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Article

Effects of the Doping of La and Ce in the Pt/B-TiO2 Catalyst in Selective Oxidation Reaction of Glycerol

by
Zhihui Wang
,
Xueqiong Zhang
,
Bo Hai
,
Hao Zhang
and
Lijun Ding
*
Key Laboratory of the Development and Resource Utilization of Biological Pesticide in Inner Mongolia, College of Science, Inner Mongolia Agricultural University, Hohhot 010018, China
*
Author to whom correspondence should be addressed.
Crystals 2025, 15(4), 301; https://doi.org/10.3390/cryst15040301
Submission received: 21 February 2025 / Revised: 21 March 2025 / Accepted: 22 March 2025 / Published: 25 March 2025
(This article belongs to the Special Issue Advances and Perspectives in Noble Metal Nanoparticles)
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Abstract

:
The increased production of biodiesel results in a corresponding rise in the production of glycerol (GLY) as a by-product. The selective oxidation of glycerol can yield relatively simple products under mild reaction conditions, offering high added value and positioning it as one of the most promising methods for industrialization. In this study, we employed black titanium dioxide (B-TiO2) as a support and deposited platinum (Pt) to create a noble metal-supported catalyst. Lanthanum (La) or cerium (Ce) was doped into B-TiO2 to enhance the concentration of oxygen vacancies in the support, thereby improving catalyst activity. Throughout the research process, we also investigated the impact of varying amounts of La or Ce doping on catalyst performance. Analysis of the catalytic experimental data revealed that Pt/30%Ce-B-TiO2 exhibited the highest catalytic performance. Structural analysis of the catalysts showed that the synergistic effect between Pt0 and oxygen vacancies contributed to enhancing catalyst activity.

Graphical Abstract

1. Introduction

In the field of modern catalytic science, the development of efficient catalysts is essential for promoting the sustainable advancement of the chemical industry. In recent years, the glycerol oxidation reaction has garnered significant attention as a crucial process for converting glycerol, a by-product of biodiesel production, into high-value-added products [1,2]. Traditional catalysts often face challenges such as low conversion rates, poor selectivity, and insufficient stability during glycerol oxidation reactions, prompting researchers to continuously explore new types of catalytic materials [3,4,5]. Titanium dioxide (TiO2) has gained considerable interest due to its excellent chemical and thermal stability and is commonly utilized as a support material for catalysts. However, the catalytic activity of current TiO2-supported materials still requires enhancement [6]. As research progresses, the doping of rare earth elements into support materials has emerged as an effective strategy to improve catalytic activity, addressing the performance limitations of traditional catalysts while meeting growing industrial demands and environmental challenges. The unique electron layer structure and variable oxidation states of rare earth elements allow for the introduction of new active sites and electron transfer pathways into various catalytic materials, thereby significantly enhancing catalyst performance [7,8,9]. In thermal catalytic reactions, the advantages of doping with rare earth elements are particularly pronounced. For instance, in the methane reforming reaction, Ce-doped Ni-based catalysts demonstrate enhanced resistance to carbon deposits and exhibit higher catalytic activity. This improvement is attributed to the electron modification of Ni active sites by Ce, as well as the enhanced adsorption of reactants. The optimization of desorption behavior allows the reaction to proceed under milder conditions, thereby effectively improving both reaction efficiency and catalyst stability [10,11,12,13]. Cheng et al. utilized Ce-doped Ni(OH)2/Ni-MOF nanosheets as efficient catalysts for oxygen evolution reactions, revealing excellent catalytic performance [14]. Concurrently, the La-doped Co3O4 catalyst showcases remarkable low-temperature activity in oxidation reactions. By altering the concentration of surface oxygen species and the mobility of lattice oxygen within the catalyst, the activation energy of the reaction is reduced, which accelerates the reaction rate and enhances the purification of harmful gases [15,16].
Furthermore, the amount of rare earth element doping is critical for regulating catalyst performance. Variations in doping levels can lead to changes in the crystal structure, electron density, and surface properties of the catalyst, which subsequently affect the activity and selectivity of the catalytic reaction [17]. For example, adjusting the doping amount of Fe2+ can significantly enhance the electron conductivity of NiFe oxide, promoting the oxidation reaction of urea [18]. Rare earth element doping provides an effective means to enhance the catalytic performance of TiO2. Due to their unique electronic structure, rare earth elements possess f-orbital electrons that can interact with the TiO2 lattice, thereby modulating both the electronic and surface chemical properties of the catalyst [19,20,21,22,23]. By doping with rare earth elements, additional active sites can be introduced, optimizing the adsorption and activation processes of reactants, which in turn improves catalytic activity and selectivity [24,25,26]. Furthermore, the preparation of black TiO2 typically involves the creation of oxygen vacancies, which can enhance electron transfer capacity and further boost catalytic activity. The support material for the catalyst significantly influences its activity, selectivity, and stability. Lanthanum (La) or Cerium (Ce)-doped black TiO2 is expected to exhibit exceptional properties in the glycerol selective oxidation reaction. On the one hand, rare earth element doping can enhance the redox performance of the catalyst, leading to improved catalytic activity and selectivity during thermal catalysis. On the other hand, the presence of oxygen vacancies in black titanium dioxide facilitates better interaction between the reactants and the catalyst, thereby promoting the reaction progress [27,28,29,30].
This study aims to investigate the performance of La and Ce-doped black TiO2 in the thermal catalytic reaction of glycerol oxidation. By examining the types and doping ratios of the doped elements, the catalyst exhibiting the best performance is identified. Characterization techniques such as XRD and XPS are employed to study the intrinsic relationship between catalyst structure and performance, thereby elucidating the catalytic action mechanism. The findings of this study provide an experimental foundation for the development of highly efficient alkali-free thermal catalytic materials for thermal oxidation reactions. Furthermore, it promotes advancements in biomass conversion and offers new insights into the application of rare earth element doped oxide catalysts in thermal catalytic reactions.

