Next Article in Journal
H3PW12O40/SBA-15 for the Solventless Synthesis of 3-Substituted Indoles
Previous Article in Journal
Improvement of the Photoelectrochemical Performance of TiO2 Nanorod Array by PEDOT and Oxygen Vacancy Co-Modification
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Catalysts
Volume 9
Issue 5
10.3390/catal9050408
catalysts-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Insights into the Morphological Effect of Co3O4 Crystallite on Catalytic Oxidation of Vinyl Chloride

by
Chao Wang
1,
Wenchao Hua
2,
Guangtao Chai
2,
Chuanhui Zhang
1,* and
Yanglong Guo
2,*
1
Institute of Materials for Energy and Environment, College of Materials Science and Engineering, Qingdao University, Qingdao 266071, China
2
Key Laboratory for Advanced Materials and Research, Institute of Industrial Catalysis, East China University of Science and Technology, Shanghai 200237, China
*
Authors to whom correspondence should be addressed.
Catalysts 2019, 9(5), 408; https://doi.org/10.3390/catal9050408
Submission received: 3 April 2019 / Revised: 21 April 2019 / Accepted: 27 April 2019 / Published: 30 April 2019
(This article belongs to the Section Environmental Catalysis)
Browse Figures
Versions Notes

Abstract

:
Co3O4 catalysts of cube and sphere shapes were prepared by one-step hydrothermal synthesis with different controlled amounts of Co(NO3)2·6H2O and NaOH. The morphological effects on both physicochemical properties and catalytic activities of vinyl chloride oxidation were investigated by material characterization and performance evaluation. The obtained results showed that the morphology, resulting in the exposure difference of crystal planes, significantly affected the catalytic property. The catalytic activity for vinyl chloride oxidation followed a descending order of Co3O4 cube (Co3O4-c) > Co3O4 sphere (Co3O4-s) > Co3O4 commercial (Co3O4-com). The cube-shaped Co3O4 presented higher catalytic activity and stability than Co3O4 spheres despite their similar crystallographic structures as well as physicochemical and redox properties. Accordingly, the different catalytic behaviors should be attributed to a morphological effect. The Co3O4 cube with a preferential exposure of (001) plane presented higher abundance of surface Co2+ cations and adsorbed oxygen species, which acted as the active sites responsible for the improvement of its catalytic activity.

Graphical Abstract

1. Introduction

A current global environmental issue is the atmospheric pollution arising from the emission of volatile organic compounds (VOCs), released from the combustion of fossil fuel and commercial waste exhausts such as petrochemical, industrial printing, and dry-cleaning processes. These emissions have adverse impacts on human health and the environment. As one of the promising technologies, catalytic oxidation could degrade VOC pollutants into harmless products with high selectivity. Thus, one of the most important research objectives for VOC oxidation is the preparation of highly efficient catalysts with good reaction stability.
Transition metal oxides are one kind of catalyst for VOCs oxidation, and are slightly less active than materials based on noble metals [1,2,3]. Nevertheless, their low cost and good resistance against poisoning by chlorine and sulfur species during the catalytic reaction are significantly highlighted. Among all, Co3O4 has been widely applied in many catalytic application [4,5,6,7,8], including VOC oxidation [9,10,11,12,13].
Co3O4 presents a spinel structure with an Fd-3m crystallographic space group, where oxygen atoms are arranged in a cubic close-packed matrix and the Co3+ and Co2+ cations are positioned in the octahedral and tetrahedral lattice sites, respectively [14,15]. The Co3O4 particles usually expose the lower index plane with (110), (111), and (001) planes [16], while the catalytic activity is likely related to high bulk oxygen mobility and highly active oxygen species [17,18]. Recent research has established that the tunable morphology of Co3O4 nanocrystals has a notable effect on CO or hydrocarbon oxidation [19], which was ascribed to the reactive preferential crystal planes with different shapes. For example, the nanorod-shaped Co3O4 privileges the presence of active Co3+ species on (110) planes, which were demonstrated to be the most active sites for CO adsorption. Thus, this nanorod structure can also catalyze the oxidation of CO at temperatures as low as -77 °C, keeping a constant stability in moist conditions [20]. Furthermore, it has been demonstrated that Co3+ species on (011) planes in nanobelt structures are more reactive than those on (001) planes in nanocubes [21]. From this viewpoint, a clear clarification of the morphology–activity relationship is of great significance for the development of novel catalytic materials. However, the correlation between the morphological features and catalytic activity of Co3O4 for chlorinated VOC oxidation has rarely been studied.
In this study, a Co3O4 catalyst with different morphologies (cube and sphere) was prepared, characterized, and investigated for the oxidation of vinyl chloride (VC), and the morphological effect of Co3O4 on both physicochemical characteristics and catalytic activities was extensively studied.

