Cesium bismuth bromide / cobalt monatomic-nitrogen doped graphene, and preparation method and application thereof

Abstract

The application belongs to the technical field of new energy and photocatalysis, and particularly relates to cesium bismuth bromide / cobalt monatomic-nitrogen doped graphene as well as a preparation method and application thereof. The preparation method comprises the following steps: dissolving a carbon source and a nitrogen dopant in deionized water, adding a cobalt salt solution to obtain a mixed solution after ultrasonic mixing, annealing a solid obtained after the mixed solution is evaporated to dryness to obtain cobalt monatomic-nitrogen doped graphene; dissolving cesium bromide and bismuth bromide in dimethyl sulfoxide to obtain a precursor solution, adding the precursor solution into an isopropyl alcohol solution in which the cobalt monatomic-nitrogen doped graphene is dispersed, and crystallizing by an anti-solvent method to obtain the cesium bismuth bromide / cobalt monatomic-nitrogen doped graphene. The cesium bismuth bromide / cobalt monatomic-nitrogen doped graphene obtained by the application realizes efficient conversion of CO2 into CO under light irradiation, and has the advantages of simple preparation method, mild reaction condition, no pollution, high selectivity and the like.

Description

Technical Field

[0001] This invention belongs to the fields of new energy and photocatalysis technology, specifically relating to a cesium bismuth bromide / cobalt single-atom nitrogen-doped graphene, its preparation method, and its application. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Solar-driven CO2 photoreduction can reduce atmospheric CO2 concentration and produce high-value-added fuels and chemicals, providing an attractive pathway for CO2 recycling. In pursuit of ideal CO2 conversion efficiency, various semiconductor materials such as TiO2, CdS, g-C3N4, ZnO, and Cu2O have been explored. However, problems such as narrow light absorption range, severe charge recombination, and low light conversion efficiency have resulted in less than ideal photocatalytic activity. Therefore, developing novel photocatalysts or photocatalytic systems to achieve efficient CO2 conversion remains a key focus of future research.

[0004] Among semiconductor materials used for photocatalytic CO2 reduction, halide perovskites have attracted much attention due to their excellent properties such as wide light absorption range, long carrier diffusion length, and tunable energy levels. In particular, halide perovskites, represented by CsPbBr3, have shown excellent activity in photocatalytic CO2 reduction and have broad application prospects. However, lead, as one of the heavy metal pollutants, has severely limited the further development of lead-based halide perovskites due to its toxicity. In recent years, lead-free and non-toxic halide perovskites have received widespread attention in photocatalytic CO2 reduction. Although lead-free halide perovskites have achieved preliminary applications in CO2 photoreduction, they still suffer from slow charge separation and severe carrier recombination, and their photocatalytic activity still cannot meet the requirements for efficient CO2 photoreduction. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a cesium bismuth bromide / cobalt single-atom nitrogen-doped graphene, its preparation method, and its applications. This invention combines cobalt single-atom nitrogen-doped graphene (Co-NG) with high electrical conductivity with cesium bismuth bromide (Cs3Bi2Br9) possessing suitable valence and conduction bands and high reducing power. The resulting cesium bismuth bromide / cobalt single-atom nitrogen-doped graphene (Cs3Bi2Br9 / Co-NG) achieves efficient CO2 conversion to CO under light irradiation, offering advantages such as simple preparation method, mild reaction conditions, no pollution, and high selectivity.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0007] In a first aspect, a method for preparing cesium bismuth bromide / cobalt single-atom nitrogen-doped graphene includes the following steps:

[0008] S1. Dissolve the carbon source and nitrogen dopant in deionized water, add cobalt salt solution and mix ultrasonically to obtain a mixed solution. After evaporating the solvent from the mixed solution, anneal the obtained solid to obtain cobalt single-atom nitrogen-doped graphene.

[0009] S2. Cesium bromide and bismuth bromide are dissolved in dimethyl sulfoxide to obtain a precursor solution. The precursor solution is added to an isopropanol solution containing cobalt single-atom nitrogen-doped graphene. Cesium bismuth bromide / cobalt single-atom nitrogen-doped graphene is obtained by antisolvent crystallization.

