A lanthanum cobalt nanomaterial with cobalt vacancies and a preparation method and application thereof
By introducing cobalt vacancies into the perovskite oxide LaCoO3, the problems of low charge separation efficiency and limited active sites were solved, achieving more efficient photocatalytic CO2 reduction, simplifying the preparation process and reducing costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CENT SOUTH UNIV
- Filing Date
- 2026-02-04
- Publication Date
- 2026-06-05
Smart Images
Figure CN122141682A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of photocatalytic materials technology, and more specifically, to a lanthanum cobalt oxide nanomaterial with cobalt vacancies, its preparation method, and its application. Background Technology
[0002] Currently, rapid global industrialization, while driving social progress, has also exacerbated the energy crisis and environmental pollution. The overexploitation of fossil fuels has led to excessively high atmospheric CO2 levels and ecological degradation. Therefore, exploring green and low-carbon energy conversion technologies is crucial for achieving sustainable development. Photocatalytic CO2 reduction technology, by simulating photosynthesis in nature, utilizes inexhaustible solar energy to drive electron transfer, converting CO2, a greenhouse gas, into hydrocarbon fuels or other high-value-added chemicals. This technology combines environmental remediation and energy regeneration, providing a promising solution for building a clean and low-carbon energy system.
[0003] In photocatalytic materials, perovskite oxides (ABO3) exhibit great application potential in environmental remediation and energy conversion due to their flexible crystal structure, excellent thermal stability, and tunable electronic properties. In the ideal LaCoO3 crystal structure, lanthanum ions at the A-site and cobalt ions at the B-site typically form saturated coordination with oxygen ions. While this lattice structure is stable, it is often accompanied by low charge separation efficiency and limited surface active sites, thus limiting its catalytic efficiency in practical photocatalytic reactions. Therefore, modification treatment is necessary.
[0004] Existing modification strategies mostly focus on A-site doping or creating oxygen vacancies through strong reduction treatment, but these methods often make it difficult to precisely control the type and distribution of defects and are very easy to damage the crystal structure of the material. Summary of the Invention
[0005] Based on the aforementioned technical problems in the prior art, the present invention provides a lanthanum cobalt oxide nanomaterial with cobalt vacancies. By introducing cobalt vacancies, not only can the rearrangement of local charge density be induced, but the construction of surface active sites can also be promoted through a charge compensation mechanism, thereby improving the performance of the lanthanum cobalt oxide nanomaterial.
[0006] To achieve the above objectives, the technical solution of the present invention is as follows:
[0007] A lanthanum cobalt oxide nanomaterial with cobalt vacancies, wherein the chemical formula of the lanthanum cobalt oxide is LaCo. 1-x O3; where 0.8≤1-x≤0.95.
[0008] In some implementations, 0.85 ≤ 1 - x ≤ 0.95.
[0009] This invention also provides a method for preparing the above-mentioned lanthanum cobalt oxide nanomaterials, the method comprising the following steps:
[0010] S1. Dissolve lanthanum source and cobalt source in water to obtain precursor solution; in the precursor solution, the molar ratio of lanthanum to cobalt is 1:(0.8-0.95).
[0011] S2. Dissolve the complexing agent in water to obtain a complexing agent solution;
[0012] S3. Under stirring, the complexing agent solution is added to the precursor solution, and a hydrothermal reaction is carried out until a gel is formed. Then, the gel is dried to obtain a dry gel.
[0013] S4. After grinding the dry gel, heat it to 550-700℃ and calcine it to obtain lanthanum cobalt oxide nanomaterials with cobalt vacancies.
[0014] In some embodiments, in step S3, the molar ratio of citric acid to total metal ions is 1:(0.9-1.3).
[0015] In some embodiments, in step S1, the molar ratio of lanthanum to cobalt is 1:(0.85-0.95).
[0016] In some embodiments, the temperature of the hydrothermal reaction in step S3 is 75-85°C.
[0017] In some embodiments, the drying temperature in step S3 is 90-130°C.
[0018] In some embodiments, the lanthanum source is a soluble salt of lanthanum; the cobalt source is a soluble salt of cobalt; and the complexing agent includes citric acid.
[0019] In some implementations, the heating rate in step S3 is 1-5°C / min.
[0020] In some embodiments, the calcination time in step S3 is 4-8 hours.
[0021] In some implementations, the drying time in step S2 is 8-24 hours.
