Novel Core–Shell (ε-MnO₂/CeO₂)@CeO₂ Composite Catalyst with a Synergistic Effect for Efficient Formaldehyde Oxidation

Abstract

A novel core–shell (ε-MnO2/CeO2)@CeO2 composite catalyst with a synergistic effect was prepared by hydrothermal reaction and thermal decomposition and its application to high-efficiency oxidation removal of formaldehyde (HCHO) was systemically investigated. The (MnCO3/CeO2)@CeO2 precursor was prepared first by the one-pot hydrothermal reaction of Mn2+ and Ce3+ solutions with a CO2-storage material (CO2SM) without any external templates or surfactants required. The thermal decomposition of the precursor afforded the core–shell (ε-MnO2/CeO2)@CeO2 composite catalyst with excellent catalytic performance. HCHO in the feed gas (180 ppm HCHO, 21% O2, N2 balanced) at a gas hourly space velocity of 100 L/(gcat h) is 100% converted over the catalyst at 80 °C. The conversion rate remains above 95% in 72 h and above 73.8% in 140 h, suggesting the strong stability of the catalyst at high gas flow rates and relatively low temperatures. The synergistic mechanism of the catalyst was explored by X-ray diffraction, Raman, Brunauer–Emmett–Teller, transmission electron microscopy, and X-ray photoelectron spectroscopy. The number of defects in the catalyst and the strength of the Mn–O bond in ε-MnO2 can be tuned by adjusting the synthesis conditions. More oxygen vacancies on the surface of CeO2 can make the synergistic effect of the catalyst stronger, which significantly improves the lattice oxygen (Olatt) activity on the surface of ε-MnO2. Our work has provided new insights into the preparation of the desired composite catalysts with excellent performances.

Interfacial effects in CuO/Co3O4 heterostructures enhance benzene catalytic oxidation performance

“…Typically, plenty of adsorbed O 2 species on the surface of the catalyst is the prerequisite factor for the occurrence of catalytic oxidation because of its association with the capture of organic molecules and the activation of gaseous oxygen. [83][84][85] The high-resolution XPS spectra of Co 2p and Cu 2p are shown in Fig. 5b and c.…”

Identifying the Fe3Mn3O8 phase as a superior catalyst for low-temperature catalytic oxidation of formaldehyde in air

“…At 25 °C, the removal efficiency of Fe-Mn (1 : 1) could reach 83% at the GHSV of 300 L g −1 h −1 , 75% at 600 L g −1 h −1 , and even 42% at 1200 L g −1 h −1 . Compared with the most literature results, usually testing the catalysts at much lower GHSVs of below 120 L g −1 h −1 , 10,14,16,17,24 the catalyst reported here showed obvious advantages in catalytic activity and stability, particularly at room temperature.…”

“…13,17,19 Additionally, more oxygen vacancies were created by coating CeO 2 on the surface of ε-MnO 2 (ref. 24) as it could switch the oxidation states between Ce 3+ and Ce 4+ to form oxygen vacancies. 25 Besides, the degradation efficiency of polycyclic aromatic hydrocarbons could be enhanced via synergistic effects of Mn 3+ and oxygen vacancies.…”

Electrochemical Ce(III)/Ce(IV) Redox Behavior and Ce Oxide Nanostructure Recovery over Thio-Terpyridine-Functionalized Au/Carbon Paper Electrodes

“…Cerium (Ce) has widely been used and studied in diverse application areas of heterogeneous catalysts, redox flow batteries, solid-oxide fuel cells, and pyroprocessing technology. − The unique magnetic, catalytic, and electronic properties are originated from the partially filled 4f subshell in the lanthanide (Ln) element . Furthermore, because actinide (An) elements fill the 5f subshell, the physicochemical properties and redox behaviors of Ln and An ions are observed to be very similar .…”

“…For Ce­(III) and Ce­(IV) ions, the interconversion of the oxidation states is known to play a significant role in catalytic activity in solid Ce oxides. − For CeO 2 catalysts, the conversion of the +4 to +3 oxidation state induces oxygen vacancies and generally increases catalytic activity. − The Ce­(III)/Ce­(IV) redox couple in a liquid state, ,− the redox potential is known to be highly dependent on electrolyte media ranging from 1.28 V (vs the standard hydrogen electrode) in 1 M HCl to 1.74 V in 1 M HClO 4 . Different Gibbs free energies of Ce ions are the result of Ce­(III) and Ce­(IV) complexations with different anions. ,,, Thus, the redox potential is controlled by altering the electrolyte environment for a desired application.…”