Novel Hollow N-doped KTaO3 Catalyst for Hydrogen Production via Water Splitting and Its Preparation Method

Abstract

The present application relates to a new type of hollow KTaON full water-splitting hydrogen catalyst and its preparation method. The preparation route takes polymer as template, adopts polyvinylamide with hollow morphology as structure template, first synthesizes hollow structure Ta2O5 intermediate; then the obtained Ta2O5 is fully mixed and ground with KCl at a molar ratio of 1.2-2:1, placed in a tube furnace for high temperature calcination, and finally the hollow structure KTaON photocatalytic material is prepared by programmed heating reaction under continuous flowing ammonia atmosphere. The catalyst can effectively promote the photocatalytic decomposition of water to produce hydrogen. The prepared hydrogen is a clean energy with excellent combustion performance, low density and zero carbon emission, which is an important path to replace traditional fossil energy and help achieve the goal of carbon neutralization.

Description

Technical Field

[0001] This invention relates to high-efficiency photocatalysis technology, particularly a novel hollow N-doped KTaO3 (KTaON) photocatalyst, which can efficiently photodegrade water to produce hydrogen, providing a new approach for energy conservation, environmental protection, and clean energy development. Background Technology

[0002] Addressing the dual challenges of the energy crisis and environmental protection that urgently need to be solved globally in the new century, this invention discloses a novel hollow KTaON water-splitting hydrogen production catalyst and its preparation method. The novel hollow KTaON water-splitting hydrogen production catalyst prepared by this invention has broad application prospects in the field of photocatalysis, possessing significant advantages such as a unique hollow morphology, a simple and easy preparation process, excellent long-term stability, and an environmentally friendly end-to-end synthesis route.

[0003] The following are the main methods reported to improve the photocatalytic efficiency of KTaON:

[0004] CN 103638958B reports a ZnS-CaTaO2N composite photocatalyst and its preparation method. The composite photocatalyst is formed by combining ZnS and CaTaO2N powders in a molar ratio of 5-15:1. This preparation method improves the spectral response range of the catalyst. Simultaneously, the formation of a heterojunction interface between ZnS and CaTaO2N effectively reduces the recombination of photogenerated electrons and holes, suppressing carrier recombination. The preparation method offers strong process controllability, low cost, and is suitable for large-scale production.

[0005] Existing research indicates that RTaON, as a typical alkali metal tantalum-based oxynitride, possesses a suitable visible light bandgap and a spectral response range covering the visible light region, demonstrating high application potential in photocatalytic water splitting for hydrogen production. Zhang et al. successfully prepared pure-phase photocatalytic powders using a molten salt-assisted nitriding process, optimizing the material's crystallinity and visible light absorption properties, confirming its ability to achieve highly efficient photocatalytic reactions under visible light, thus laying the foundation for the research on the preparation of KTaON-based materials. (Zou, Hai, et al. "Insight into the rate-determining step in photocatalytic Z-schemeoverall water splitting by employing a series of perovskite RTaON2 (R= Pr,Nd, Sm, and Gd) as model photocatalysts." Journal of the American Chemical Society 146.41 (2024): 28182-28189.)

[0006] Furthermore, Zhou et al. studied the effect of controllable nitridation of Ta2O5 in molten salt on photocatalytic performance. Tantalum-based oxynitrides are typical visible-light-responsive photocatalytic materials with a band gap adapted to the 420-600 nm visible light range, effectively utilizing solar energy. Combined with a high-temperature ammonia nitridation process, crystalline pure tantalum-based oxynitride powders can be prepared. Through morphology control (such as hollow or porous structures), the light absorption and carrier separation performance of the material can be further optimized. Selective etching can achieve precise transformation from bulk powder to hollow structures without damaging the material's crystalline structure, exhibiting strong process compatibility and providing methods and ideas for the preparation of new materials. (Zhou, Jing, et al. "Controllable nitridation of Ta2O5 in moltensalts for enhanced photocatalysis." International Journal of Minerals, Metallurgy and Materials 27.12 (2020): 1703-1710.)

[0007] However, the above methods still have certain defects and shortcomings. For example, although the ZnS-CaTaO2N composite photocatalyst can significantly improve the visible light absorption and photocatalytic activity of ZnS through the combination of the two components, it may cause a decrease in the rapid migration ability of photogenerated carriers, ultimately leading to a reduction in the photocatalytic hydrogen production performance of CaTaO2N through water splitting.

[0008] Compared to conventional photocatalyst preparation processes, this method for preparing hollow KTaON photocatalysts focuses on the precise and controllable adjustment of template size and morphology to directionally synthesize target catalytic materials with a predetermined hollow structure. Thanks to its unique hollow structure, this photocatalyst possesses a larger specific surface area and superior light absorption capacity compared to traditional solid catalytic systems. The high specific surface area exposes more abundant catalytic active sites, providing ample reaction space for the photocatalytic water splitting reaction. Furthermore, the unique light confinement effect of the hollow structure enhances the absorption and utilization of incident light, while its thin-walled structure significantly shortens the migration path of photogenerated carriers, substantially improving the migration and separation efficiency of photogenerated carriers.

[0009] In the field of photocatalytic water splitting for hydrogen production, KTaON is a promising visible-light-responsive catalytic material. Current performance optimization primarily relies on elemental doping modification, while controlling the microstructure of the bulk material particles represents another crucial and effective approach. Based on this, this project innovatively proposes a novel hollow-structured KTaON-based water splitting catalyst for hydrogen production and develops a corresponding controllable preparation process. This process uses a hollow polymer as a structural template. First, a Ta₂O₅ precursor with a specific hollow structure is synthesized via template-guided synthesis. Then, using this precursor as raw material, the target hollow-structured KTaON photocatalyst is obtained through a one-step ammonia calcination process. This provides a novel design approach and implementation path for the development of high-performance KTaON-based photocatalytic materials. Summary of the Invention

[0010] This invention provides a novel hollow KTaON water-splitting catalyst for hydrogen production and its preparation method. In the preparation process, a water-soluble polymer is used as a template, and hollow Ta₂O₅ is prepared using polyacrylamide (PAM). KCl and the prepared Ta₂O₅ are then mixed and ground at a specific molar ratio, and continuously heated in a tube furnace with a continuous flow of ammonia gas to obtain the hollow KTaON water-splitting catalyst. The hollow structure of this catalyst is beneficial for photon capture and photogenerated carrier transport, thus improving the utilization rate of light energy. The preparation method of the hollow KTaON photocatalyst provided by this invention includes the following steps:

[0011] 1. Preparation of hollow PAM polymers.

[0012] 2. Using hollow PAM polymers, Ta2O5 with a hollow structure was obtained.

[0013] 3. Mix and grind KCl and the prepared Ta2O5 at a certain molar ratio.

[0014] 4. Hollow KTaON photocatalyst was obtained by continuous heating in an ammonia gas stream.

[0015] The key to the preparation method provided by this invention lies in the organic combination of the use of polymer precursors and the formation of hollow structures. Using a hollow polymer as a template ensures that the final product possesses a hollow structure. This hollow structure plays a decisive role in improving photon capture efficiency and the transport of photogenerated carriers. The core step in constructing the hollow structure is the formation of hollow Ta₂O₅ using a specific preparation method with PAM polymers. The hollow structure, with its high porosity and channel structure, provides ideal support and a platform for subsequent catalyst preparation, thereby ensuring the final catalyst's performance in the total water splitting for hydrogen production.

[0016] This invention employs electrospun polyacrylamide (PAM) as the core template. This is because this template possesses a good hollow structure, allowing the final catalyst to have a hollow structure, thus improving photon capture efficiency and photogenerated carrier transport. Furthermore, PAM exhibits good structural and thermal stability during preparation, maintaining its morphology until the calcination process is complete. Therefore, using PAM polymer as a template, combined with a simple preparation method, is an effective means of preparing novel hollow-structured catalysts. Attached Figure Description

[0017] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings:

[0018] Figure 1 , Figure 2 This is a scanning electron microscope image of the hollow KTaON material prepared according to the embodiments of the present invention;

[0019] Figure 3 This is the BET diagram of the hollow KTaON material prepared according to the embodiments of the present invention;

[0020] Figure 4 This is a schematic diagram of the process for preparing hollow KTaON material according to an embodiment of the present invention. Detailed Implementation To better understand the present invention, it will be further described in detail below with reference to the accompanying drawings and embodiments. The following is a further description of the present invention, but not a limitation thereof. Example 1 The preparation method of the novel hollow KTaON water-splitting catalyst in the example includes the following steps: (1) Measure 0.2g Ta2O5 and 0.18g KOH and grind them in a crucible for 10min. Place the sample in a covered porcelain boat and heat it from room temperature to 673K ​​in air at a heating rate of 10℃ / min. After holding the temperature for 12 hours, cool it to room temperature. (2) Measure 120 ml of distilled water and place it in a beaker. Dissolve the sample and the prepared PAM in the beaker. After sonicating for 30 min, add sulfuric acid dropwise while stirring until pH=5. Observe that a white precipitate is formed. Filter, wash and dry. (3) Preparation of hollow KTaON powder by high-temperature calcination with ammonia: The prepared mixture was placed in an uncovered square porcelain boat and heated in air at a heating rate of 5℃ / min from room temperature to 873K. After holding at this temperature for 1 hour, it was cooled to room temperature to obtain hollow Ta2O5. KCl and the prepared Ta2O5 were mixed at the required molar ratio of 1.2:1. The mixture was placed in an uncovered square porcelain boat and heated in air at a heating rate of 10℃ / min from room temperature to 1173K. After holding at this temperature for 3 hours, it was cooled to room temperature. (4) After heating to 1173 K in a tube furnace, calcine for 0 to 5 hours, continuously introducing ammonia gas at a rate of 100 mL per minute. After heating, the obtained hollow KTaON powder is washed several times with deionized water and then dried in an oven. Example 2 The preparation method of the novel hollow KTaON water-splitting catalyst is described in the following steps: (1) Measure 0.4g Ta2O5 and 0.36g KOH and grind them in a crucible for 15min. Place the sample in a covered porcelain boat and heat it from room temperature to 723K in air at a heating rate of 10℃ / min. After holding the temperature for 12 hours, cool it to room temperature. (2) Measure 150 ml of distilled water and place it in a beaker. Dissolve the sample and the prepared PAM in the beaker. After sonicating for 40 min, add sulfuric acid dropwise while stirring until pH=5. Observe that a white precipitate is formed. Filter, wash and dry. (3) Preparation of hollow KTaON powder by high-temperature calcination with ammonia: The prepared mixture was placed in an uncovered square porcelain boat and heated in air at a heating rate of 5℃ / min from room temperature to 873K. After holding at this temperature for 1 hour, it was cooled to room temperature to obtain hollow Ta2O5. KCl and the prepared Ta2O5 were mixed at the required molar ratio of 1.5:1. The mixture was placed in an uncovered square porcelain boat and heated in air at a heating rate of 10℃ / min from room temperature to 1173K. After holding at this temperature for 3 hours, it was cooled to room temperature. (4) After heating to 1173 K in a tube furnace, calcine for 0-5 hours while continuously introducing ammonia gas at a rate of 120 mL per minute. After heating, the resulting hollow KTaON powder is washed several times with deionized water and then dried in an oven. Example 3 The preparation method of the novel hollow KTaON water-splitting catalyst is described in the following steps: (1) Measure 0.4g Ta2O5 and 0.36g KOH and grind them in a crucible for 15min. Place the sample in a covered porcelain boat and heat it from room temperature to 823K in air at a heating rate of 10℃ / min. After holding the temperature for 12 hours, cool it to room temperature. (2) Measure 150 ml of distilled water and place it in a beaker. Dissolve the sample and the prepared PAM in the beaker. After sonicating for 40 min, add sulfuric acid dropwise while stirring until pH=5. Observe that a white precipitate is formed. Filter, wash and dry. (3) Preparation of hollow KTaON powder by high-temperature calcination with ammonia: The prepared mixture was placed in an uncovered square porcelain boat and heated in air at a heating rate of 5℃ / min from room temperature to 873K. After holding at this temperature for 2 hours, it was cooled to room temperature to obtain hollow Ta2O5. KCl and the prepared Ta2O5 were mixed at the required molar ratio of 2:1. The mixture was placed in an uncovered square porcelain boat and heated in air at a heating rate of 10℃ / min from room temperature to 1173K. After holding at this temperature for 4 hours, it was cooled to room temperature. (4) After heating to 1173 K in a tube furnace, calcine for 0-5 hours, continuously introducing ammonia gas at a rate of 150 mL per minute. After heating, the obtained hollow KTaON powder is washed several times with deionized water and then dried in an oven.

Claims

1. A novel hollow N-doped KTaO3 catalyst for hydrogen production through water splitting and its preparation method, the steps of which include: Hollow-structured KTaO3 materials were prepared using the water-soluble polymer polyacrylamide (PAM). The prepared K8[Ta6O] 19 Dissolve and add H2SO4 dropwise to precipitate on the surface of the polymer structure: Hollow Ta2O5 was obtained by heating the polymer template at 400 ~ 450℃; KCl and the prepared Ta2O5 were mixed and ground in a certain molar ratio; Hollow N-doped KTaO3 catalyst was obtained by continuous heating in an ammonia gas stream.

2. The hollow N-doped KTaO3 photocatalyst according to claim 1, wherein the molar ratio of KCl to Ta2O5 is 1.2~2:1 during the preparation process.

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