[0010] Graphene, as a highly conductive electron acceptor and transporter, can enhance the performance of semiconductor photocatalysts by promoting the transfer of photogenerated electrons. Furthermore, by anchoring single atoms, graphene can significantly alter its electronic structure and properties, resulting in unique photoelectric effects, more active sites, and excellent catalytic activity and selectivity. Therefore, introducing single-atom-anchored graphene as an ideal electronic medium in halide perovskites can improve CO2 photoreduction performance by suppressing the recombination of photogenerated electrons and holes and promoting charge migration.

[0011] Preferably, in step S1, the carbon source includes glucose, and the nitrogen dopant includes dicyandiamide.

[0012] Preferably, in step S1, the molar ratio of cobalt salt, carbon source and nitrogen dopant is 1:(80-85):(3500-3600).

[0013] Preferably, in step S1, the annealing temperature is 750–850°C and the time is 2–4 hours.

[0014] Preferably, in step S1, the product is washed with ethanol and deionized water and dried after annealing.

[0015] Preferably, in step S2, the ratio of cesium bromide, bismuth bromide, and cobalt single-atom nitrogen-doped graphene is (2.9–3.1 mol):(2 mol):(50–450 g).

[0016] Preferably, in step S2, the cesium bismuth bromide / cobalt single-atom nitrogen-doped graphene obtained by crystallization is washed with ethanol and dried.

[0017] In a second aspect, a cesium bismuth bromide / cobalt single-atom nitrogen-doped graphene is characterized by being obtained by the preparation method described in the first aspect.

[0018] Thirdly, as described in the second aspect, the application of cesium bismuth bromide / cobalt single-atom nitrogen-doped graphene in photocatalytic reactions.

[0019] Preferably, the photocatalytic reaction is the photocatalytic reduction of carbon dioxide to carbon monoxide.

[0020] The beneficial effects achieved by one or more technical solutions of the present invention are as follows:

[0021] Co-NG, as a cocatalyst, possesses high electrical conductivity and abundant reactive sites. Loading it onto Cs3Bi2Br9 significantly improves carrier transport and separation efficiency. The Cs3Bi2Br9 / Co-NG photocatalyst exhibits highly efficient photocatalytic CO2 reduction activity, with a CO yield of 123.16 μmol g. -1 h -1 It exhibits near 100% selectivity and maintains excellent stability in long-term testing.

[0022] The preparation method of Cs3Bi2Br9 / Co-NG photocatalyst is simple, the reaction conditions are mild, the cost is low, it can be prepared on a large scale, and it is pollution-free. Attached Figure Description

[0023] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0024] Figure 1 The images show (a) SEM image, (b) TEM image, (c) STEM-HADDF image and (d) magnified image of Co-NG, the product of Example 1.

[0025] Figure 2 The image shows the synchrotron radiation spectrum of Co-NG in Example 1, where a is the X-ray near-edge absorption fine structure spectrum and b is the Fourier transform extended X-ray absorption spectrum.

[0026] Figure 3 (a) SEM image and (b) TEM image of the Cs3Bi2Br9 photocatalyst in Comparative Example 1;

[0027] Figure 4 The images shown are (a) TEM images and (b) SEM images of the Cs3Bi2Br9 / Co-NG photocatalyst in Example 1.

[0028] Figure 5 (a) XRD pattern, (b) UV-Vis absorption spectrum, (c) XPS Cs 3d spectrum, (d) XPS Bi 4f spectrum, (e) XPS Br 3d spectrum and (f) XPS Co2p spectrum for Cs3Bi2Br9 of Comparative Example 1, Co-NG of Example 1 and Cs3Bi2Br9 / Co-NG;

[0029] Figure 6 (a) Photocatalytic CO2 reduction activity graph of Cs3Bi2Br9 in Comparative Example 1 and Cs3Bi2Br9 / Co-NG in Examples 1-5 and (b) Stability test graph of Cs3Bi2Br9 / Co-NG in Example 1;

[0030] Figure 7 (a) transient PL spectrum and (b) fluorescence lifetime spectrum of Cs3Bi2Br9 in Comparative Example 1 and Cs3Bi2Br9 / Co-NG in Example 1;

[0031] Figure 8 The photoelectric test diagrams are for Cs3Bi2Br9 in Comparative Example 1 and Cs3Bi2Br9 / Co-NG in Example 1, where a is the photocurrent density test and b is the impedance test.

[0032] Figure 9 The image shows the in-situ infrared spectrum of Cs3Bi2Br9 / Co-NG under photocatalytic CO2 reaction conditions in Example 1. Detailed Implementation

[0033] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments and comparative examples.

