Insight into Low-Temperature Styrene Oxidation over Nano CeO₂ Catalysts: Modulating Ce–O Bond Strength to Construct Oxygen Defect Engineering

Abstract

It has been widely accepted that oxygen vacancies are critical to catalytic oxidation activities. However, the effects of Ce–O bond strength on the formation of oxygen vacancies and the oxidation rate of styrene remain ambiguous. Herein, a series of CeO2 (CeO2-100, CeO2-140, CeO2-180) were synthesized to uncover the effects of Ce–O bond strength on surface chemical properties and unravel the oxidation mechanism of styrene via comprehensive characterization techniques and theoretical calculations. DFT calculations showed a positive correlation between the Ce–O bond strength and the formation of oxygen vacancies. The CeO2-100 catalyst exhibited a lower styrene degradation temperature (T 100 = 223 °C) and the lowest apparent activation energy (E a = 19.12 kJ/mol). This is due to the fact that weakening the Ce–O bond strength would make it easier to generate oxygen vacancies. More oxygen vacancies facilitate the adsorption of styrene and the formation of surface adsorbed oxygen, thereby accelerating styrene oxidation. In situ DRIFTS demonstrated that more oxygen vacancies can accelerate the oxidation of important intermediate products and further promote the deep oxidation of styrene to CO2 and H2O. Furthermore, the CeO2-100 catalyst showed better activity stability at 223 °C and good water resistance in the presence of 10 vol % water.

A [Cu2O2]2+ Core in Cu/ZSM-5 for Efficient Selective Catalytic Oxidation of Nitrogen-Containing VOCs and NH3

“…Volatile organic compounds (VOCs) are the main precursors of ozone and photochemical smog, seriously harmful to the environment and human health, attracting much public attention. − Nitrogen-containing VOCs (NVOCs) such as amides, nitrile, amines, and nitro-compounds, which originate primarily from industrial processes and motor vehicles under low-speed driving, are often foul-smelling and highly toxic and are more harmful than conventional VOCs. − So far, various methods have been developed for NVOC removal, such as absorption, thermal combustion, and catalytic oxidation. With advantages in purification efficiency and cost, catalytic oxidation is one of the most promising methods. ,− Different from other VOCs oxidation, the N 2 selectivity during selective catalytic oxidation (SCO) of NVOCs must be considered as an important target to avoid the secondary pollution of NO x . − Therefore, the cooperative control of VOCs and NO x is the key issue in eliminating NVOCs.…”

Defect Engineering of MOF-Derived Carbon for Peroxymonosulfate Activation to Degrade Sulfadiazine: Roles of Carbon Vacancies and Edge Defects

“…Luo et al demonstrated that doping nitrogen can synthesize defect-rich carbon materials to effectively degrade rhodamine B . In addition, the removal of heteroatoms predominantly relies on pyrolysis processes because heteroatom groups can decompose at high pyrolysis temperatures, thereby removing the carbon atoms bonded to them, or the rearrangement of the carbon lattice after the removal of heteroatoms will lead to the increase of defects. − In contrast, the approach of removing heteroatoms to induce defects is simpler and more effective . Nevertheless, to achieve a high level of defects, carbon materials need to have a high content of heteroatoms, which is not satisfied by common carbon materials .…”