2. Results

2.1. Characterization Results

The inductively coupled plasma results in Table 1 show that all catalysts presented nearly the same weight percentage of Co (approximately 70 wt. %), which agree well with the theoretical value of Co3O4. The scanning electron microscope (SEM) images of the catalysts in Figure 1 demonstrate that the morphology of Co3O4 varied depending on the amount of Co(NO3)2·6H2O and NaOH during the preparation process, which is in agreement with previous reports [22]. Obviously, the synthesis with a lower concentration of cobalt nitrate resulted in the formation of the Co3O4-c with a particle size around 250 nm, seen in Figure 1a, while Co3O4-s could be obtained using a higher concentration of cobalt nitrate with similar particle size as Co3O4-c (Figure 1b). In contrast, Figure 1c shows that Co3O4-com presented an irregular particle size from 100 to 300 nm. In addition, the morphology of Co3O4-c was also confirmed by the transmission electron microscope (TEM) images in Figure 1d. According to the literature [23,24], the dominant exposed planes of cubic Co3O4 are six (001) planes.
The X-ray diffraction (XRD) patterns of the Co3O4 catalysts are presented in Figure 2. All diffraction peaks were indexed as the standard pure crystalline phase of Co3O4 (JCPDS file No. 42-1467) without any detection of impurities. Co3O4-c and Co3O4-s presented analogical XRD patterns with similar characteristic peaks. As seen in Table 1, the average crystallite size was estimated by applying the Scherrer equation. It was 62 nm for Co3O4-c, whereas it increased to 100 and 93 nm for Co3O4-s and Co3O4-com, respectively. Moreover, no obvious difference in the specific surface area of each catalyst was observed, which were 7, 7, and 6 m2·g−1 for Co3O4-c, Co3O4-s, and Co3O4-com, respectively.
Chemical surface compositions and valence states were determined by X-ray photoelectron spectroscopy (XPS), and the spectra of Co 2p and O 1s are displayed. In Figure 3a, the binding energy (B.E.) value of Co 2p3/2 and Co 2p1/2 was around 780 and 795 eV, respectively [14,25]. The satellite peaks at 785 eV confirmed the existence of Co2+ species in the octahedral sites [26,27,28]. Herein, the Co 2p spectra were resolved using a fitting procedure partially based on that suggested by Biesinger et al. [29]. The contributions from Co3+ and Co2+ cations were identified at 779.5 and 781.1 eV, respectively [30]. Additionally, two satellite peaks, S1 and S2, at 785.3 and 789.4 eV appeared due to electron correlations and final state effects in Co2+ and Co3+ cations, respectively [31]. In turn, the satellite S3 was attributed to the spin orbit contributions of Co 2p1/2 and also from satellites S1 and S2 [32,33,34].
Based on the quantitative analysis results in Table 1, the Co3+/Co2+ molar ratio over the Co3O4 catalysts followed an increasing order of Co3O4-c < Co3O4-s < Co3O4-com. The lower molar ratio of Co3+/Co2+ over Co3O4-c indicates that higher abundance of Co2+ cations were presented on the (001) plane of Co3O4-c, which could be a crucial factor for the catalytic oxidation of VOCs [14,35]. The O 1s spectra in Figure 3b were also decomposed into two peaks. The peaks located at 529.7 and 531.2 eV could be ascribed to lattice oxygen (Olatt, i.e., O2-) and adsorbed oxygen onto surface oxygen vacancies (Oads, i.e., O−, O22-, OH−, ), respectively [36,37]. According to the quantitative analysis of O 1s spectra, the Oads/Olatt ratio of Co3O4-c was higher than that obtained from other catalysts (Table 1), which indicates that Co3O4-c provided more surface-active oxygen species than others.
The H2-TPR profiles show that two reduction peaks were clearly observed over the Co3O4-c and Co3O4-s catalysts in Figure 4a. The two peaks at 285 and 330 °C were assigned to the reduction of Co3+ to Co2+ and Co2+ to metallic cobalt, respectively [38]. Comparatively, the Co3O4-com catalyst showed an overlapping peak, indicating a successive reduction behavior of Co3+ into Co2+ and Co0. Additionally, the temperature of reduction peaks maximum over Co3O4-c and Co3O4-s were relatively lower than that over Co3O4-com, suggesting that the cube- and sphere-shaped Co3O4 catalysts presented better reducibility. The low-temperature reducibility could be evaluated by the initial H2 consumption rate (less than 25% of oxygen consumption in the first reduction band of the H2-TPR profile) [39,40]. Figure 4b shows the initial H2 consumption rate versus inverse temperature over the Co3O4 catalysts. The initial H2 consumption rate over the catalysts decreased in the order of Co3O4-c > Co3O4-s > Co3O4-com, indicating that Co3O4-c exhibited the highest low-temperature reducibility. This trend is in good agreement with the order of the Oads/Olatt ratio.