[0022] This invention also provides the application of the above-mentioned lanthanum cobalt oxide nanomaterials with cobalt vacancies as catalysts in photocatalytic CO2 reduction.
[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0024] The lanthanum cobalt oxide nanomaterial provided by this invention introduces a specific ratio of cobalt vacancies and effectively modulates the electronic structure of the material through defect energy levels, providing abundant active sites. This enables the material to exhibit stronger photogenerated charge separation ability and higher catalytic performance in photocatalytic CO2 reduction, thereby improving the catalytic efficiency of CO2 reduction.
[0025] The preparation method provided by this invention abandons the complex post-processing etching process and directly controls the precursor stoichiometry in the sol-gel process. It successfully introduces a controllable proportion of cobalt vacancies while maintaining the lanthanum cobalt oxide crystal structure. This not only provides more active sites for lanthanum cobalt oxide nanomaterials and improves the catalytic performance of the materials, but also simplifies the process, reduces production costs, and is suitable for industrial applications. Attached Figure Description
[0026] Figure 1 The X-ray diffraction (XRD) patterns of the LaCoO3 nanomaterial photocatalysts containing cobalt vacancies prepared in Comparative Example 1 and Examples 1-3 of this invention are shown.
[0027] Figure 2 LaCo prepared in Example 2 of this invention 0.9 Scanning electron microscope (SEM) image of O3 nanomaterial photocatalyst.
[0028] Figure 3 LaCo prepared in Example 2 of this invention 0.9 Transmission electron microscopy (TEM) image of O3 nanomaterial photocatalyst.
[0029] Figure 4 The LaCoO3 prepared in Comparative Example 1 and the LaCoO3 prepared in Example 2 of this invention 0.9 Photocurrent response (It) spectrum of O3 nanostructured photocatalyst.
[0030] Figure 5 The LaCoO3 prepared in Comparative Example 1 and the LaCoO3 prepared in Example 2 of this invention 0.9 Electrochemical impedance spectroscopy (EIS) of O3 nanostructured photocatalysts.
[0031] Figure 6 The LaCoO3 prepared in Comparative Example 1 and the LaCoO3 prepared in Example 2 of this invention 0.9 Fluorescence (PL) spectrum of O3 nanostructure photocatalyst.
[0032] Figure 7 The graphs show the photocatalytic CO2 reduction performance of the photocatalysts prepared in Comparative Example 1 and Examples 1-3 of this invention. Detailed Implementation
[0033] Numerous specific details are set forth in the following description to provide a full understanding of the invention. However, the invention can be practiced in many other ways different from those described herein, and similar modifications can be made by those skilled in the art without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.
[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
[0035] Comparative Example 1: Preparation of Standard Stoichiometric LaCoO3
[0036] A method for preparing LaCoO3 nanomaterials includes the following steps:
[0037] According to the stoichiometric ratio of La:Co = 1:1, 5 mmol of La(NO3)3·6H2O and 5 mmol of Co(NO3)2·6H2O were weighed and dissolved in 30 mL of deionized water, and this solution was denoted as solution A. 10 mmol of citric acid was weighed and dissolved in 10 mL of deionized water, and this solution was denoted as solution B. Solution B was slowly added dropwise to solution A under magnetic stirring. The mixture was continuously heated and stirred in an 80 °C water bath. As the water evaporated, the viscosity of the solution gradually increased, and it eventually turned into a purple-red gel.
[0038] The obtained gel was transferred to a forced-air drying oven and dried at 120 °C for 12 hours to obtain a loose and porous purplish-red dry gel. After grinding, the powder was placed in a muffle furnace and heated to 600 °C at a rate of 2 °C / min in air atmosphere and held at that temperature for 6 hours. After natural cooling, it was ground a second time to obtain the LaCoO3 sample.
[0039] Example 1: Possessing trace amounts of cobalt vacancies (LaCo) 0.95 Preparation of O3
[0040] To investigate the effect of a low cobalt vacancy ratio on performance, the amount of cobalt source was adjusted to 4.75 mmol (La:Co = 1:0.95), while the remaining steps remained the same as in Comparative Example 1. During the preparation process, it was observed that the gelation time changed slightly with fine adjustments to the cobalt content.
[0041] Example 2: With a moderate cobalt vacancy ratio (LaCo) 0.9 Preparation of O3
[0042] This embodiment aims to prepare cobalt vacancy-type lanthanum cobaltate with a La / Co molar ratio of 1:0.9. The specific operation is as follows: 5 mmol of La(NO3)3·6H2O and 4.5 mmol of Co(NO3)2·6H2O were accurately weighed and dissolved in 30 mL of deionized water, and this solution is denoted as solution A; citric acid (with a molar ratio of approximately 1:1 to the total metal ions) was weighed and dissolved in 10 mL of deionized water, and this solution is denoted as solution B; under magnetic stirring, solution B was added dropwise to solution A at a rate of 1 drop per second. The mixture was continuously heated in an 80 °C water bath to remove excess water, resulting in a purple-red wet gel.
[0043] The obtained wet gel was dried at 120 °C for 12 hours to obtain a loose and porous purplish-red dry gel. After grinding, the powder was placed in a muffle furnace and heated to 600 °C at a rate of 2 °C / min in air atmosphere and held at that temperature for 6 hours. After natural cooling, it was ground a second time to obtain LaCo. 0.9 O3.
[0044] Example 3: With a high proportion of cobalt vacancies (LaCo) 0.85 Preparation of O3
[0045] The amount of cobalt nitrate was further reduced to 4.25 mmol (La:Co = 1:0.85), while the remaining steps remained the same as in Comparative Example 1, to prepare a sample with a high proportion of cobalt vacancies.
[0046] The samples obtained in Comparative Example 1 and Examples 1-3 were detected by inductively coupled plasma optical emission spectrometry (ICP-OES), and the results are shown in Table 1.
[0047] Table 1. ICP-OES detection results of samples from Examples 1-3 and Comparative Example 1
[0048]
[0049] As shown in Table 1, the actual La:Co molar ratios of the materials prepared in Comparative Example 1 and Examples 1-3 are given by ICP-OES testing, indicating that the actual molar ratios are basically consistent with the theoretical molar ratios, and the controllable synthesis of cobalt vacancies in LaCoO3 has been achieved.
[0050] The samples obtained in Comparative Example 1 and Examples 1-3 were subjected to XRD analysis, and the results are as follows: Figure 1 As shown.
[0051] like Figure 1The sample prepared in Comparative Example 1 showed good crystallinity, and no other crystalline phases appeared in the X-ray diffraction pattern, indicating that it was pure LaCoO3. In Examples 1-3, after introducing cobalt vacancies, no obvious impurity phases were detected in the X-ray diffraction patterns, indicating that the main crystalline phase remained unchanged. The diffraction peaks broadened to varying degrees, especially the originally split (110) and (104) characteristic diffraction peaks, which gradually broadened and showed a tendency to overlap. The changes in the diffraction peaks confirmed the lattice changes induced by the introduction of cobalt vacancies, which may be related to the changes in lattice parameters and the adjustment of internal stress state caused by cobalt vacancies and associated oxygen vacancies, thereby improving the stability of the crystal structure to a certain extent.
[0052] Figure 2 This is a scanning electron microscope (SEM) image of LaCoO3 obtained in Example 2. Figure 2 LaCo 0.9 O3 is composed of ultrathin nanosheets made up of nanospheres.
[0053] Figure 3 The LaCo prepared in Example 2 of this paper 0.9 Transmission electron microscopy (TEM) images of O3 reveal a sheet-like nanosphere structure.
[0054] Figure 4 The instantaneous photocurrent (It) spectra of the samples prepared in Comparative Example 1 and Example 2 are shown. Figure 4 As can be seen, the instantaneous photocurrent intensity of lanthanum cobalt oxide with cobalt vacancies is significantly increased. The increase in photocurrent means an increase in the number of photogenerated electrons, which is more conducive to the photocatalytic reaction.
[0055] Figure 5 The images show the electrochemical impedance spectroscopy (EIS) spectra of the samples prepared in Comparative Example 1 and Example 2. Figure 5 As shown, compared to lanthanum cobaltate which does not contain cobalt vacancies, LaCo... 0.9 The arc radius of the electrochemical impedance of O3 nanomaterials is significantly reduced, which means that the smaller the impedance, the higher the charge transfer efficiency, which is beneficial to improving the photocatalytic reaction activity.
