Co3O4 Nanorods with a Great Amount of Oxygen Vacancies for Highly Efficient Hg0 Oxidation from Coal Combustion Flue Gas

Huang

et al. 2020

Ind. Eng. Chem. Res.

The inherent low activity at room temperature has greatly limited the utilization of Co 3 O 4 in indoor air purification. In this work, an extremely facile and mild method utilizing the strong oxidation of H 2 O 2 was designed to prepare a novel Co 3 O 4 -HP catalyst. The Co 3 O 4 -HP catalyst exhibits excellent removal activity for low-level concentration (∼1 ppm) of formaldehyde (HCHO) at room temperature. Under the static test mode, it shows 90.62% HCHO removal efficiency in 180 min at an RH of ∼55%. Under the dynamic test mode, it maintains the performance to remove approximately 97.26% of HCHO within 180 min under a GHSV of ∼90,000 mL•h −1 •g −1 . Additionally, the HCHO removal efficiency of Co 3 O 4 -HP is also maintained at around 94.76% under a higher GHSV of ∼150,000 mL•h −1 •g −1 . Such a satisfying activity is due to abundant oxygen vacancy defects bringing about a large number of surface reactive oxygen species and high redox capacity and oxygen migration capacity. It is also because of the synergistic effect of surface OH groups. This strategy will open an exciting avenue to design outstanding catalysts for HCHO removal by defect engineering and the synergistic effect.

Section: Resultsmentioning

confidence: 89%

Defect Engineering and Synergistic Effect in Co₃O₄ Catalysts for Efficient Removal of Formaldehyde at Room Temperature

Huang

et al. 2020

Ind. Eng. Chem. Res.

“…Co 3+ corresponded to the adsorption and activation of surface oxygen; so, a higher concentration of Co 3+ could increase the activity of the catalysts. 41 As shown in Figure 5C, the Ce 3d signal can be separated into eight peaks. In general, the Ce 3d 5/2 and Ce 3d 3/2 spin− orbit states were denoted as u and v, respectively.…”

Section: Resultsmentioning

confidence: 97%

“…It was noticed that the CeO 2 @Co 3 O 4 sample had a higher molar ratio of Co 3+ to Co 2+ than pure Co 3 O 4 , suggesting that there were more Co 3+ existing on the surface of CeO 2 @Co 3 O 4 . Co 3+ corresponded to the adsorption and activation of surface oxygen; so, a higher concentration of Co 3+ could increase the activity of the catalysts …”

Section: Resultsmentioning

confidence: 99%

Zeolitic Imidazolate Framework-67-Derived CeO₂@Co₃O₄ Core–Shell Microspheres with Enhanced Catalytic Activity toward Toluene Oxidation

Fang

Zhou

et al. 2020

Ind. Eng. Chem. Res.

In this work, a core–shell structured CeO2@Co3O4 catalyst was successfully prepared by using a zeolitic imidazolate framework-based material as a sacrificial template. The structure, morphology, and physicochemical characteristics of these materials were investigated by X-ray diffraction, N2 sorption, Fourier transform infrared spectroscopy, Raman spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, temperature-programmed desorption, and temperature-programmed reduction studies. Compared with pure Co3O4 and CeO2, the CeO2@Co3O4 sample displayed superior catalytic performance (T 90 = 225 °C) toward toluene oxidation. Results demonstrated that the CeO2@Co3O4 sample exhibited a core–shell structure, with hierarchically wrinkled surfaces. This unique structure, especially the interface between the core and the shell, endowed the CeO2@Co3O4 catalyst with better activity. In addition, there was a synergistic effect between cerium and cobalt oxides in the core–shell bimetallic sample, which was responsible for the improved performance of the material. Moreover, surface-active oxygen species involved and played a significant role in toluene oxidation.

“…Transition metal oxide Co3O4 has proved to have good Hg 0 oxidation performance. (Zhang et al, 2019a;Yang et al, 2020) It's a promising non-noble metal catalyst for Hg 0 removal. It can remove mercury efficiently at high temperatures, and it is more economical than precious metal catalysts.…”

Section: Introductionmentioning

confidence: 99%

“…(Yang et al, 2014) The Hg 0 removal temperature windows of the Ce-Co catalyst and Co3O4 nanorods synthesized by He et al were 150-350 ℃ and 100-300 ℃, respectively. (Zhang et al, 2017;Zhang et al, 2019b) Therefore, users need to create a specific temperature environment for Co3O4 to achieve its best performance. In the meanwhile, the internal environment of the flue gas purification system was complicated.…”

Section: Introductionmentioning

confidence: 99%

A novel nano-sized Co3O4@C catalyst derived from Co-MOF template for efficient Hg0 removal at low temperatures with outstanding SO2 resistance

Zhou

Shen

Yang

et al. 2021

Environ Sci Pollut Res

Co3O4 is a promising Hg 0 removal catalyst for industrial application. Operating temperature and low sulfur resistance are two of the main problems that hinder its industrial application in Hg removal. Herein, a metal-organic framework (Co-BDC) was introduced as a sacrificial template to obtain the catalyst nano-sized Co3O4@C by calcination. Part of the organic ligands carbonized during the calcination. Carbon wrapped Co3O4 and reduced metal agglomeration. The optimal Hg 0 removal temperature of the existing cobalt oxides catalysts was always around 150 ℃, but H2-TPR showed that the oxygen atoms on the Co3O4@C were more active than those on commercial Co3O4, causing the Hg 0 removal temperature window of Co3O4@C to shift to lower temperatures. The Hg 0 removal efficiency of Co3O4@C could reach almost 100% even at 25 ℃. In the meanwhile, Co3O4@C also showed a strong SO2 resistance at ambient temperature. Experimental results and characterization proved that SO2 did not compete with Hg 0 on the surface of Co3O4 at low temperatures. On the contrary, it participated in the oxidation of Hg 0 . This is a great improvement for Co3O4 catalyst in Hg 0 removal. It reduces the restrictions on the application of Co3O4 in Hg 0 removal. Co3O4@C shows considerable potential as an Hg 0 removal catalyst.