2.2. Catalytic Performances for VC Oxidation

The catalytic performances of the Co3O4 catalysts were tested for the oxidation of VC, which acted as a model reaction for chlorinated VOCs. Based on the light-off curves shown in Figure 5 and the T50 and T90 values listed in Table 2, it could be found that the catalytic activity for VC over the catalysts followed Co3O4-c > Co3O4-s > Co3O4-com, which is similar to the TPR results.
The final products in the effluent gas were water (H2O), carbon dioxide (CO2), and hydrogen chloride (HCl), which were identified by online mass spectrometry. However, during the reaction of VC oxidation, highly chlorinated by-products were yielded and quantitatively determined. The major chlorinated organics were namely 1,1,2-trichloroethane (CH2ClCHCl2), dichloromethane (CH2Cl2), trichloromethane (CHCl3), and tetrachloromethane (CCl4). As presented in Figure 6, the concentrations of the chlorinated organics over Co3O4-c or Co3O4-s were relatively lower than those over Co3O4-com catalyst, which could be owning to their higher catalytic activity. Moreover, the temperature corresponding to the maximum formation of chlorinated organics in Figure 6 indicates that Co3O4-c or Co3O4-s also presented higher chlorination activity compared with Co3O4-com. Regarding the formation mechanism, CH2ClCHCl2 might be produced from the addition reaction between VC and the surface active chlorine species. Then, it could undergo catalytic cracking on Co3O4 catalysts, resulting in the formation of CH2Cl2, CHCl3, and CCl4.
Figure 7 displays the selectivities of HCl and CO2 at different reaction temperatures. At higher temperature, all VC was oxidized into HCl without the detection of other chlorinated by-products. However, the lowest HCl selectivity was obtained over Co3O4-c at the temperature range of 240 to 320 °C, which could be due to the simultaneous formation of high amounts of chlorinated by-products. The selectivity of HCl rose back to 100% with the temperature continuously increased, indicating the complete decomposition of chlorinated by-products. However, the selectivity for CO2 always remained above 90% over the Co3O4-c and Co3O4-s catalysts beneficially due to their higher reaction activity, confirming the good carbon balance in the reaction.
Finally, the catalytic durability for VC oxidation in long-term experiments (i.e., 40 h) was evaluated over the Co3O4 catalysts, as shown in Figure 8. Co3O4-com exhibited relatively poor stability, with the conversion at 40% at 360 °C. Comparatively, approximately the same VC conversion of 80% was observed over the Co3O4-c and Co3O4-s catalysts at lower temperatures of 330 °C and 350 °C, respectively. Co3O4-s maintained stable activity during the initial 15 h but gradually deactivated with more time, giving the conversion of 60%. Ultimately, Co3O4-c presented the relatively more stable VC conversion of 80%, confirming its higher catalytic stability.
Considering all of the results above, the lower catalytic activity and durability of Co3O4-com in the reactions could be associated with its poorer low-temperature reducibility, as well as the lower surface abundance of Co2+ and Oads species compared to those Co3O4 catalysts of unique morphology. However, despite the close crystallographic structure and similar physicochemical properties, Co3O4-c presented higher catalytic activity and stability for VC oxidation than Co3O4-s, which reveals the close relation of catalytic reactivity with the morphological effect. Especially, the Co3O4-c catalyst with a preferential exposure of (001) planes possesses more Co2+ cations on the surface of cubic structure. It was proven that the higher abundance of Co2+ correlated well with higher oxygen mobility, thus resulting in the significant improvement of catalytic activity.

3. Materials and Methods

3.1. Co3O4 Preparation

All chemicals throughout the experiment were analytically pure and not further purified. Co(NO3)2·6H2O and NaOH were provided by Sinopharm Chemical Reagent Co., Ltd. The Co3O4 catalyst was prepared by a hydrothermal process as reported in [22,23] with some modifications. Specifically, both Co(NO3)2·6H2O and NaOH were dissolved in 30 mL deionized water and kept stirring for 30 min. Subsequently, the solution was transferred into a Teflon-lined stainless-steel autoclave and then treated at 180 °C for 3 h. After cooling down to room temperature, the obtained product was filtrated, washed several times with ethanol, and further dried at 60 °C. Finally, a calcination at 500 °C for 3 h in air was conducted to yield the Co3O4 material. For the synthesis of Co3O4 cube (Co3O4-c), the amount of Co(NO3)2·6H2O and NaOH was 8.73 g and 0.30 g, respectively. A total of 17.46 g Co(NO3)2·6H2O and 0.30 g NaOH were used for the preparation of Co3O4 sphere (Co3O4-s). For comparison, a commercial Co3O4 (Co3O4-com) purchased from Aladdin Co. Ltd was also used.

