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Article

Ce1−xFexVO4 with Improved Activity for Catalytic Reduction of NO with NH3

1
College of Biology and Environmental Engineering, Zhejiang Shuren University, Hangzhou 310015, China
2
Key Laboratory of Inorganic Functional Materials, School of Chemistry and Chemical Engineering, Huangshan University, Huangshan 245041, China
3
School of Information Engineering, Huangshan University, Huangshan 245041, China
4
State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China
5
Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, China
6
Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China
*
Author to whom correspondence should be addressed.
Submission received: 15 March 2022 / Revised: 9 May 2022 / Accepted: 11 May 2022 / Published: 17 May 2022
(This article belongs to the Section Catalytic Materials)

Abstract

:
A series of Ce1−xFexVO4 (x = 0, 0.25, 0.50, 0.75, 1) catalysts prepared by modified hydrothermal synthesis were used for selective catalytic reduction (SCR) of NOx with NH3. Among them, Ce0.5Fe0.5VO4 showed the highest catalytic activity. The catalysts were characterized by X-ray diffraction (XRD), N2 adsorption–desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), X-ray fluorescence (XRF), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction using H2 (H2-TPR), and temperature-programmed desorption of NH3 (NH3-TPD). The results indicated the formation of Ce-Fe-V-O solid solutions. The average oxidation states (AOS) of Ce, Fe, V, and O atoms changed obviously with the incorporation of Fe3+ into CeVO4, and the acidity of Ce0.5Fe0.5VO4 differs from that of CeVO4 and FeVO4. The presence of more acid sites and a sharp increase in active oxygen species in Ce0.5Fe0.5VO4 effectively improved the selective catalytic reduction (SCR) activity.

1. Introduction

NOx pollutants released from power plants and car emissions have attracted much concern for their serious harm to the atmospheric environments and human health. The selective catalytic reduction (SCR) of NOx with NH3 has been extensively studied as one of the most effective methods to remove NOx [1,2,3]. V2O5-WO3-TiO2 is the most widely used SCR catalyst for its extraordinarily high activity in NO reduction. However, it generally operates in a high-temperature window (300–400 °C), and it can be deactivated by the flue gas containing H2O/SO2, phosphorus, ash, and alkali metals [4,5]. CeO2-based materials have been studied as either catalysts or catalyst supports due to their excellent redox property and oxygen-storage capacity [6]. These catalysts include CeO2-WO3-TiO2 [7], CeO2-ZrO2-WO3 [8], Mn/Ce-ZrO2 [9], MnOx-CeO2 [10], Sn-MnOx-CeO2 [11], MnOx-CeO2 [12], and V2O5/CeO2 [13]. However, CeO2-based catalysts may suffer from sulfation [14].
Metal vanadates (AVO4, A = La, Fe, Ce, etc.) is another kind of catalysts attracting attention. The reported AVO4-based catalysts include FeVO4/TiO2 [15], Ni-FeVO4/TiO2 [16], FexEr1−xVO4 [17], Sn-CeVO4 [18], Sb-CeVO4 [19], Ce0.5RM0.5VO4 (RM = Tb, Er, or Yb) [20], LaVO4/TiO2-WO3-SiO2 [21], CeV1−xWxO4 [22], and Zr-CeVO4/TiO2 [23]. For instance, Zr-CeVO4/TiO2 has high N2 selectivity and H2O/SO2 durability in NH3-SCR [23]. However, further promotion of AVO4 is needed [24,25].
Generally, there are two approaches to design better NH3-SCR catalysts. One approach is to modify the primary catalyst with one metal oxide or multiple metal oxides. The other approach is to modify supports used to disperse transition metal oxides [26]. In particular, the formation of metal oxide solid solutions may lead to better catalytic properties [27], since it may increase the catalyst’s surface area, thermal stability, and the number of active oxygen sites.
Previous research reported that Sn, Zr, La, etc., were doped into CeVO4 [18,22,24,28] separately to investigate their influences on NO conversion. For instance, Huang et al. developed Sn0.20Ce0.80VO4 for NH3-SCR by citric-acid-assisted solvothermal synthesis and post-hydrothermal treatment [18]. Zhao et al. developed Ce0.85Zr0.15VO4 for NH3-SCR [24]. However, the content of Sn or Zr in the solid solutions was not very high. Kang et al. synthesized a series of FeδCe1−δVO4 (δ ≤ 0.4) catalysts with good SO2 tolerance and NO conversion activity by a hydrothermal method [14]. The highest NO conversion appeared at δ = 0.3 for FeδCe1−δVO4 (δ ≤ 0.4). When the Fe content was higher, minor segregation of CeO2 occurred.
In this paper, Ce1−xFexVO4 (x ≤ 0.75) solid solutions were prepared by a modified sol-gel hydrothermal method. The objective of our research was to incorporate more Fe into the solid solution to increase the number of active oxygen sites, facilitate the interactions among Ce, Fe, and V in fully mixed solid solutions, and achieve high activity in NH3-SCR.