2. Materials and Methods

2.1. Reagents

Tetrabutyl titanate (C16H36O4Ti, A.R) from Shanghai Lin’en Technology Development Co., Ltd. (Shanghai, China); Glycerol (C3H8O, A.R) from Tianjin Fengchuan Chemical Reagent Technology Co., Ltd. (Tianjin, China); 3 wt% Hydrofluoric acid (HF, A.R) from Shanghai Adamas Reagent Co., Ltd. (Shanghai, China); Absolute ethanol (C2H6O, A.R) from Tianjin New Technology Industrial Park Kemao Chemical Reagent Co., Ltd. (Tianjin, China); Potassium chloroplatinate (K2PtCl6, 99.95%) from Shanghai Adamas Reagent Co., Ltd. (Shanghai, China); Sodium borohydride (NaBH4, 99.8%) from Shanghai Adamas Reagent Co., Ltd. (Shanghai, China); Cerium nitrate (Ce(NO3)3·6H2O, A.R) from Shanghai Adamas Reagent Co., Ltd. (Shanghai, China); Lanthanum nitrate (La(NO3)3·6H2O, A.R) from Shanghai Adamas Reagent Co., Ltd. (Shanghai, China).

2.2. Preparation of La-B-TiO2 and Ce-B-TiO2

The hydrothermal synthesis method is employed to prepare La and Ce-doped B-TiO2 precursors with varying doping amounts. The specific synthesis procedure is as follows: La(NO3)3·6H2O or Ce(NO3)3·6H2O is added to tetrabutyl titanate (C16H36O4Ti, A.R), with doping amounts of 1%, 4%, 7%, 10%, 20%, 30%, and 50% (the specific values are calculated based on the total doping amount). The mixture is stirred and transferred to a hydrothermal reactor, which is then placed in an oven at 180 °C for 24 h. Afterward, the resulting product is washed three times with deionized water and absolute ethanol using centrifugal methods and subsequently transferred to an oven at 60 °C for 6 h. The dried sample is then placed in a muffle furnace, where the temperature is increased to 500 °C at a heating rate of 10 °C/min and maintained for 3 h. Finally, the calcined sample is moved to a tube furnace, where a hydrogen-to-argon volume ratio of 2:3 is maintained, the temperature is raised to 600 °C at a rate of 10 °C/min and held for 4 h to obtain the La-B-TiO2 and Ce-B-TiO2.

2.3. Preparation of Pt/La-B-TiO2 and Pt/Ce-B-TiO2

Pt/La-B-TiO2 and Pt/Ce-B-TiO2: Weigh 0.4275 g of the Pt/La-B-TiO2 or Pt/Ce-B-TiO2 support and place it into a 100 mL round-bottom flask. Add 60 mL of absolute ethanol, then disperse the mixture and stir for 30 min. Subsequently, introduce 6 mL of K2PtCl6 aqueous solution, with a concentration of 10 mg/mL (corresponding to a Pt loading of 5%), into the carrier dispersion. Next, weigh 0.01 g of NaBH4 and dissolve it in cold water, which occurs rapidly. Quickly add the dissolved NaBH4 solution into the flask, adjusting the stirring speed to stir vigorously for 3 h. Afterward, centrifuge the mixture and wash it three times with deionized water and absolute ethanol. Finally, the obtained product is transferred to an oven and maintained at a temperature of 80 °C for 6 h to yield Pt/La-B-TiO2 or Pt/Ce-B-TiO2 catalyst.

2.4. Material Characterization

The X-ray powder diffraction (XRD, TD-3700) was conducted using monochromatic Cu Kα1 radiation (λ = 0.15405 nm) operated at power (35 kV, 25 mA). Quantitative diffraction data analysis was conducted using Jade 9 software. The detection range spans from 5° to 80°, with a scanning speed of 5°/min and a wavelength of 0.15406 nm.
The sizes and morphologies of Pt/4%La-B-TiO2 or Pt/30%Ce-B-TiO2 were examined by scanning electron microscope (SEM, S-4800, Hitachi, Tokyo, Japan) at an acceleration voltage of 20 kV. Following ultrasonic dispersion in ethanol, the samples were deposited onto the surface of a silicon wafer. Subsequent to the evaporation of the ethanol, the samples were examined, and mapping tests were performed to obtain and analyze their elemental content.
X-ray photoelectron spectroscopy (XPS, ESCALAB 250, Thermo Fisher Scientific Inc., Waltham, MA, USA) of Pt/30%Ce-B-TiO2, Pt/50%Ce-B-TiO2 and Pt/4%La-B-TiO2 was conducted using a monochromatic X-ray excitation source of Al anode Kα radiation (1486.6 eV). The binding energies were calibrated to the C 1s peak of carbon at 284.6 eV prior to the actual measurements.
N2 adsorption-desorption measurements of 4%La-B-TiO2 and 30%Ce-B-TiO2 were conducted using BSD-PS2. The Brunauer–Emmett–Teller (BET) method was used to estimate the specific surface areas.
The products of the selective oxidation reaction of glycerol were analyzed using high-performance liquid chromatography (HPLC, Agilent 1260 Infinity, Santa Clara, CA, USA), equipped with an Alltech OA-1000 organic acid column, a refractive index detector (RID) operating at 35 °C, and a diode array detector (DAD) set to λ = 210 nm. The mobile phase consisted of 5 mM H2SO4 aqueous solution with a flow rate of 0.5 mL/min. A 20 µL sample was injected into the column, which was maintained at a temperature of 80 °C.