3.2. Characterizations

Elemental analysis of Co content in the catalysts was conducted using inductively coupled plasma (ICP) on a HORIBA Jobin Yvon Activa instrument (HORIBA, Paris, France). X-ray diffraction (XRD) patterns of the catalyst were recorded by a Bruker D8 Advance A25 with Cu Kα radiation (λ = 0.154184 nm) at 50 kV and 35 mA. The nitrogen sorption was measured at 77 K on a Micromeritics ASAP 2020 apparatus after a degassing pretreatment. The specific surface area was calculated by the Brunauer–Emmett–Teller (BET) method. Temperature-programmed reduction of hydrogen (H2-TPR) was performed on a Micromeritics AutoChem 2920 apparatus using 10 vol% H2/Ar (50 mL∙min−1) as the reducing gas. The reduction temperature increased from 50 to 800 °C at a rate of 10 °C∙min−1, and the H2 consumption was measured by a thermal conductivity detector (TCD). X-ray photoelectron spectroscopy (XPS) analysis was carried out on a Kratos Axis Ultra DLD electron spectrometer using an AlKα (1486.6 eV) radiation source. The binding energy of C 1s electron (284.6 eV) was used to calibrate the spectra. Scanning electron microscopy (SEM) was performed on a JEOL JSM-7800F microscope (JEOL, Tokyo, Japan), while transmission electron microscopy (TEM) was performed on a JEOL JEM-2100 microscope (JEOL, Tokyo, Japan).

3.3. Catalytic Tests

Catalytic oxidation of VC was performed using a fixed-bed reactor at atmospheric pressure. A total of 0.10 g of the Co3O4 catalyst was used under the flow rate of 80 mL∙min−1 containing 1000 ppm VC diluted by air. VC and other organics were analyzed by an online PerkinElmer Clarus 580 GC with a flame ionization detector (FID) in a steady state.
The VC conversion was determined according to Equation (1),
VC conversion (%) = (1 − [VC]out/[VC]in) * 100,
where [VC]in and [VC]out represent the VC concentrations of inlet and outlet, respectively. The HCl and CO2 selectivity were calculated based on Cl and C balance according to Equations (2) and (3), respectively. [HCl] and [CO2] represent the HCl and CO2 concentrations of the outlet.
HCl selectivity (%) = [HCl]/([VC]in − [VC]out)
CO2 selectivity (%) = 0.5*[CO2]/([VC]in − [VC]out)

4. Conclusions

In this work, we prepared Co3O4 catalysts with different shapes (cubic and spherical) and comparatively evaluated their catalytic performances for VC oxidation with that of the commercial Co3O4 material. The Co3O4-c catalyst exhibited the optimum catalytic activity and stability in the reaction, which could be attributed to its higher abundance of exposed Co2+ cations on the surface of the cube structure, acting as the active sites for oxidation reaction. This work provides clear evidence of the morphological effect on the catalytic behavior in VOC oxidation processes.

Author Contributions

Funding acquisition, C.W., C.Z., Y.G.; investigation, C.W., W.H., G.C.; supervision, Y.G.; writing—original draft preparation, C.W.; writing—review and editing, C.Z.

Funding

This research was funded by the National Key Research and Development Program of China (2016YFC0204300), the National Natural Science Foundation of China (21577035 and 21607163), the China Postdoctoral Science Foundation (2017M622139 and 2018M630754), and the Qingdao Postdoctoral Application Research.