[0034] Example 1

[0035] Dissolve 0.1 g glucose and 2 g dicyandiamide in deionized water and stir vigorously at 60 °C until completely dissolved. Add 1.6 mL of 4.2 mM CoCl2·6H2O aqueous solution to the above mixture, sonicate for 30 min, and then stir vigorously at 60 °C for at least 24 hours to evaporate the water. Grind the dried sample and incubate at 800 °C in argon atmosphere for 3 °C min. -1 Annealing was carried out at a rate of 2 h. The powder was washed three times with ethanol and deionized water to obtain black cobalt single-atom nitrogen-doped graphene (Co-NG) powder.

[0036] 0.128 g CsBr and 0.179 g BiBr3 were added to 20 mL of dimethyl sulfoxide and stirred vigorously until completely dissolved to obtain a precursor solution. 5 mg Co-NG was dispersed in 30 mL of isopropanol and ultrasonically dispersed until homogeneous. Then, 2 mL of the precursor solution was injected into the isopropanol, allowing Cs3Bi2Br9 to grow by antisolvent crystallization on Co-NG. The solution was centrifuged and the dark green precipitate was washed repeatedly with ethanol and dried to obtain cesium bismuth bromide / cobalt single-atom nitrogen-doped graphene (Cs3Bi2Br9 / Co-NG).

[0037] Comparative Example 1

[0038] 0.128 g CsBr and 0.179 g BiBr3 were added to 20 mL of dimethyl sulfoxide and stirred vigorously until completely dissolved to obtain a precursor solution. Then, 2 mL of the precursor solution was injected into 30 mL of isopropanol for antisolvent crystallization. The solution was centrifuged and the yellow precipitate was washed several times with ethanol and dried to obtain cesium bismuth bromide (Cs3Bi2Br9).

[0039] The SEM and TEM images of Co-NG are as follows: Figure 1 As shown in figures a and b, Co-NG exhibits a continuously cross-linked sheet structure without nanoparticle aggregation. STEM-HADDF images are shown below. Figure 1 As shown in c and d, the bright spots in the figures represent the distribution of cobalt atoms on the graphene surface.

[0040] The synchrotron radiation spectrum of Co-NG is as follows: Figure 2 As shown. Figure 2 The X-ray near-edge absorption fine structure spectrum of a in the image shows that the absorption edge of the Co K-edge is located at CoPc(Co) II Nearby, rather than Co foil (Co) 0 The presence of ) near the coordinate environment of a single Co atom indicates the coordination environment of the Co atom. Figure 2 The Fourier transform extended X-ray absorption spectrum in b indicates that the main peak of Co-NG is located at... Consistent with CoPc, this indicates that the cobalt atom is coordinated with four N atoms through the Co-N4 structure.

[0041] SEM image of Cs3Bi2Br9 is shown below. Figure 3 As shown in Figure a, the prepared Cs3Bi2Br9 has a two-dimensional planar hexagonal structure with dimensions ranging from 50 to 200 nm. TEM images of the Cs3Bi2Br9 photocatalyst are shown below. Figure 3 As shown in b, a lattice pattern with a spacing of 0.33 nm was observed, corresponding to the (003) plane of Cs3Bi2Br9.

[0042] TEM and SEM images of the Cs3Bi2Br9 / Co-NG photocatalyst are shown below. Figure 4 As shown in a and b, Cs3Bi2Br9 was observed to be in close contact with Co-NG.

[0043] XRD patterns of Cs3Bi2Br9, Co-NG, and Cs3Bi2Br9 / Co-NG are shown below. Figure 5As shown in Figure a, the XRD patterns of Cs3Bi2Br9 and Cs3Bi2Br9 / Co-NG match well with hexagonal Cs3Bi2Br9 (PDF#44-0714). Furthermore, no XRD peaks of Co-NG were detected in the XRD pattern of Cs3Bi2Br9 / Co-NG, likely due to the relatively low loading of Co-NG. The UV-Vis absorption spectra of Cs3Bi2Br9, Co-NG, and Cs3Bi2Br9 / Co-NG are shown below. Figure 5 As shown in b, the absorption edge of Cs3Bi2Br9 is located at 470 nm. After constructing the Cs3Bi2Br9 / Co-NG composite material, the light absorption edge shows a red shift, and the absorption tail is significantly increased, indicating that the loading of Co-NG promotes the light absorption of Cs3Bi2Br9 / Co-NG. The XPS plots of Cs3Bi2Br9, Co-NG, and Cs3Bi2Br9 / Co-NG are shown in Figure 1. Figure 5 As shown in Figure cf, the peak positions of Cs 3d, Bi 4f, and Br 3d in the Cs3Bi2Br9 / Co-NG composite all show significant positive shifts compared to Cs3Bi2Br9, at 0.18, 0.12, and 0.21 eV, respectively. However, compared to Co-NG, the peak of the Co 2p spectrum in the Cs3Bi2Br9 / Co-NG composite is shifted to the lower binding energy by 0.44 eV. These results indicate a strong electronic interaction between Cs3Bi2Br9 and Co-NG, with electrons from Cs3Bi2Br9 more readily transferring to Co-NG, which is beneficial for the subsequent photoreduction process at the Co-NG sites.

[0044] Example 2

[0045] Unlike Example 1, 1 mg of Co-NG was dispersed in 30 mL of isopropanol to obtain cesium bismuth bromide / cobalt single-atom nitrogen-doped graphene, denoted as Cs3Bi2Br9 / 1Co-NG.

[0046] Example 3

[0047] Unlike Example 1, 3 mg of Co-NG was dispersed in 30 mL of isopropanol to obtain cesium bismuth bromide / cobalt single-atom nitrogen-doped graphene, denoted as Cs3Bi2Br9 / 3Co-NG.

[0048] Example 4

[0049] Unlike Example 1, 7 mg of Co-NG was dispersed in 30 mL of isopropanol to obtain cesium bismuth bromide / cobalt single-atom nitrogen-doped graphene, denoted as Cs3Bi2Br9 / 7Co-NG.

[0050] Example 5

[0051] Unlike Example 1, 9 mg of Co-NG was dispersed in 30 mL of isopropanol to obtain cesium bismuth bromide / cobalt single-atom nitrogen-doped graphene, denoted as Cs3Bi2Br9 / 9Co-NG.

[0052] Example 6

[0053] The photocatalytic reaction was carried out in a 200 mL quartz reaction cell under top illumination. 10 mg of photocatalyst (cesium bismuth bromide / cobalt single-atom nitrogen-doped graphene from Examples 1-5 or Cs3Bi2Br9 from Comparative Example 1) was uniformly dispersed in the center of the reactor, and 50 μL of H2O was dropped onto the edge of the reactor. The reactor was sealed, and high-purity CO2 was bubbled for 20 min to fill the reactor with CO2 gas. A 300 W xenon lamp was used as the light source, and the light intensity was calibrated to 200 mW cm⁻¹ using a power meter. -2 The reaction suspension was maintained at 298 K using a cooling water stream. The separated gases were analyzed by gas chromatography.

[0054] Photocatalytic CO2 reduction activity and stability test results for Cs3Bi2Br9 and Cs3Bi2Br9 / Co-NG are shown below. Figure 6 As shown, the photocatalytic CO2 reduction activity of Cs3Bi2Br9 is generally low, with a CO yield of only 7.11 μmol g. -1 h -1 Subsequently, a series of Cs3Bi2Br9 / xCo-NG samples with different Co-NG loadings (Examples 1-5, where the cesium bismuth bromide / cobalt single-atom nitrogen-doped graphene of Example 1 is designated as Cs3Bi2Br9 / 5Co-NG) were tested, such as Figure 6 As shown in Figure 1, the photocatalytic CO2 reduction activity of Cs3Bi2Br9 was significantly improved after the introduction of Co-NG. By optimizing the loading of Co-NG, the CO yield of Cs3Bi2Br9 / 5Co-NG reached 123.16 μmol g. - 1 h -1 It is 17.3 times that of Cs3Bi2Br9. For example... Figure 6 As shown in b, the activity of Cs3Bi2Br9 / Co-NG in Example 1 did not decrease significantly after 4 hours of cycling and 5 cycles, indicating that it has stability.

