O using an extra electric field to generate hydroxyl radicals, thus substantially enhancing the removal of CHOH.…”

Understanding the prototype catalyst TiO2 surface with the help of density functional theory calculation

“…Although dimer adsorption is more favorable on anatase, monomer adsorption is more stable on Au/TiO 2 . Dong et al 163 demonstrated that a positive electric field with a strength of…”

“…Although dimer adsorption is more favorable on anatase, monomer adsorption is more stable on Au/TiO 2 . Dong et al 163 demonstrated that a positive electric field with a strength of 0.05 V/Å was preferable to a negative electric field for the production of hydroxyl on Fe 2 O 3 /TiO 2 (010). Fe 2 O 3 decoration can significantly boost hydroxyl formation, resulting from a decrease in the binding energy between the Fe and H 2 O. Non‐metallic materials can also be doped into TiO 2 surfaces and change the adsorption and dissociation characteristics of H 2 O.…”

Excellent room temperature catalytic activity for formaldehyde oxidation on a single-atom iron catalyst in a moist atmosphere

“…Compared with conventional catalysts, single-atom catalysts (SACs) exhibit many superior properties, including high catalytic activity, high adsorption selectivity and high metal atom utilization. 24 SACs show excellent performance in fuel cells, 25 electrocatalytic reduction of CO2, 26 and hydrogenolysis. 27 Similarly, SACs exhibit excellent properties in the field of catalytic oxidation: FeSA shows high catalytic activity for the catalysis of benzene, 28 methane, 29 and mercury 30 at room temperature.…”