Acknowledgments

We are grateful to Sonia Gil (S.G.) and Anne Giroir-Fendler (A.G.). We thank all the co-workers in the group of A.G. from Institut de Recherches sur la Catalyse et l’Environnement de Lyon. C.W. and C.Z. were as a joint student under the supervision of A.G, while G.C. is now as a joint student in this group.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Yu, Q.; Wang, C.; Li, X.; Li, Z.; Wang, L.; Zhang, Q.; Wu, G.; Li, Z. Engineering an effective MnO2 catalyst from LaMnO3 for catalytic methane combustion. Fuel 2019, 239, 1240–1245. [Google Scholar] [CrossRef]
  2. Luo, D.; Chen, B.; Li, X.; Liu, Z.; Liu, X.; Liu, X.; Shi, C.; Zhao, X.S. Three-dimensional nitrogen-doped porous carbon anchored CeO2 quantum dots as an efficient catalyst for formaldehyde oxidation. J. Mater. Chem. A 2018, 6, 7897–7902. [Google Scholar] [CrossRef]
  3. Zhang, C.; Huang, H.; Li, G.; Wang, L.; Song, L.; Li, X. Zeolitic acidity as a promoter for the catalytic oxidation of toluene over MnOx/HZSM-5 catalysts. Catal. Today 2019, 327, 374–381. [Google Scholar] [CrossRef]
  4. Du, Y.; Huang, W.; Hua, Z.; Wang, Y.; Cui, X.; Wu, M.; Shu, Z.; Zhang, L.; Wang, J.; Chen, H.; et al. A facile ultrasonic process for the preparation of Co3O4 nanoflowers for room-temperature removal of low-concentration NOx. Catal. Commun. 2014, 57, 73–77. [Google Scholar] [CrossRef]
  5. Park, J.-Y.; Lee, Y.-J.; Karandikar, P.R.; Jun, K.-W.; Ha, K.-S.; Park, H.-G. Fischer–Tropsch catalysts deposited with size-controlled Co3O4 nanocrystals: Effect of Co particle size on catalytic activity and stability. Appl. Catal. A 2012, 411–412, 15–23. [Google Scholar] [CrossRef]
  6. del Río, L.; López, I.; Marbán, G. Stainless steel wire mesh-supported Co3O4 catalysts in the steam reforming of ethanol. Appl. Catal. B 2014, 150–151, 370–379. [Google Scholar] [CrossRef]
  7. Bi, L.; Shafi, S.P.; Da’as, E.H.; Traversa, E. Tailoring the Cathode–Electrolyte Interface with Nanoparticles for Boosting the Solid Oxide Fuel Cell Performance of Chemically Stable Proton-Conducting Electrolytes. Small 2018, 14, 1801231. [Google Scholar] [CrossRef] [PubMed]
  8. Wang, B.; Bi, L.; Zhao, X. Liquid-phase synthesis of SrCo0. 9Nb0. 1O3-δ cathode material for proton-conducting solid oxide fuel cells. Ceram. Int. 2018, 44, 5139–5144. [Google Scholar] [CrossRef]
  9. Teng, F.; Chen, M.; Li, G.; Teng, Y.; Xu, T.; Hang, Y.; Yao, W.; Santhanagopalan, S.; Meng, D.D.; Zhu, Y. High combustion activity of CH4 and catalluminescence properties of CO oxidation over porous Co3O4 nanorods. Appl. Catal. B 2011, 110, 133–140. [Google Scholar] [CrossRef]
  10. Garcia, T.; Agouram, S.; Sánchez-Royo, J.F.; Murillo, R.; Mastral, A.M.; Aranda, A.; Vázquez, I.; Dejoz, A.; Solsona, B. Deep oxidation of volatile organic compounds using ordered cobalt oxides prepared by a nanocasting route. Appl. Catal. A 2010, 386, 16–27. [Google Scholar] [CrossRef]
  11. de Rivas, B.; López-Fonseca, R.; Jiménez-González, C.; Gutiérrez-Ortiz, J.I. Synthesis, characterisation and catalytic performance of nanocrystalline Co3O4 for gas-phase chlorinated VOC abatement. J. Catal. 2011, 281, 88–97. [Google Scholar] [CrossRef]
  12. Li, G.; Zhang, C.; Wang, Z.; Huang, H.; Peng, H.; Li, X. Fabrication of mesoporous Co3O4 oxides by acid treatment and their catalytic performances for toluene oxidation. Appl. Catal. A 2018, 550, 67–76. [Google Scholar] [CrossRef]
  13. Bai, B.; Arandiyan, H.; Li, J. Comparison of the performance for oxidation of formaldehyde on nano-Co3O4, 2D-Co3O4, and 3D-Co3O4 catalysts. Appl. Catal. B 2013, 142–143, 677–683. [Google Scholar] [CrossRef]