[0055] The transient PL spectra of Cs3Bi2Br9 and Cs3Bi2Br9 / Co-NG are as follows: Figure 7As shown in Figure a, Cs3Bi2Br9 exhibits a strong emission peak at 463 nm due to the rapid recombination of photogenerated carriers. In contrast, significant PL quenching is observed in Cs3Bi2Br9 / Co-NG, which is attributed to the effective promotion of charge separation and suppression of carrier recombination by the introduction of Co-NG. The fluorescence lifetime spectra of Cs3Bi2Br9 and Cs3Bi2Br9 / Co-NG are shown in Figure a. Figure 7 As shown in b, the shortened PL lifetime of Cs3Bi2Br9 / Co-NG indicates that the charge was efficiently transferred from Cs3Bi2Br9 to Co-NG, which promoted charge separation and surface CO2 reduction.

[0056] The photoelectric test results of Cs3Bi2Br9 and Cs3Bi2Br9 / Co-NG from Example 1 are shown below. Figure 8 As shown, the photocurrent of Cs3Bi2Br9 / Co-NG is significantly enhanced compared to Cs3Bi2Br9, indicating that photoexcited carrier transfer in Cs3Bi2Br9 / Co-NG is greatly promoted. Furthermore, Cs3Bi2Br9 / Co-NG exhibits a smaller semicircle in the impedance diagram, suggesting a more convenient charge transfer process.

[0057] The in-situ infrared spectrum of Cs3Bi2Br9 / Co-NG under photocatalytic CO2 reaction conditions in Example 1 is shown below. Figure 9 As shown, a series of reaction intermediates were detected, including adsorbed H2O (1645 cm⁻¹). -1 m-CO3 2- (1402cm -1 and 1547cm -1 ) and β-CO3 2- (1508cm -1 and 1270cm -1 ). At 1691cm -1 and 1310cm -1 CO2 was observed at [location]. - The adsorption peaks show a gradual increase in adsorption strength, indicating that CO2 molecules are continuously activated and converted into CO2. - Additionally, the adsorption peak of *COOH, considered a key intermediate in the selective reduction of CO2 to CO, is located at 1620 cm⁻¹. -1 and 1460cm -1 These results indicate that CO2 molecules adsorbed on the Cs3Bi2Br9 / Co-NG surface are photoactivated into CO2. - It is selectively converted to CO by forming the key intermediate *COOH.

[0058] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing cesium bismuth bromide (Cs3Bi2Br9) / cobalt single-atom nitrogen-doped graphene, characterized in that, Includes the following steps: S1. Dissolve the carbon source and nitrogen dopant in deionized water, add cobalt salt solution and mix ultrasonically to obtain a mixed solution. After evaporating the solvent from the mixed solution, anneal the obtained solid to obtain cobalt single-atom nitrogen-doped graphene. The molar ratio of cobalt salt, carbon source and nitrogen dopant is 1:(80~85):(3500~3600). S2. Cesium bromide and bismuth bromide were dissolved in dimethyl sulfoxide to obtain a precursor solution. The precursor solution was added to an isopropanol solution containing cobalt single-atom nitrogen-doped graphene. Cesium bismuth bromide Cs3Bi2Br9 / cobalt single-atom nitrogen-doped graphene was obtained by antisolvent crystallization. The ratio of cesium bromide, bismuth bromide and cobalt single-atom nitrogen-doped graphene was (2.9~3.1 mol):(2mol):(50~450 g).

2. The preparation method according to claim 1, characterized in that, In step S1, the carbon source includes glucose, and the nitrogen dopant includes dicyandiamide.

3. The preparation method according to claim 1, characterized in that, In step S1, the annealing temperature is 750~850 ℃ and the time is 2~4 h.

4. The preparation method according to claim 1, characterized in that, In step S1, after annealing, the product is washed with ethanol and deionized water and then dried.

5. The preparation method according to claim 1, characterized in that, In step S2, the cesium bismuth bromide (Cs3Bi2Br9) / cobalt single-atom nitrogen-doped graphene obtained by crystallization is washed with ethanol and dried.

6. A cesium bismuth bromine (Cs3Bi2Br9) / cobalt single-atom nitrogen-doped graphene, characterized in that, Obtained by the preparation method described in any one of claims 1 to 5.

7. The application of cesium bismuth bromine (Cs3Bi2Br9) / cobalt single-atom nitrogen-doped graphene as described in claim 6 in photocatalytic reactions.

8. The application as described in claim 7, characterized in that, The photocatalytic reaction is the photocatalytic reduction of carbon dioxide to carbon monoxide.

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