[0056] Figure 6 The photoluminescence (PL) spectra of the samples prepared in Comparative Example 1 and Example 2 are shown. Figure 6 LaCo with cobalt vacancies 0.9 The fluorescence intensity of the O3 sample decreased significantly, indicating that the recombination of photogenerated charge carriers was effectively suppressed, thereby improving photocatalytic activity. This is consistent with the results of photocurrent and impedance analysis.
[0057] The photocatalytic CO2 performance of the samples prepared in Comparative Example 1 and Examples 1-3 was tested, as follows:
[0058] Weigh 10 mg of each prepared sample, add 1-2 mL of deionized water, sonicate until homogeneous, pour into a 3 cm diameter glass dish and dry to form a thin film. Place the glass dish into the dried photoreactor and seal it. Alternately evacuate and purge with nitrogen until all air is expelled. Continuously purge with high-purity CO2 gas for 30 min, then inject 3 mL of deionized water. Use a 300 W xenon lamp as the light source, and maintain the temperature with circulating condensate water. React for four hours, and extract 1 mL of gas every hour to detect the product content in a gas chromatograph.
[0059] Test results are as follows Figure 7 As shown.
[0060] like Figure 7 Under visible light irradiation, the CO / CH4 yield of LaCoO3 prepared in Comparative Example 1 was significantly lower than that in Examples 1, 2, and 3, which constructed cobalt vacancies. This indicates that the introduction of cobalt vacancies can increase the number of reactive sites, improve the separation efficiency of photogenerated carriers, and thus enhance the photocatalytic reduction performance of CO2. Furthermore, Example 2 exhibited the best photocatalytic performance, with a CO yield of 17.02 μmol·g. -1 ·h -1 This is 3.06 times that of Comparative Example 1; CH4 yield was 19.60 μmol·g. -1 ·h -1 This is 1.81 times that of Comparative Example 1. Therefore, it is evident that the proportion of cobalt vacancies in lanthanum cobaltate significantly affects photocatalytic activity; an appropriate proportion of cobalt vacancies exhibits the highest catalytic activity, highlighting the importance of introducing cobalt vacancies into lanthanum cobaltate in this invention.
[0061] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0062] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.
Claims
1. A lanthanum cobalt oxide nanomaterial with cobalt vacancies, characterized in that, The chemical formula of the lanthanum cobaltate is LaCo. 1- x O3; where 0.8≤1-x≤0.
95.
2. The method for preparing lanthanum cobalt oxide nanomaterials with cobalt vacancies as described in claim 1, characterized in that, Includes the following steps: S1. Dissolve lanthanum source and cobalt source in water to obtain precursor solution; in the precursor solution, the molar ratio of lanthanum to cobalt is 1:(0.8-0.95). S2. Dissolve the complexing agent in water to obtain a complexing agent solution; S3. Under stirring, the complexing agent solution is added to the precursor solution, and a hydrothermal reaction is carried out until a gel is formed. Then, the gel is dried to obtain a dry gel. S4. After grinding the dry gel, heat it to 550-700℃ and calcine it to obtain lanthanum cobalt oxide nanomaterials with cobalt vacancies.
3. The method for preparing lanthanum cobalt oxide nanomaterials with cobalt vacancies according to claim 2, characterized in that, In step S3, the molar ratio of the complexing agent to the total metal ions is 1:(0.9-1.3).
4. The method for preparing lanthanum cobalt oxide nanomaterials with cobalt vacancies according to claim 2, characterized in that, In step S3, the temperature of the hydrothermal reaction is 75-85℃.
5. The method for preparing lanthanum cobalt oxide nanomaterials with cobalt vacancies according to claim 2, characterized in that, In step S3, the drying temperature is 90-130℃.
6. The method for preparing lanthanum cobalt oxide nanomaterials with cobalt vacancies according to claim 2, characterized in that, The lanthanum source is a soluble salt of lanthanum; the cobalt source is a soluble salt of cobalt; and the complexing agent includes citric acid.
7. The method for preparing lanthanum cobalt oxide nanomaterials with cobalt vacancies according to claim 2, characterized in that, In step S3, the heating rate is 1-5℃ / min; and / or the calcination time is 4-8h.
8. The method for preparing lanthanum cobalt oxide nanomaterials with cobalt vacancies according to claim 2, characterized in that, In step S2, the drying time is 8-24 hours.
9. The application of the lanthanum cobalt oxide nanomaterial with cobalt vacancies as described in claim 1 as a catalyst in photocatalytic CO2 reduction.