  14. Cai, T.; Huang, H.; Deng, W.; Dai, Q.; Liu, W.; Wang, X. Catalytic combustion of 1,2-dichlorobenzene at low temperature over Mn-modified Co3O4 catalysts. Appl. Catal. B 2015, 166–167, 393–405. [Google Scholar] [CrossRef]
  15. Wang, X.; Chen, X.; Gao, L.; Zheng, H.; Zhang, Z.; Qian, Y. One-dimensional arrays of Co3O4 nanoparticles:  synthesis, characterization, and optical and electrochemical properties. J. Phys. Chem. B 2004, 108, 16401–16404. [Google Scholar] [CrossRef]
  16. Hu, L.; Peng, Q.; Li, Y. Selective synthesis of Co3O4 nanocrystal with different shape and crystal plane effect on catalytic property for methane combustion. J. Am. Chem. Soc. 2008, 130, 16136–16137. [Google Scholar] [CrossRef]
  17. Wang, C.; Zhang, C.; Hua, W.; Guo, Y.; Lu, G.; Gil, S.; Giroir-Fendler, A. Catalytic oxidation of vinyl chloride emissions over Co-Ce composite oxide catalysts. Chem. Eng. J. 2017, 315, 392–402. [Google Scholar] [CrossRef]
  18. Zhang, C.; Wang, C.; Zhan, W.; Guo, Y.; Guo, Y.; Lu, G.; Baylet, A.; Giroir-Fendler, A. Catalytic oxidation of vinyl chloride emission over LaMnO3 and LaB0.2Mn0.8O3(B=Co, Ni, Fe) catalysts. Appl. Catal. B 2013, 129, 509–516. [Google Scholar] [CrossRef]
  19. Wang, C.; Zhang, C.; Hua, W.; Guo, Y.; Lu, G.; Gil, S.; Giroir-Fendler, A. Low-temperature catalytic oxidation of vinyl chloride over Ru modified Co3O4 catalysts. RSC Adv. 2016, 6, 99577–99585. [Google Scholar] [CrossRef]
  20. Xie, X.; Li, Y.; Liu, Z.-Q.; Haruta, M.; Shen, W. Low-temperature oxidation of CO catalysed by Co3O4 nanorods. Nature 2009, 458, 746–749. [Google Scholar] [CrossRef]
  21. Hu, L.; Sun, K.; Peng, Q.; Xu, B.; Li, Y. Surface active sites on Co3O4 nanobelt and nanocube model catalysts for CO oxidation. Nano Res. 2010, 3, 363–368. [Google Scholar] [CrossRef]
  22. Xia, S.; Yu, M.; Hu, J.; Feng, J.; Chen, J.; Shi, M.; Weng, X. A model of interface-related enhancement based on the contrast between Co3O4 sphere and cube for electrochemical detection of hydrogen peroxide. Electrochem. Commun. 2014, 40, 67–70. [Google Scholar] [CrossRef]
  23. Xiao, X.; Liu, X.; Zhao, H.; Chen, D.; Liu, F.; Xiang, J.; Hu, Z.; Li, Y. Facile shape control of Co3O4 and the effect of the crystal plane on electrochemical performance. Adv. Mater. 2012, 24, 5762–5766. [Google Scholar] [CrossRef]
  24. Zhang, Y.; Ding, F.; Deng, C.; Zhen, S.; Li, X.; Xue, Y.; Yan, Y.-M.; Sun, K. Crystal plane-dependent electrocatalytic activity of Co3O4 toward oxygen evolution reaction. Catal. Commun. 2015, 67, 78–82. [Google Scholar] [CrossRef]
  25. Konsolakis, M.; Sgourakis, M.; Carabineiro, S.A.C. Surface and redox properties of cobalt-ceria binary oxides: on the effect of Co content and pretreatment conditions. Appl. Surf. Sci. 2015, 341, 48–54. [Google Scholar] [CrossRef]
  26. Barreca, D.; Massignan, C.; Daolio, S.; Fabrizio, M.; Piccirillo, C.; Armelao, L.; Tondello, E. Composition and microstructure of cobalt oxide thin films obtained from a novel cobalt(II) precursor by chemical vapor deposition. Chem. Mater. 2001, 13, 588–593. [Google Scholar] [CrossRef]
  27. Wei, W.; Chen, W.; Ivey, D.G. Rock salt-spinel structural transformation in anodically electrodeposited Mn-Co-O nanocrystals. Chem. Mater. 2008, 20, 1941–1947. [Google Scholar] [CrossRef]
  28. Tian, Z.; Tchoua Ngamou, P.H.; Vannier, V.; Kohse-Höinghaus, K.; Bahlawane, N. Catalytic oxidation of VOCs over mixed Co-Mn oxides. Appl. Catal. B 2012, 117–118, 125–134. [Google Scholar] [CrossRef]
  29. Biesinger, M.C.; Payne, B.P.; Grosvenor, A.P.; Lau, L.W.M.; Gerson, A.R.; Smart, R.S.C. Resolving surface chemical states in XPS analysis of first row transition metals, oxides and hydroxides: Cr, Mn, Fe, Co and Ni. Appl. Surf. Sci. 2011, 257, 2717–2730. [Google Scholar] [CrossRef]