2. Results and Discussion

2.1. Catalytic Performance

Figure 1 depicts the NOx conversions on five catalysts, in the reaction temperature range of 150–400 °C. The NOx conversion on these catalysts increases as the temperature increases from 150 to 300 °C, and then decreases. Among them, Ce0.5Fe0.5O4 gives the highest NOx conversion (75.3%) at 300 °C. The catalytic activities of FeVO4 and CeVO4 are lower than those of Ce1−xFexVO4. The overall activity of these catalysts follows the trend of CeVO4 < Ce0.75Fe0.25VO4 < Ce0.5Fe0.5VO4 > Ce0.25Fe0.75VO4 > FeVO4, and the catalytic data are reproducible (Figure S1 in Supplementary Materials). It should be mentioned that the objective of this research was to identify the activity trends among these catalysts, i.e., to identify the best catalyst and understand why it is better than other catalysts. In addition, a small catalyst weight (200 mg) and a high flow rate (1000 mL/min) were adopted herein. Thus, the highest conversion was not 100%. Nevertheless, complete conversion can usually be achieved easily when more catalyst is used or the flow rate of the gas is decreased [27].
The stability of the optimal catalyst (Ce0.5Fe0.5VO4) at 300 °C was tested as a function of time on stream. As shown in Figure S2 from Supplementary Materials, the NOx conversion increases slightly in the initial 100 min, and it then becomes stable (74–75% conversion).
To set the result in perspective, the catalytic activity of Ce0.5Fe0.5VO4 was compared with those of other catalysts. Ce0.5Fe0.5VO4 is more active than Ce0.5Fe0.5Ox reported in our previous work [27] because Ce0.5Fe0.5Ox can only achieve about 70% NOx conversion at 300 °C under relatively milder conditions (200 mg catalyst, [NO] = 500 ppm, flow rate = 500 mL/min) [27], whereas Ce0.5Fe0.5VO4 can achieve 75.3% NOx conversion at 300 °C under relatively harsher conditions (200 mg catalyst, [NO] = 500 ppm, flow rate = 1000 mL/min). For comparison, Fe0.3Ce0.7VO4 developed by Zhang and co-workers can lead to >95% NOx conversion at 250–300 °C under relatively milder conditions (300 mg catalyst, [NO] = 500 ppm, flow rate = 250 mL/min) [14]. In a recent work by Tang and co-workers, Ce-W/TiO2 can leads to ~90% NO conversion at 300 °C under conditions identical to those in our current work (200 mg catalyst, [NO] = 500 ppm, flow rate = 1000 mL/min) [29].