3. Results

3.1. Characterization of the Materials

Figure 1 presents the X-ray diffraction (XRD) diagrams of Ce-B-TiO2 (Figure 1a and Figure 1b) and La-B-TiO2 (Figure 1c and Figure 1d), respectively, illustrating the effects of varying doping quantities. The characteristic TiO2 peaks were observed at 25.3°, 37.8°, 48.0°, 53.9°, and 55.1°, corresponding to the anatase titanium dioxide (TiO2) crystal planes (101), (004), (200), (105), and (211). Notably, the peak positions for TiO2 in Ce-B-TiO2 and La-B-TiO2 remain unchanged, suggesting that the doping of Ce and La does not alter the TiO2 structure, thereby confirming the successful incorporation of Ce and La. The standard cards for CeF3 and LaF3 are also presented in Figure 1. In Figure 1a,b, the diffraction peaks of Ce-B-TiO2 not only align with the peak positions of anatase TiO2 but also exhibit characteristic peaks at 27.9°and 45.3°. As the amount of Ce doping increases, the intensity of this diffraction peak also rises, corresponding to the characteristic peak of CeF3. Similarly, in Figure 1c,d, as the doping amount of La increases, the intensity of the diffraction peaks for La-B-TiO2 increases at 27.6°and 45.2°, corresponding to the characteristic peak of LaF3. The presence of CeF3 and LaF3 during the synthesis of Ce-B-TiO2 and La-B-TiO2 can be attributed to the addition of HF [31,32,33].
Figure 2 and Figure 3 illustrate the SEM-mapping of Pt/4%La-B-TiO2 and Pt/30%Ce-B-TiO2, respectively. The carriers of Pt/4%La-B-TiO2 (Figure 2a) and Pt/30%Ce-B-TiO2 (Figure 3a) exhibit a skeletal morphology characterized by a large specific surface area [34,35,36,37,38]. The BET test results for the two supports, 4%La-B-TiO2 and 30%Ce-B-TiO2, are presented in Figure S2, with the data detailed in Table S1. The test data indicate that the specific surface area of 4%La-B-TiO2 (30.13 m2/g) is greater than that of 30%Ce-B-TiO2 (17.96 m2/g). The pore volumes of both supports are comparable, each measuring approximately 0.25 cm3/g. Additionally, the average pore diameter of 30%Ce-B-TiO2 (53.41 nm) exceeds that of 4%La-B-TiO2 (39.60 nm). Figure 2b and Figure 2c show the EDS element distribution of titanium (Ti) and oxygen (O) elements on the 4%La-B-TiO2 support, revealing a relatively uniform distribution of both elements across the surface. Figure 2d depicts the distribution of the lanthanum (La) element, which is found to be concentrated more at the edges of the support. This may be attributed to the low doping amount of La, resulting in its preferential distribution at the edges. Figure 2e indicates that the distribution of platinum (Pt) elements on the support is relatively uniform. Figure 3a presents the SEM image of Pt/30%Ce-B-TiO2. Subsequently, we examined the elemental distribution within the green boxed area of the image, which predominantly includes Ti, O, Ce, and Pt. Figure 3b and Figure 3c demonstrate that the EDS element distribution of Ti and O elements on the 30%Ce-B-TiO2 support are also relatively uniform. Figure 3d presents the distribution of cerium (Ce) element, which is more abundant compared to the doping amount of La. This is clearly illustrated in Figure 3d, highlighting the greater doping amount of Ce. Finally, Figure 3e shows that Pt is uniformly distributed on the support.

3.2. Selective Oxidation Reaction of Glycerol

The activity of the catalyst was evaluated through the glycerol oxidation reaction. Table S2 presents the activity data for the undoped catalyst. Conversion data collected over a period of 6 h indicated that the catalyst exhibited the highest conversion when the reduction temperature of B-TiO2 was set to 700 °C. For subsequent doping experiments, Pt/B-TiO2 (700 °C) served as the base material, while the carrier B-TiO2 (700 °C) was doped with rare earth elements, specifically La and Ce.
Figure 4a illustrates the variation in the catalytic conversion of the Pt/Ce-B-TiO2 catalyst over time at different doping ratios of Ce. During the initial two hours of the reaction, the conversion rates for catalysts with Ce doping ratios of 1%, 10%, and 15% were low. In contrast, the catalytic activity for the 20% doping ratio was moderate, while the Pt/30%Ce-B-TiO2 and Pt/50%Ce-B-TiO2 catalysts exhibited high catalytic activity. After two hours, the conversion rate reached 40%. By 6 h, the conversion rates for Pt/30%Ce-B-TiO2 and Pt/50%Ce-B-TiO2 were 87.10% and 77.82%, respectively (see Table S2). Figure 4b illustrates the selectivity changes of the Pt/Ce-B-TiO2 catalyst for glyceric acid over time at various doping ratios. The data indicate that the selectivity for glyceric acid remains consistent across all six doping ratios, with an increasing trend over time. Notably, the catalysts Pt/30%Ce-B-TiO2 and Pt/50%Ce-B-TiO2 exhibited particularly strong performance. After 4 h of reaction, Pt/50%Ce-B-TiO2 achieved the highest selectivity for glyceric acid at 62%. However, at this point, its conversion rate (77.82%) was lower than that of Pt/30%Ce-B-TiO2 (87.10%). From a yield perspective (see Figure 4c), the activity of catalysts can be assessed after 6 h, with Pt/30%Ce-B-TiO2 achieving the highest yield at 52.87%. The catalytic data presented in Table S2 demonstrate that the activity and selectivity for glyceric acid are enhanced in the doped catalysts compared to the undoped Pt/B-TiO2 (700 °C). Over the 6 h reaction period, Pt/30%Ce-B-TiO2 exhibited a 20% increase in conversion rate and a 25% increase in glyceric acid selectivity compared to Pt/B-TiO2. In summary, the catalyst Pt/30%Ce-B-TiO2 displays the highest catalytic performance.
Figure 4d illustrates the variation in catalytic activity across different doping ratios of La in the Pt/La-B-TiO2 catalyst, with the La doping amount controlled between 1% and 20%. In comparison to the catalytic activity of the Pt/La-B-TiO2 catalyst depicted in Figure 4a, the overall catalytic activity of the Pt/Ce-B-TiO2 catalysts is relatively low. Notably, Pt/4%La-B-TiO2 exhibited the highest catalytic activity after 6 h, achieving a value of 55.05%. However, when compared to the catalytic performance (22.71%) of the undoped Pt/B-TiO2 at 700 °C, the catalytic performance (31.86%) of Pt/4%La-B-TiO2 did not show a significant improvement. This suggests that the doping of La has a limited effect on the activity of the Pt/B-TiO2 structural catalyst. Figure S1 illustrates the change in glyceric acid selectivity of the Pt/La-B-TiO2 catalyst over time, while Table S2 presents the data for selectivity of glyceric acid by Pt/La-B-TiO2 after 6 h. The observed trends and data indicate that the doping of La has a significant regulatory effect on the selectivity of the Pt/B-TiO2 catalyst. As the amount of La doping increases, there is a discernible trend towards enhanced selectivity for glyceric acid in the Pt/La-B-TiO2 catalyst. The experimental data suggest that the optimal doping ratio is 4%. Furthermore, when considering the conversion data, it is evident that the yield of Pt/4%La-B-TiO2 after 6 h of reaction is 31.86%. This represents an improvement in yield compared to the undoped Pt/B-TiO2 (700 °C).
Table S3 presents the activities and selectivities of supported catalysts as reported in the literature [39,40,41,42,43,44,45,46,47]. A comparison reveals that the catalyst Pt/30%Ce-B-TiO2 synthesized in this study exhibits a relatively high conversion rate of 87.10% after 6 h under similar reaction conditions. The selectivity to glyceric acid at this conversion rate is moderate, and the yield is also at a moderate level. In contrast, the catalyst Pt/4%La-B-TiO2, also synthesized in this study, achieves a conversion rate of 55.05% after 6 h under similar reaction conditions, which is considered moderate. However, the selectivity to glyceric acid at this conversion rate is low, and the yield is likewise low. In conclusion, the catalyst developed in this study effectively enhances catalytic activity by doping the Ce element into the B-TiO2 support. Among the supported catalysts utilized in the current glycerol selective oxidation reaction, its performance stands out, offering a novel approach for the design of catalysts in glycerol selective oxidation reactions.