  30. Díaz-Fernández, D.; Méndez, J.; Bomatí-Miguel, O.; Yubero, F.; Mossanek, R.J.O.; Abbate, M.; Domínguez-Cañizares, G.; Gutiérrez, A.; Tougaard, S.; Soriano, L. The growth of cobalt oxides on HOPG and SiO2 surfaces: A comparative study. Surf. Sci. 2014, 624, 145–153. [Google Scholar] [CrossRef]
  31. Lykhach, Y.; Faisal, F.; Skála, T.; Neitzel, A.; Tsud, N.; Vorokhta, M.; Dvořák, F.; Beranová, K.; Kosto, Y.; Prince, K.C.; et al. Interplay between the metal-support interaction and stability in Pt/Co3O4 (111) model catalysts. J. Mater. Chem. A 2018, 6, 23078–23086. [Google Scholar] [CrossRef]
  32. Chen, J.; Shi, W.; Yang, S.; Arandiyan, H.; Li, J. Distinguished roles with various vanadium loadings of CoCr2–xVxO4 (x=0-0.20) for methane combustion. J. Phys. Chem. C 2011, 115, 17400–17408. [Google Scholar] [CrossRef]
  33. Wang, Y.; Jia, A.; Luo, M.; Lu, J. Highly active spinel type CoCr2O4 catalysts for dichloromethane oxidation. Appl. Catal. B 2015, 165, 477–486. [Google Scholar] [CrossRef]
  34. Gautier, J.L.; Rios, E.; Gracia, M.; Marco, J.F.; Gancedo, J.R. Characterisation by X-ray photoelectron spectroscopy of thin MnxCo3−xO4(1≥x≥0) spinel films prepared by low-temperature spray pyrolysis. Thin Solid Films 1997, 311, 51–57. [Google Scholar] [CrossRef]
  35. Aristizábal, B.H.; de Correa, C.M.; Serykh, A.I.; Hetrick, C.E.; Amiridis, M.D. In situ FTIR study of the adsorption and reaction of ortho-dichlorobenzene over Pd-promoted Co-HMOR. Microporous Mesoporous Mater. 2008, 112, 432–440. [Google Scholar] [CrossRef]
  36. Valeri, S.; Borghi, A.; Gazzadi, G.C.; di Bona, A. Growth and structure of cobalt oxide on (001) bct cobalt film. Surf. Sci. 1999, 423, 346–356. [Google Scholar] [CrossRef]
  37. Zhang, C.; Wang, C.; Hua, W.; Guo, Y.; Lu, G.; Gil, S.; Giroir-Fendler, A. Relationship between catalytic deactivation and physicochemical properties of LaMnO3 perovskite catalyst during catalytic oxidation of vinyl chloride. Appl. Catal. B 2016, 186, 173–183. [Google Scholar] [CrossRef]
  38. De Rivas, B.; López-Fonseca, R.; Jiménez-González, C.; Gutiérrez-Ortiz, J.I. Highly active behaviour of nanocrystalline Co3O4 from oxalate nanorods in the oxidation of chlorinated short chain alkanes. Chem. Eng. J. 2012, 184, 184–192. [Google Scholar] [CrossRef]
  39. Liu, Y.; Dai, H.; Du, Y.; Deng, J.; Zhang, L.; Zhao, Z.; Au, C.T. Controlled preparation and high catalytic performance of three-dimensionally ordered macroporous LaMnO3 with nanovoid skeletons for the combustion of toluene. J. Catal. 2012, 287, 149–160. [Google Scholar] [CrossRef]
  40. Liu, Y.; Dai, H.; Du, Y.; Deng, J.; Zhang, L.; Zhao, Z. Lysine-aided PMMA-templating preparation and high performance of three-dimensionally ordered macroporous LaMnO3 with mesoporous walls for the catalytic combustion of toluene. Appl. Catal. B 2012, 119–120, 20–31. [Google Scholar] [CrossRef]
Catalysts 09 00408 g001a 550Catalysts 09 00408 g001b 550
Figure 1. SEM images of (a) Co3O4-c, (b) Co3O4-s, (c) Co3O4-com, and a TEM image of (d) Co3O4-c.
Figure 1. SEM images of (a) Co3O4-c, (b) Co3O4-s, (c) Co3O4-com, and a TEM image of (d) Co3O4-c.
Catalysts 09 00408 g001aCatalysts 09 00408 g001b
Catalysts 09 00408 g002 550
Figure 2. XRD patterns of the Co3O4 catalysts.
Figure 2. XRD patterns of the Co3O4 catalysts.
Catalysts 09 00408 g002
Catalysts 09 00408 g003 550
Figure 3. (a) Co 2p and (b) O 1s XPS spectra of the Co3O4 catalysts.
Figure 3. (a) Co 2p and (b) O 1s XPS spectra of the Co3O4 catalysts.
Catalysts 09 00408 g003
Catalysts 09 00408 g004 550
Figure 4. (a) H2-TPR profiles and (b) the initial H2 consumption rate as a function of inverse temperature of the Co3O4 catalysts.