2.2. Regular Characterization

Figure 2 gives the XRD patterns of samples. CeVO4 shows peaks at 2θ = 18.4, 24.3, 32.7, 34.6, 39.3, 43.8, 48.2, and 55.9°, attributed to the (101), (200), (112), (220), (301), (103), (312), and (420) planes of tetragonal CeVO4, respectively [30]. The other minor peaks are all consistent well with the standard pattern of CeVO4 (JCPDS: 12-0757). The XRD patterns of FeVO4 shows characteristic peaks at 25.2, 27.1, 27.8, 28.0, 42.1, 42.2, 49.8, 52.4, 54.8 and 59.2°, are ascribed to the (012),   ( 2 ¯ 01),   ( 1 1 ¯ 2), ( 2 ¯ 10), ( 3 ¯ 10), ( 0 3 ¯ 3), (123), ( 3 1 ¯ 2), ( 4 ¯ 12) and   ( 2 2 ¯ 3) lattice planes of triclinic FeVO4 (JCPDS: 71-1592) [31]. The XRD patterns of Ce0.75Fe0.25VO4, Ce0.5Fe0.5VO4, and Ce0.25Fe0.75VO4 are similar to that of CeVO4, indicating that the former samples keep the structure of CeVO4.
The magnified (200) peak of CeVO4, Ce0.75Fe0.25VO4, Ce0.5Fe0.5VO4, and Ce0.35Fe0.75VO4 are manifested in Figure S3 from Supplementary Materials. It is clear to see that the 2θ value right shifts to the lager value with the increase in Fe content, because the ion radius of the doped Fe3+ (49 pm) is much smaller than that of Ce3+ (103.8 pm) [32,33]. According to the Bragg’s law, 2d(hkl)sinθ = nλ, the increase of 2θ value corresponds to the decrease in the d spacing d(hkl) value, that is, lattice constraint. This fact implies that the Fe3+ ions substitute some Ce4+ sites. With the increase in Fe contents, the crystal parameter “a” gradually decreases from 0.7399 to 0.7349 nm, while the crystal parameter “c” gradually decreases from 6.496 to 6.469 nm (Table S1 in Supplementary Materials). Once the Fe3+ ions are doped into the crystal cell, the cell volume will shrink.
Figure 3 shows the SEM images of samples. The sizes of CeVO4 crystals are a few-hundred nanometers, and CeVO4 is composed of irregular particles, rods, and plates. The sizes of FeVO4 crystals are also a few hundred nanometers, and FeVO4 is composed of agglomerated particles. Ce0.75Fe0.25VO4, Ce0.50Fe0.50VO4, and Ce0.25Fe0.75VO4 generally exhibit morphologies more similar to that of CeVO4.
HRTEM image of CeVO4 is illustrated in Figure 4a. The (200) interplanar spacing is 0.369 nm, equal to that of un-doped CeVO4 (0.369 nm) [34]. The (101) interplanar spacing is 0.484 nm, identical to that of un-doped CeVO4 (0.487 nm) [19,34]. The angle between the (101) and (200) planes (90°) further confirms that the prepared sample is CeVO4. Figure 4b illustrates the HRTEM image of Ce0.50Fe0.50VO4. The d spacing of the (101) plane is 0.482 nm, slightly smaller than that of CeVO4 (0.484 nm). The d spacing of the (200) plane is 0.367 nm, also slightly smaller than that of CeVO4 (0.369 nm). The reason is that the ionic radius of Fe3+ (49 pm) is smaller than that of Ce3+ (103.8 pm) [32,33]. It is noticeable that the angle between the (101) and (200) planes (101°) is obviously larger than that of CeVO4 (90°). These results mean that some Fe3+ substitute the Ce4+ and slightly changes the parameters of crystal cells.
The EDX-mapping data Ce0.50Fe0.50VO4 (Figure 5) show the even distribution of Ce, Fe, V, and O elements. XRF data show that the Ce: Fe: V molar ratio of Ce0.50Fe0.50VO4 is 0.507:0.493:1, close to the theoretical ratio.

2.3. XPS Data

Figure 6 gives the Ce 3d XPS spectra. The Ce 3d3/2 and Ce 3d5/2 signals are marked as “u” and “v”, respectively. The v, v″, v‴, u, u″, and u‴ can be ascribed to surface Ce4+, whereas v′ and u′ can be attributed to surface Ce3+. The surface Ce3+/(Ce4+ + Ce3+) ratio of CeVO4 is 39.1%, corresponding to an average oxidation state (AOS) of 3.61 (for Ce). For comparison, the surface Ce3+/(Ce4+ + Ce3+) ratio of Ce0.50Fe0.50VO4 is 23.2%, corresponding to an AOS of 3.77.
Figure 7 illustrates the Fe 2p XPS spectra. The surface Fe2+/(Fe2+ + Fe3+) ratio of FeVO4 is 29.9%, corresponding to an AOS of 2.70 (for Fe). On the other hand, the Fe2+/(Fe2+ + Fe3+) ratio of Ce0.50Fe0.50VO4 is 28.1%, corresponding to an AOS of 2.72.
Figure 8 shows the V 2p XPS spectra. The surface V4+/(V4+ + V5+) ratio of Ce0.50Fe0.50VO4 is 24.2%, while those of CeVO4 and FeVO4 are 18.7% and 18.9%, respectively, which means the AOSs of V in Ce0.50Fe0.50VO4, CeVO4, and FeVO4 are 4.76, 4.81, 4.81, respectively. The above results manifest that when some Fe3+ replace Ce4+, the oxidation states of Fe, Ce, and V are all changed.
Figure 9 shows the O 1s XPS spectra. The O 1s spectra can be divided into two peaks at 529.9, and 531.1 eV corresponding to lattice oxygen (denoted as Oα) as well as the surface oxygen and oxygen vacancies (denoted as Oβ), respectively [19,35]. Owing to greater mobility, Oβ (surface labile oxygen) is more active compared to Oα (bulk oxygen). As shown in Figure 9, Ce0.5Fe0.5VO4 has the highest concentration of surface labile oxygen species among three representative catalysts.

2.4. H2-TPR and NH3-TPD Data

Figure 10 shows the H2-TPR profiles of samples. CeVO4 exhibits a peak at 864 °C, corresponding to the reduction of CeVO4 to CeVO3 [24,36]. In the H2-TPR profile of FeVO4, the obvious peak around 648 °C is assigned to the reduction of VO43− [37], while the H2 consumption at lower temperatures is ascribed to the reduction of Fe3+ [16,37]. The first peak of Ce0.50Fe0.50VO4 at 550 °C is ascribed to the reduction of active surface oxygen. The second peak at 632 °C may be ascribed to the reduction of Fe3+ or Ce4+. The third peak at 740 °C is ascribed to the reduction of VO43− [15,24]. The data show that Ce0.5Fe0.5VO4 owns more surface oxygen useful for NH3-SCR.
Figure 11 shows the baseline-corrected NH3-TPD data obtained by subtracting the “blank” TPD profile. The four peaks in low, medium, high, and superhigh temperature regions are ascribed to weak, medium, medium strong, and strong acid sites, as divided by peakfit V4.12 software. The distribution of four kinds of acid sites can be estimated by the relative peak areas. It is observed that the Fe0.50Ce0.50VO4 has more acid sites than CeVO4 and FeVO4, which may be beneficial for NH3 adsorption and NH3-SCR [24].

3. Materials and Methods

3.1. Synthesis

Ce1−xFexVO4 catalysts were synthesized by a modified sol-gel hydrothermal method. In a typical synthesis, 5 mmol NH4VO3 was added in 80 mL hot water and heated at 60 °C in a water bath with constant stirring to prepare solution A. Stoichiometric Fe(NO3)3·9H2O (98.5% purity, Sinopharm, Shanghai, China), Ce(NO3)3·6H2O (99.95%, Aladdin, Beijing, China), and 5 mmol citric acid were separately dissolved in 30 mL ethanol and then these three solutions (about 30 mL each) were mixed and magnetically stirred to form solution B. After 30 min of constant stirring plus heating in a water bath at 60 °C, the solution’s color turned from yellowish to transparent and clean. Solution B was added into solution A drop by drop, while the whole solution was stirred vigorously. Subsequently, a moderate amount of propylene oxide was added dropwise into the mixed solution heated in a water bath at 60 °C until a duck-blood-like sol solution was formed. Finally, 2 M NH3·H2O or 2 M HCl solution was added slowly into the above mixture with constant stirring. The final pH value of the sol solution, monitored by a pH meter, was 7. The sol solution was transferred to two sealed autoclaves (with 100 mL volume each) and hydrothermally treated at 180 °C for 24 h. Then, the solids in the autoclaves were isolated via filtration and washed with deionized water until the pH value of the solvent became 7. The solids were collected and dried at 110 °C for 6 h. The dried solids were carefully grinded in a mortar and transferred into a porcelain bowl and heated to 750 °C (heating rate: 5 °C/min) in a muffle oven (with static air), and then heated at 750 °C for 12 h.

3.2. Activity Measurement

Catalytic activity measurement was performed in a quartz tube reactor (i.d. = 8 mm). The 200 mg catalyst (40–60 mesh) was added in the reactor for each test. The feed gas contained NO (500 ppm), NH3 (500 ppm), O2 (3.0%), and balance N2. The total flow rate was 1000 mL/min. The gas concentrations were measured by an NO–NO2–NOx analyzer (42i-HL, High Level, Thermo Electron Corporation, Waltham, MA, USA).
NOx conversion was calculated using the given equation:
X NO x ( % ) = NO x in NO x out NO x in × 100 %
where [NOx]in and [NOx]out are the concentrating of NOx entering the reactor and exiting the reactor, respectively.

3.3. Characterization

XRD patterns were recorded on an Advanced D8 (Bruker) powder diffractometer using Cu Kα radiation. TEM images were obtained with a JEOL JEM-2100F field emission TEM instrument equipped with an EDAX Genesis XM4-Sys60 system (EDAX Inc., Mahwah, NJ, USA). The elemental compositions of powders were determined by XRF (Thermo-3600, Thermo Fisher Scientific Inc., Waltham, MA, USA). The specific BET surface data were measured using a Micromeritics analyzer (Tristar II 3020M, Micromeritics, Norcross, GA, USA). XPS data were obtained on a thermoESCLAB 250XI instrument using monochromatic Al Kα radiation (Thermo, Waltham, MA, USA).
H2-TPR experiments were carried out using a Micromeritics AutoChem 2920 (Micromeritics, Norcross, GA, USA) chemisorption instrument, following the procedure reported [38,39]. Firstly, the sample (40–60 mesh, 100 mg) was placed in a quartz tube reactor. Secondly, the sample was pretreated at 300 °C in 20 vol.% O2/Ar (50 mL/min) for 0.5 h and cooled down to 30 °C followed by purging by Ar for 0.5 h. Then, a gas flow (10% H2 in Ar, 50 mL/min) passed through the sample. Finally, the temperature was increased from 50 to 950 °C at a rate of 10 °C min−1.
NH3-TPD experiments were carried out on a Micromeritics AutoChem 2920 chemisorption instrument. A sample (40–60 mesh, 50 mg), placed in a quartz reactor, was pretreated at 300 °C in 20 vol.% O2/Ar (50 mL/min) for 0.5 h and cooled down to 30 °C followed by Ar purging for 0.5 h. Then, 10% NH3 in Ar (50 mL/min) flowed through the sample, and the temperature was ramped from 50 to 650 °C at a rate of 10 °C min−1.

4. Conclusions

A series of Ce1−xFexVO4 catalysts were prepared by a modified hydrothermal method. It was found that that Ce0.50Fe0.50VO4 exhibits the optimum NOx conversion efficiency compared with other catalysts. With the incorporation of Fe3+, the crystal structure of CeVO4 crystal gradually distorts and the average oxidation states of Ce, Fe, and V change accordingly. The surface oxygen and oxygen vacancy contents increase, as proved by XPS and H2-TPR data. Ce0.50Fe0.50VO4 has more weak and medium acid sites compared with CeVO4 and FeVO4. These factors contribute to the enhanced catalytic performance of Ce0.50Fe0.50VO4. The anti-SO2 and anti-H2O performance of NH3-SCR catalysts should be studied in the future for applications under realistic environments.

Supplementary Materials

The following supporting information can be downloaded at: https://0-www-mdpi-com.brum.beds.ac.uk/article/10.3390/catal12050549/s1, Table S1. The crystallographic data of Ce1−xFexVO4 samples, some of which were obtained using the Rietveld refinements. Figure S1. XNOx over Ce1−xFexVO4 catalysts prepared by a hydrothermal method. Reaction conditions: [NO] = 500 ppm, [NH3] = 500 ppm, [O2] = 3 vol.%, balance N2; catalyst weight: 200 mg; total flow rate: 1000 mL·min−1. Figure S2. XNOx over Ce0.5Fe0.5VO4 at 300 °C as a function of time on stream. Reaction conditions: [NO] = 500 ppm, [NH3] = 500 ppm, [O2] = 3 vol.%, balance N2; catalyst weight: 200 mg; total flow rate: 1000 mL·min−1. Figure S3. XRD patterns (2θ = 22–27°) of Ce1−xFexVO4 catalysts.

Author Contributions

Conceptualization, J.W.; Data curation, J.W. and X.Z.; Formal analysis, L.W. and H.C.; Investigation, L.W. and X.Z.; Supervision, Z.M.; Writing—original draft, L.W. and J.W.; Writing—review and editing, Z.M. All authors have read and agreed to the published version of the manuscript.

Funding

This work was financially supported by the Natural Science Research Key Project of Anhui Provincial Department of Education (KJ2021A1036), Natural Science Foundation of Zhejiang province (Y5090310, LY19E080023), Natural Science Foundation of Anhui province (KJ2018A0406), the Open Foundation of State Key Laboratory of Precision Spectroscopy (East China Normal University), Excellent and top-notch talent cultivation funding project in Anhui universities (GXFX2017106), and Special Fund for the Construction of Innovative Provinces (2020XZX005).

Data Availability Statement

Data are available from the authors.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. XNOx over Ce1−xFexVO4 catalysts prepared by a hydrothermal method. Reaction conditions: [NO] = 500 ppm, [NH3] = 500 ppm, [O2] = 3 vol.%, balance N2; catalyst weight: 200 mg; total flow rate: 1000 mL·min−1.
Figure 1. XNOx over Ce1−xFexVO4 catalysts prepared by a hydrothermal method. Reaction conditions: [NO] = 500 ppm, [NH3] = 500 ppm, [O2] = 3 vol.%, balance N2; catalyst weight: 200 mg; total flow rate: 1000 mL·min−1.
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Figure 2. XRD patterns of Ce1−xFexVO4 catalysts.
Figure 2. XRD patterns of Ce1−xFexVO4 catalysts.
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Figure 3. SEM images of Ce1−xFexVO4. (a) CeVO4; (b) Ce0.75Fe0.25VO4; (c) Ce0.50Fe0.50VO4; (d) Ce0.25Fe0.75VO4; (e) FeVO4.
Figure 3. SEM images of Ce1−xFexVO4. (a) CeVO4; (b) Ce0.75Fe0.25VO4; (c) Ce0.50Fe0.50VO4; (d) Ce0.25Fe0.75VO4; (e) FeVO4.
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Figure 4. The HRTEM images of CeVO4 (a) and Ce0.50Fe0.50VO4 (b).
Figure 4. The HRTEM images of CeVO4 (a) and Ce0.50Fe0.50VO4 (b).
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Figure 5. SEM image (a) and the corresponding EDX mapping images of O (b), Ce (c), Fe (d) and V (e) elements of Ce0.50Fe0.50VO4. The scale bar represents 20 μm.
Figure 5. SEM image (a) and the corresponding EDX mapping images of O (b), Ce (c), Fe (d) and V (e) elements of Ce0.50Fe0.50VO4. The scale bar represents 20 μm.
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Figure 6. Ce 3d XPS spectra of CeVO4 and Ce0.50Fe0.50VO4.
Figure 6. Ce 3d XPS spectra of CeVO4 and Ce0.50Fe0.50VO4.
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Figure 7. Fe 2p XPS spectra of CeVO4 and Ce0.50Fe0.50VO4.
Figure 7. Fe 2p XPS spectra of CeVO4 and Ce0.50Fe0.50VO4.
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Figure 8. V 2p XPS spectra of CeVO4, Ce0.50Fe0.50VO4, and FeVO4.
Figure 8. V 2p XPS spectra of CeVO4, Ce0.50Fe0.50VO4, and FeVO4.
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Figure 9. O 1s XPS spectra of CeVO4, Ce0.50Fe0.50VO4, and FeVO4.
Figure 9. O 1s XPS spectra of CeVO4, Ce0.50Fe0.50VO4, and FeVO4.
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Figure 10. H2-TPR profiles of the catalysts.
Figure 10. H2-TPR profiles of the catalysts.
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Figure 11. NH3-TPD profiles of the catalysts.
Figure 11. NH3-TPD profiles of the catalysts.
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Wang, L.; Wang, J.; Cheng, H.; Zhou, X.; Ma, Z. Ce1−xFexVO4 with Improved Activity for Catalytic Reduction of NO with NH3. Catalysts 2022, 12, 549. https://0-doi-org.brum.beds.ac.uk/10.3390/catal12050549

AMA Style

Wang L, Wang J, Cheng H, Zhou X, Ma Z. Ce1−xFexVO4 with Improved Activity for Catalytic Reduction of NO with NH3. Catalysts. 2022; 12(5):549. https://0-doi-org.brum.beds.ac.uk/10.3390/catal12050549

Chicago/Turabian Style

Wang, Li, Junbo Wang, Heping Cheng, Xiangxiang Zhou, and Zhen Ma. 2022. "Ce1−xFexVO4 with Improved Activity for Catalytic Reduction of NO with NH3" Catalysts 12, no. 5: 549. https://0-doi-org.brum.beds.ac.uk/10.3390/catal12050549

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