4. Discussion

To investigate the influence of the doping amounts of La and Ce on the catalyst structure of Pt/La-B-TiO2 and Pt/Ce-B-TiO2, as well as the impact of catalyst structure on catalytic performance, we conducted X-ray photoelectron spectroscopy (XPS) analysis. This analysis focused on the valence state and content of Pt and Ti in three catalysts: Pt/30%Ce-B-TiO2, Pt/50%Ce-B-TiO2, and Pt/4%La-B-TiO2 (Figure 5). The results indicate that the 4f spectrum of Pt in these catalysts comprises six peaks (Figure 5a–c), which correspond to three valence states: Pt0, Pt2+, and Pt4+. The Ti2p spectrum reveals four peaks (Figure 5d–f), with peaks at 458 eV and 464 eV attributed to Ti3+, while peaks at 459 eV and 465 eV correspond to Ti4+. The peak position data and content information for Ti3+ are summarized in Table S4. The doping of La and Ce has a significant effect on the valence state and content of Pt in the catalyst. The content of Pt0 in the catalyst Pt/La-B-TiO2 (Figure 5c) was higher than that in the catalyst Pt/Ce-B-TiO2 (Figure 5a,b), with the Pt/30%Ce-B-TiO2 exhibiting the highest Pt0 content (Table S5). In the selective oxidation reaction of glycerol, a reaction time of 6 h yields a conversion rate of 55.05% for the catalyst Pt/4%La-B-TiO2, with a selectivity for glyceric acid at 57.88% and a final yield of 31.86%. In comparison, the cerium-doped catalysts Pt/30%Ce-B-TiO2 and Pt/50%Ce-B-TiO2 exhibit conversion rates of 87.10% and 77.82%, respectively, surpassing that of Pt/4%La-B-TiO2. Notably, Pt/30%Ce-B-TiO2 demonstrates the selectivity for glyceric acid at 60.70%, while Pt/50%Ce-B-TiO2 shows the selectivity of 61.89%. Ultimately, among the three evaluated catalysts, Pt/30%Ce-B-TiO2 achieves the highest glyceric acid yield of 52.87%. The analysis results from X-ray photoelectron spectroscopy (XPS) indicate that Pt0 plays a crucial role in the catalytic reaction.
The Ti3+ content in the catalyst is calculated based on the ratio of Ti3+ to the sum of Ti3+ and Ti4+. The data presented in Table S4 indicate that Ti3+ constitutes 22.51% in Pt/4%La-B-TiO2, 26.60% in Pt/30%Ce-B-TiO2, and 30.06% in Pt/50%Ce-B-TiO2. This suggests that the doping of La and Ce does not significantly affect the Ti3+ content in the catalyst support. However, the amount of Ce in the Pt/Ce-B-TiO2 catalysts has a notable impact on the Ti3+ content, as evidenced by the observed data trends. Specifically, with an increase in Ce doping within the catalyst, the Ti3+ content also rises. Among the catalysts analyzed, Ti3+ represents the highest proportion in Pt/50%Ce-B-TiO2. Since the concentration of Ti3+ directly influences the concentration of oxygen vacancies in the catalyst support, it is essential to examine the oxygen vacancies concentration within the catalyst.
Figure 6 shows the deconvoluted XPS spectrum for O 1s in Pt/30%Ce-B-TiO2 (Figure 6a), Pt/50%Ce-B-TiO2 (Figure 6b) and Pt/4%La-B-TiO2 (Figure 6c). The main peak at 530.0 eV is assigned to the Ti4+-O bond in the TiO2 lattice, and it agrees well with the literature [48,49]. The peak with a position at 532 eV is mainly attributed to the oxygen from H2O [50]. The peak observed at a binding energy of 531.0 eV is attributed to the oxygen vacancy resulting from the presence of Ti3+ defects, with the area under the curve indicating the concentration of oxygen vacancies. Compared to La-B-TiO2, Ce-B-TiO2 exhibits a higher concentration of oxygen vacancies. Furthermore, a comparison of the oxygen vacancy concentrations in Pt/30%Ce-B-TiO2 and Pt/50%Ce-B-TiO2 reveals that the concentration of oxygen vacancies increases with higher levels of Ce doping, which correlates with the trend observed in Ti3+ content, as shown in Figure 5.

5. Conclusions

Based on the data analysis, the catalytic performance of the catalyst Pt/30%Ce-B-TiO2 exhibits the highest catalytic activity over a duration of 6 h, primarily attributed to the highest content of Pt0. In the initial 4 h, the catalytic activity of Pt/50%Ce-B-TiO2 is comparable to that of Pt/30%Ce-B-TiO2, likely due to the higher concentration of oxygen vacancies in Pt/50%Ce-B-TiO2. However, as the reaction progresses, the concentration of oxygen vacancies in the catalyst support diminishes, and the content of Pt0 also declines, resulting in lower catalytic activity compared to Pt/30%Ce-B-TiO2 at 6 h. Nevertheless, the selectivity for glyceric acid remains similar to that of Pt/30%Ce-B-TiO2, approximately 60%. These experimental observations indicate that both the content of Pt0 and the concentration of oxygen vacancies collectively influence the catalytic activity. Furthermore, the selectivity data reveal that the selectivity for glyceric acid is predominantly determined by the type of doping elements used. When the catalytic conversion rates are comparable, the selectivity of Pt/La-B-TiO2 for glyceric acid demonstrates greater stability.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/cryst15040301/s1, Figure S1: The selectivity of Pt/La-B-TiO2 with different La doping levels; Figure S2: The BET of 4%La-B-TiO2 and 30%Ce-B-TiO2; Table S1: BET-specific surface area, pore volume, and pore size of 30%Ce-B-TiO2 and 4%La-B-TiO2; Table S2: The performance of various catalysts in oxidation of glycerol to glyceric acid; Table S3: Reaction conditions, reaction temperature, catalytic conversion, glyceric acid selectivity, and yield of different catalysts. Table S4: The semiquantitative calculation of the content of Ti3+ based on XPS spectra of the different Ce or La doping ratios in Pt/Ce-B-TiO2 and Pt/La-B-TiO2 catalysts; Table S5: The semiquantitative calculation of the content of Pt0 based on XPS spectra of the different Ce or La doping ratios in Pt/Ce-B-TiO2 and Pt/La-B-TiO2 catalysts.

Author Contributions

Conceptualization, X.Z. and L.D.; methodology, Z.W. and X.Z.; software, Z.W. and X.Z.; validation, Z.W. and X.Z.; formal analysis, Z.W. and X.Z.; investigation, Z.W. and X.Z.; resources, Z.W.; data curation, Z.W.; writing—original draft preparation, Z.W.; writing—review and editing, Z.W. and X.Z.; visualization, Z.W., X.Z., B.H. and H.Z.; supervision, L.D.; project administration, X.Z. and L.D.; funding acquisition, X.Z. and L.D. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by several funding sources, including the Inner Mongolia Autonomous Region Natural Science Foundation (2021BS02012), the Inner Mongolia Autonomous Region Higher Education Research Project (NJZY17455), and the Inner Mongolia Agricultural University High-level Talent Plan (NDYB2020-9).

Data Availability Statement

The original contributions presented in the study are included in the article and Supplementary Material, further inquiries can be directed to the author (lxyzxq@imau.edu.cn).

Acknowledgments

This research acknowledge the funding provided by the Natural Science Foundation of Inner Mongolia Autonomous Region and the Department of Science and Technology of Inner Mongolia Autonomous Region. We also acknowledge for the testing support offered by the Key Laboratory of Biopesticide Development and Resource Utilization of Inner Mongolia.

Conflicts of Interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

References

  1. Dasari, M.A.; Kiatsimkul, P.-P.; Sutterlin, W.R.; Suppes, G.J. Low-Pressure Hydrogenolysis of Glycerol to Propylene Glycol. Appl. Catal. Gen. 2005, 281, 225–231. [Google Scholar] [CrossRef]
  2. Anitha, M.; Kamarudin, S.K.; Kofli, N.T. The Potential of Glycerol as a Value-Added Commodity. Chem. Eng. J. 2016, 295, 119–130. [Google Scholar] [CrossRef]
  3. Hu, X.; Lu, J.; Liu, Y.; Chen, L.; Zhang, X.; Wang, H. Sustainable Catalytic Oxidation of Glycerol: A Review. Environ. Chem. Lett. 2023, 21, 2825–2861. [Google Scholar] [CrossRef]
  4. Dodekatos, G.; Schünemann, S.; Tüysüz, H. Recent Advances in Thermo-, Photo-, and Electrocatalytic Glycerol Oxidation. ACS Catal. 2018, 8, 6301–6333. [Google Scholar] [CrossRef]
  5. Katryniok, B.; Kimura, H.; Skrzyńska, E.; Girardon, J.-S.; Fongarland, P.; Capron, M.; Ducoulombier, R.; Mimura, N.; Paul, S.; Dumeignil, F. Selective Catalytic Oxidation of Glycerol: Perspectives for High Value Chemicals. Green Chem. 2011, 13, 1960. [Google Scholar] [CrossRef]
  6. Fujishima, A.; Zhang, X.; Tryk, D. TiO2 Photocatalysis and Related Surface Phenomena. Surf. Sci. Rep. 2008, 63, 515–582. [Google Scholar] [CrossRef]
  7. Verma, V.; Singh, S.V. La-Doped TiO2 Nanoparticles for Photocatalysis: Synthesis, Activity in Terms of Degradation of Methylene Blue Dye and Regeneration of Used Nanoparticles. Arab. J. Sci. Eng. 2023, 48, 16431–16443. [Google Scholar] [CrossRef]
  8. Gong, Z.; Li, X.; Zhang, Z.; Liu, Y.; Song, H.; Wang, Y. Anodic Oxidation of TC4 Substrate to Synthesize Ce-Doped TiO2 Nanotube Arrays with Enhanced Photocatalytic Performance. J. Electron. Mater. 2021, 50, 3276–3282. [Google Scholar] [CrossRef]
  9. Kim, S.; An, E.; Oh, I.; Hwang, J.B.; Seo, S.; Jung, Y.; Park, J.-C.; Choi, H.; Choi, C.H.; Lee, S. CeO2 Nanoarray Decorated Ce-Doped ZnO Nanowire Photoanode for Efficient Hydrogen Production with Glycerol as a Sacrificial Agent. Catal. Sci. Technol. 2022, 12, 5517–5523. [Google Scholar] [CrossRef]
  10. Liu, Y.; Gu, T.; Bu, C.; Liu, D.; Piao, G. Investigation on the Activity of Ni Doped Ce0.8Zr0.2O2 for Solar Thermochemical Water Splitting Combined with Partial Oxidation of Methane. Int. J. Hydrogen Energy 2024, 62, 1077–1088. [Google Scholar] [CrossRef]
  11. Yang, Z.; Cui, Y.; Ge, P.; Chen, M.; Xu, L. CO2 Methanation over Rare Earth Doped Ni-Based Mesoporous Ce0.8Zr0.2O2 with Enhanced Low-Temperature Activity. Catalysts 2021, 11, 463. [Google Scholar] [CrossRef]
  12. Xu, L.; Wang, Y.; Yan, Y.; Hao, Z.; Chen, X.; Li, F. Optimisation of the Electronic Structure by Rare Earth Doping to Enhance the Bifunctional Catalytic Activity of Perovskites. Appl. Energy 2023, 339, 120931. [Google Scholar] [CrossRef]
  13. Dewoolkar, K.D.; Vaidya, P.D. Tailored Ce- and Zr-Doped Ni/Hydrotalcite Materials for Superior Sorption-Enhanced Steam Methane Reforming. Int. J. Hydrogen Energy 2017, 42, 21762–21774. [Google Scholar] [CrossRef]
  14. Cheng, Y.; Zhu, L.; Gong, Y. Ce Doped Ni(OH)2/Ni-MOF Nanosheets as an Efficient Oxygen Evolution and Urea Oxidation Reactions Electrocatalyst. Int. J. Hydrogen Energy 2024, 58, 416–425. [Google Scholar] [CrossRef]
  15. Duan, E.; Wang, Y.; Wang, S.; Bai, J.; Li, D.; Zhang, L.; Deng, J.; Tang, X. Revealing La Doping Activation or Inhibition of Crystal Facet Effects in Co3O4 for Catalytic Combustion and Water Resistance Improvement. Chem. Eng. J. 2024, 496, 153839. [Google Scholar] [CrossRef]
  16. Bae, J.; Shin, D.; Jeong, H.; Kim, B.-S.; Han, J.W.; Lee, H. Highly Water-Resistant La-Doped Co3O4 Catalyst for CO Oxidation. ACS Catal. 2019, 9, 10093–10100. [Google Scholar] [CrossRef]
  17. Wang, Y.; Li, S.; Song, J.; Qu, H.; Yu, S. High-Pressure Hydrothermal Dope Ce into MoVTeNbOx for One-Step Oxidation of Propylene to Acrylic Acid. Catal. Commun. 2024, 187, 106849. [Google Scholar] [CrossRef]
  18. Li, Q.; Yuan, G.; Pan, T.; Wang, Y.; Xu, Y.; Pang, H. Design of Fe-Doped Ni-Based Bimetallic Oxide Hierarchical Assemblies Boost Urea Oxidation Reaction. Int. J. Hydrogen Energy 2024, 93, 338–345. [Google Scholar] [CrossRef]
  19. Xie, K.; Jia, Q.; Wang, Y.; Zhang, W.; Xu, J. The Electronic Structure and Optical Properties of Anatase TiO2 with Rare Earth Metal Dopants from First-Principles Calculations. Materials 2018, 11, 179. [Google Scholar] [CrossRef]
  20. Wakhare, S.Y.; Deshpande, M.D. Rare Earth Metal Element Doped G-GaN Monolayer: Study of Structural, Electronic, Magnetic, and Optical Properties by First-Principle Calculations. Phys. B Condens. Matter 2022, 647, 414367. [Google Scholar] [CrossRef]
  21. Ducut, M.R.D.; Rojas, K.I.M.; Bautista, R.V.; Arboleda, N.B. Structural, Electronic, and Optical Properties of Copper Doped Monolayer Molybdenum Disulfide: A Density Functional Theory Study. Mater. Sci. Semicond. Process. 2025, 185, 108971. [Google Scholar] [CrossRef]
  22. Zhong, J.; Xu, Z.; Lu, J.; Li, Y.Y. Precise Electronic Structures of Amorphous Solids: Unraveling the Color Origin and Photocatalysis of Black Titania. J. Phys. Chem. C 2023, 127, 7268–7274. [Google Scholar] [CrossRef]
  23. Naik, K.M.; Hamada, T.; Higuchi, E.; Inoue, H. Defect-Rich Black Titanium Dioxide Nanosheet-Supported Palladium Nanoparticle Electrocatalyst for Oxygen Reduction and Glycerol Oxidation Reactions in Alkaline Medium. ACS Appl. Energy Mater. 2021, 4, 12391–12402. [Google Scholar] [CrossRef]
  24. Zheng, B.; Fan, J.; Chen, B.; Qin, X.; Wang, J.; Wang, F.; Deng, R.; Liu, X. Rare-Earth Doping in Nanostructured Inorganic Materials. Chem. Rev. 2022, 122, 5519–5603. [Google Scholar] [CrossRef] [PubMed]
  25. Zhao, Q.; Tian, X.; Ren, L.; Su, Y.; Su, Q. Understanding of Lanthanide-Doped Core–Shell Structure at the Nanoscale Level. Nanomaterials 2024, 14, 1063. [Google Scholar] [CrossRef]
  26. Bian, T.; Zhou, T.; Zhang, Y. Preparation and Applications of Rare-Earth-Doped Ferroelectric Oxides. Energies 2022, 15, 8442. [Google Scholar] [CrossRef]
  27. Dinamarca, R.; Garcia, X.; Jimenez, R.; Fierro, J.L.G.; Pecchi, G. Effect of A-Site Deficiency in LaMn0.9Co0.1O3 Perovskites on Their Catalytic Performance for Soot Combustion. Mater. Res. Bull. 2016, 81, 134–141. [Google Scholar] [CrossRef]
  28. Li, G.; Li, X.; Hao, X.; Li, Q.; Zhang, M.; Jia, H. Ti3+/Ti4+ and Co2+/Co3+ Redox Couples in Ce-Doped Co-Ce/TiO2 for Enhancing Photothermocatalytic Toluene Oxidation. J. Environ. Sci. 2025, 149, 164–176. [Google Scholar] [CrossRef]
  29. Nain, P.; Pawar, M.; Rani, S.; Sharma, B.; Kumar, S.; Majeed Khan, M.A. (Ce, Nd) Co-Doped TiO2 NPs via Hydrothermal Route:Structural, Optical, Photocatalytic and Thermal Behavior. Mater. Sci. Eng. B 2024, 309, 117648. [Google Scholar] [CrossRef]
  30. Li, Z.; Wang, E.; Zhang, Y.; Luo, R.; Gai, Y.; Ouyang, H.; Deng, Y.; Zhou, X.; Li, Z.; Feng, H. Antibacterial Ability of Black Titania in Dark: Via Oxygen Vacancies Mediated Electron Transfer. Nano Today 2023, 50, 101826. [Google Scholar] [CrossRef]
  31. Gulina, L.B.; Tolstoy, V.P.; Kasatkin, I.A.; Kolesnikov, I.E.; Danilov, D.V. Formation of Oriented LaF3 and LaF3: Eu3+ Nanocrystals at the Gas−Solution Interface. J. Fluor. Chem. 2017, 200, 18–23. [Google Scholar] [CrossRef]
  32. Gulina, L.B.; Schäfer, M.; Privalov, A.F.; Tolstoy, V.P.; Murin, I.V. Synthesis of LaF3 Nanosheets with High Fluorine Mobility Investigated by NMR Relaxometry and Diffusometry. J. Chem. Phys. 2015, 143, 234702. [Google Scholar] [CrossRef] [PubMed]
  33. Nagayama, S.; Kajihara, K.; Kanamura, K. Synthesis of Nanocrystalline LaF3 Doped Silica Glasses by Hydrofluoric Acid Catalyzed Sol–Gel Process. Mater. Sci. Eng. B 2012, 177, 510–514. [Google Scholar] [CrossRef]
  34. Stewart, L.; Lu, W.; Wei, Z.-W.; Ila, D.; Padilla, C.; Zhou, H.-C. A Zirconium Metal–Organic Framework with an Exceptionally High Volumetric Surface Area. Dalton Trans. 2017, 46, 14270–14276. [Google Scholar] [CrossRef]
  35. Hu, M.; Cao, Y.; Li, Z.; Yang, S.; Xing, Z. Ti3+ Self-Doped Mesoporous Black TiO2/SiO2 Nanocomposite as Remarkable Visible Light Photocatalyst. Appl. Surf. Sci. 2017, 426, 734–744. [Google Scholar] [CrossRef]
  36. Hong, Z.; Kang, M.; Chen, X.; Zhou, K.; Huang, Z.; Wei, M. Synthesis of Mesoporous Co2+-Doped TiO2 Nanodisks Derived from Metal Organic Frameworks with Improved Sodium Storage Performance. ACS Appl. Mater. Interfaces 2017, 9, 32071–32079. [Google Scholar] [CrossRef]
  37. Zhang, X.; Hu, W.; Zhang, K.; Wang, J.; Sun, B.; Li, H.; Qiao, P.; Wang, L.; Zhou, W. Ti3+ Self-Doped Black TiO2 Nanotubes with Mesoporous Nanosheet Architecture as Efficient Solar-Driven Hydrogen Evolution Photocatalysts. ACS Sustain. Chem. Eng. 2017, 5, 6894–6901. [Google Scholar] [CrossRef]
  38. Shi, X.; Guo, J.; Shen, T.; Fan, A.; Liu, Y.; Yuan, S. Improvement of NH3-SCR Activity and Resistance to SO2 and H2O by Ce Modified La-Mn Perovskite Catalyst. J. Taiwan Inst. Chem. Eng. 2021, 126, 102–111. [Google Scholar] [CrossRef]
  39. Liang, D.; Gao, J.; Sun, H.; Chen, P.; Hou, Z.; Zheng, X. Selective oxidation of glycerol with oxygen in a base-free aqueous solution over MWNTs supported Pt catalysts. Appl. Catal. B Environ. 2011, 106, 423–432. [Google Scholar] [CrossRef]
  40. Gao, J.; Liang, D.; Chen, P.; Hou, Z.; Zheng, X. Oxidation of glycerol with oxygen in a base-free aqueous solution over Pt/AC and Pt/MWNTs catalysts. Catal. Lett. 2009, 130, 185–191. [Google Scholar] [CrossRef]
  41. Ke, Y.; Xu, H.; Qin, H. Low-temperature catalytic oxidation of glycerol into glyceric acid over Zr@MCM-41-supported Pt catalyst. Chem. Lett. 2024, 53, upad021. [Google Scholar] [CrossRef]
  42. Chen, X.; Shen, L.; Yin, H. Selective conversion of glycerin to glyceric acid under mild and base-free conditions using layered double hydroxides-supported Pt nanoparticle catalysts. J. Chem. Technol. Biotechnol. 2023, 98, 2915–2924. [Google Scholar] [CrossRef]
  43. Liang, D.; Gao, J.; Wang, J.; Chen, P.; Wei, Y.; Hou, Z. Bimetallic Pt-Cu catalysts for glycerol oxidation with oxygen in a base-free aqueous solution. Catal. Commun. 2011, 12, 1059–1062. [Google Scholar] [CrossRef]
  44. Wu, G.; Liu, Y.; He, Y.; Feng, J.; Li, D. Reaction pathway investigation using in situ Fourier transform infrared technique over Pt/CuO and Pt/TiO2 for selective glycerol oxidation. Appl. Catal. B Environ. 2021, 291, 120061. [Google Scholar] [CrossRef]
  45. Feng, S.; Yi, J.; Miura, H.; Nakatani, N.; Hada, M.; Shishido, T.; Yan, H. Experimental and theoretical investigation of the role of bismuth in promoting the selective oxidation of glycerol over supported Pt-Bi catalyst under mild conditions. ACS Catal. 2020, 10, 6071–6083. [Google Scholar] [CrossRef]
  46. Zhang, X.; Zhou, D.; Wang, X.; Zhou, J.; Li, J.; Zhang, M.; Shen, Y.; Chu, H.; Qu, Y.; Yan, H. Overcoming the deactivation of Pt/CNT by introducing CeO2 for selective base-free glycerol-to-glyceric acid oxidation. ACS Catal. 2020, 10, 3832–3837. [Google Scholar] [CrossRef]
  47. Yan, H.; Qin, H.; Feng, X.; Jin, X.; Liang, W.; Sheng, N.; Zhu, C.; Wang, H.; Yin, B.; Liu, Y.; et al. Synergistic Pt/MgO/SBA-15 nanocatalysts for glycerol oxidation in base-free medium: Catalyst design and mechanistic study. J. Catal. 2019, 370, 434–446. [Google Scholar] [CrossRef]
  48. Panda, A.B.; Mahapatra, S.K.; Barhai, P.K.; Das, A.K.; Banerjee, I. Understanding of Gas Phase Deposition of Reactive Magnetron Sputtered TiO2 Thin Films and Its Correlation with Bactericidal Efficiency. Appl. Surf. Sci. 2012, 258, 9824–9831. [Google Scholar] [CrossRef]
  49. Abdullah, S.A.; Sahdan, M.Z.; Nafarizal, N.; Saim, H.; Embong, Z.; Cik Rohaida, C.H.; Adriyanto, F. Influence of Substrate Annealing on Inducing Ti3+ and Oxygen Vacancy in TiO2 Thin Films Deposited via RF Magnetron Sputtering. Appl. Surf. Sci. 2018, 462, 575–582. [Google Scholar] [CrossRef]
  50. Tereshchuk, P.; Chaves, A.S.; Da Silva, J.L. Glycerol adsorption on platinum surfaces: A density functional theory investigation with van der Waals corrections. J. Phys. Chem. C 2014, 118, 15251–15259. [Google Scholar] [CrossRef]
Crystals 15 00301 g001
Figure 1. XRD patterns of (a,b) Ce-B-TiO2 and (c,d) La-B-TiO2 with different doping ratios.
Figure 1. XRD patterns of (a,b) Ce-B-TiO2 and (c,d) La-B-TiO2 with different doping ratios.
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Figure 2. SEM image of Pt/4%La-B-TiO2 (a), EDS element distribution maps of Titanium (b), Oxygen (c), Lanthanum (d), and Platinum (e).
Figure 2. SEM image of Pt/4%La-B-TiO2 (a), EDS element distribution maps of Titanium (b), Oxygen (c), Lanthanum (d), and Platinum (e).
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Figure 3. SEM image of Pt/30%Ce-B-TiO2 (a), EDS element distribution maps of Titanium (b), Oxygen (c), Lanthanum (d), and Platinum (e).
Figure 3. SEM image of Pt/30%Ce-B-TiO2 (a), EDS element distribution maps of Titanium (b), Oxygen (c), Lanthanum (d), and Platinum (e).
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Figure 4. The conversion (a) and the selectivity (b) of Pt/Ce-B-TiO2 with different Ce doping ratios, The yield of Pt/Ce-B-TiO2 and Pt/La-B-TiO2 with different Ce or La doping ratios (c). The conversion of Pt/La-B-TiO2 with different La doping ratios (d).
Figure 4. The conversion (a) and the selectivity (b) of Pt/Ce-B-TiO2 with different Ce doping ratios, The yield of Pt/Ce-B-TiO2 and Pt/La-B-TiO2 with different Ce or La doping ratios (c). The conversion of Pt/La-B-TiO2 with different La doping ratios (d).
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Figure 5. The XPS spectra of Pt 4f and Ti 2p in Pt/30%Ce-B-TiO2 (a,d), Pt/50%Ce-B-TiO2 (b,e), and Pt/4%La-B-TiO2 (c,f).
Figure 5. The XPS spectra of Pt 4f and Ti 2p in Pt/30%Ce-B-TiO2 (a,d), Pt/50%Ce-B-TiO2 (b,e), and Pt/4%La-B-TiO2 (c,f).
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Figure 6. The XPS spectra of O 1s in Pt/30%Ce-B-TiO2 (a), Pt/50%Ce-B-TiO2 (b), and Pt/4%La-B-TiO2 (c).
Figure 6. The XPS spectra of O 1s in Pt/30%Ce-B-TiO2 (a), Pt/50%Ce-B-TiO2 (b), and Pt/4%La-B-TiO2 (c).
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Wang, Z.; Zhang, X.; Hai, B.; Zhang, H.; Ding, L. Effects of the Doping of La and Ce in the Pt/B-TiO2 Catalyst in Selective Oxidation Reaction of Glycerol. Crystals 2025, 15, 301. https://doi.org/10.3390/cryst15040301

AMA Style

Wang Z, Zhang X, Hai B, Zhang H, Ding L. Effects of the Doping of La and Ce in the Pt/B-TiO2 Catalyst in Selective Oxidation Reaction of Glycerol. Crystals. 2025; 15(4):301. https://doi.org/10.3390/cryst15040301

Chicago/Turabian Style

Wang, Zhihui, Xueqiong Zhang, Bo Hai, Hao Zhang, and Lijun Ding. 2025. "Effects of the Doping of La and Ce in the Pt/B-TiO2 Catalyst in Selective Oxidation Reaction of Glycerol" Crystals 15, no. 4: 301. https://doi.org/10.3390/cryst15040301

APA Style

Wang, Z., Zhang, X., Hai, B., Zhang, H., & Ding, L. (2025). Effects of the Doping of La and Ce in the Pt/B-TiO2 Catalyst in Selective Oxidation Reaction of Glycerol. Crystals, 15(4), 301. https://doi.org/10.3390/cryst15040301

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