Figure 4. (a) H2-TPR profiles and (b) the initial H2 consumption rate as a function of inverse temperature of the Co3O4 catalysts.
Catalysts 09 00408 g004
Catalysts 09 00408 g005 550
Figure 5. The light-off curves of vinyl chloride (VC) oxidation as a function of reaction temperature over the Co3O4 catalysts (reaction conditions: 1000 ppm VC, air balanced, and weight hourly space velocity (WHSV) = 48,000 mL g−1 h−1).
Figure 5. The light-off curves of vinyl chloride (VC) oxidation as a function of reaction temperature over the Co3O4 catalysts (reaction conditions: 1000 ppm VC, air balanced, and weight hourly space velocity (WHSV) = 48,000 mL g−1 h−1).
Catalysts 09 00408 g005
Catalysts 09 00408 g006 550
Figure 6. The chlorinated by-product distributions for vinyl chloride (VC) catalytic oxidation over the Co3O4 catalysts: (a) 1,1,2-trichloroethane (CH2Cl–CHCl2), (b) dichloromethane (CH2Cl2), (c) trichloromethane (CHCl3), and (d) tetrachloromethane (CCl4) (reaction conditions: 1000 ppm VC, air balanced, and WHSV= 48,000 mL g−1 h−1).
Figure 6. The chlorinated by-product distributions for vinyl chloride (VC) catalytic oxidation over the Co3O4 catalysts: (a) 1,1,2-trichloroethane (CH2Cl–CHCl2), (b) dichloromethane (CH2Cl2), (c) trichloromethane (CHCl3), and (d) tetrachloromethane (CCl4) (reaction conditions: 1000 ppm VC, air balanced, and WHSV= 48,000 mL g−1 h−1).
Catalysts 09 00408 g006
Catalysts 09 00408 g007 550
Figure 7. The selectivity for (a) CO2 and (b) HCl over the Co3O4 catalysts (reaction conditions: 1000 ppm vinyl chloride (VC), air balanced, and WHSV = 48,000 mL g−1 h−1).
Figure 7. The selectivity for (a) CO2 and (b) HCl over the Co3O4 catalysts (reaction conditions: 1000 ppm vinyl chloride (VC), air balanced, and WHSV = 48,000 mL g−1 h−1).
Catalysts 09 00408 g007
Catalysts 09 00408 g008 550
Figure 8. Long-term catalytic durability as a function of time on stream for vinyl chloride (VC) oxidation over the Co3O4 catalysts (reaction conditions: 1000 ppm VC, air balanced, and WHSV = 48,000 mL g−1 h−1).
Figure 8. Long-term catalytic durability as a function of time on stream for vinyl chloride (VC) oxidation over the Co3O4 catalysts (reaction conditions: 1000 ppm VC, air balanced, and WHSV = 48,000 mL g−1 h−1).
Catalysts 09 00408 g008
Table
Table 1. The Co content, crystallite size and surface atomic ratios of the Co3O4 catalysts.
Table 1. The Co content, crystallite size and surface atomic ratios of the Co3O4 catalysts.
CatalystsCo content
(wt. %)		Crystallite size
(nm)		Co3+/Co2+
(at./at.)		Oads/Olatt
(at./at.)
Co3O4-c71.6621.350.60
Co3O4-s71.61001.410.53
Co3O4-com70.2931.460.49
Table
Table 2. T50 and T90 values for the catalytic oxidation of vinyl chloride (VC) over the Co3O4 catalysts.
Table 2. T50 and T90 values for the catalytic oxidation of vinyl chloride (VC) over the Co3O4 catalysts.
CatalystsT50 (°C)T90 (°C)
Co3O4-c308340
Co3O4-s320372
Co3O4-com372431

Share and Cite

MDPI and ACS Style

Wang, C.; Hua, W.; Chai, G.; Zhang, C.; Guo, Y. Insights into the Morphological Effect of Co3O4 Crystallite on Catalytic Oxidation of Vinyl Chloride. Catalysts 2019, 9, 408. https://doi.org/10.3390/catal9050408

AMA Style

Wang C, Hua W, Chai G, Zhang C, Guo Y. Insights into the Morphological Effect of Co3O4 Crystallite on Catalytic Oxidation of Vinyl Chloride. Catalysts. 2019; 9(5):408. https://doi.org/10.3390/catal9050408

Chicago/Turabian Style

Wang, Chao, Wenchao Hua, Guangtao Chai, Chuanhui Zhang, and Yanglong Guo. 2019. "Insights into the Morphological Effect of Co3O4 Crystallite on Catalytic Oxidation of Vinyl Chloride" Catalysts 9, no. 5: 408. https://doi.org/10.3390/catal9050408

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop