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CN-122006762-A - Tungsten-doped molybdenum carbide heterojunction photo-thermal catalyst and preparation method and application thereof

CN122006762ACN 122006762 ACN122006762 ACN 122006762ACN-122006762-A

Abstract

The invention discloses a tungsten doped molybdenum carbide heterojunction photo-thermal catalyst and a preparation method and application thereof, wherein ammonium molybdate and ammonium tungstate are used as metal sources, aniline is used as an organic carbon source and a morphology guiding agent, a hybridization precursor is formed through self-assembly in a liquid phase, the hybridization precursor is prepared through high-temperature in-situ carbonization and reduction under inert or reducing atmosphere, the prepared catalyst maintains regular nanowire morphology, doping of tungsten atoms induces molybdenum carbide lattice distortion and partial crystalline phase transformation, an atomic-level coupled alpha-MoC/beta-Mo 2 C heterojunction is constructed, abundant molybdenum vacancy defects are generated in situ, excellent photo-thermal conversion efficiency, catalytic activity and CO selectivity are shown in a solar-driven reverse water gas conversion reaction, and an oxygen traction effect generated by utilizing the oxygen affinity characteristic of the tungsten atoms is utilized to stabilize surface active sites and improve oxidation resistance of the catalyst under a high-temperature photo-thermal condition. The preparation method is simple in preparation process and high in controllability, and an effective technical scheme is provided for solving the problem of poor stability of the non-noble metal carbide catalyst.

Inventors

  • LIU XIANGLEI
  • Zhou Luhao
  • XUAN YIMIN

Assignees

  • 南京航空航天大学

Dates

Publication Date
20260512
Application Date
20260206

Claims (10)

  1. 1. The tungsten doped molybdenum carbide heterojunction photo-thermal catalyst is characterized in that the catalyst is powder with a nanowire shape, and the microstructure of the catalyst is formed by stacking nano particles; The crystalline phase composition of the catalyst comprises cubic phase alpha-MoC and hexagonal phase beta-Mo 2 C, and an alpha-MoC/beta-Mo 2 C heterojunction is formed at the interface of the two phases; The crystal lattice of the catalyst is doped with tungsten atoms, and the surface of the catalyst is rich in molybdenum vacancy defects induced by tungsten doping.
  2. 2. The tungsten doped molybdenum carbide heterojunction photo-thermal catalyst of claim 1, wherein the diameter of the nanowire is 80-150 nm, and the specific surface area is 50-70 m 2 /g.
  3. 3. The tungsten doped molybdenum carbide heterojunction photo-thermal catalyst of claim 1, wherein the molar ratio of tungsten atoms to molybdenum in the catalyst is 0.05-0.2.
  4. 4. A method for preparing a tungsten doped molybdenum carbide heterojunction photo-thermal catalyst as claimed in any one of claims 1 to 3, comprising the steps of: preparing a precursor solution, namely dissolving a molybdenum source and a tungsten source in a solvent, uniformly mixing, adding organic amine, and stirring to form a mixed solution; dropwise adding acid into the mixed solution in the step (1) to adjust the pH value until a precipitate is generated, and then reacting under the constant temperature condition to obtain a tungsten-molybdenum-organic amine hybridization precursor; Step (3) drying treatment, namely filtering, washing and drying the hybridized precursor obtained in the step (2) to obtain precursor powder; And (4) high-temperature in-situ carbonization, namely placing the precursor powder in the step (3) in inert atmosphere or reducing atmosphere, heating to carbonization temperature at a specific heating rate and keeping for a certain time, and cooling to obtain the tungsten-doped molybdenum carbide heterojunction photo-thermal catalyst.
  5. 5. The method for preparing a tungsten-doped molybdenum carbide heterojunction photocatalyst according to claim 4, wherein in the step (1), the molybdenum source is ammonium molybdate tetrahydrate, the tungsten source is ammonium tungstate or ammonium metatungstate, the organic amine is aniline, and the solvent is deionized water; The ratio of the addition amount of the organic amine to the total molar amount of the metal source formed by the molybdenum source and the tungsten source is 1-3.5.
  6. 6. The method for preparing a tungsten-doped molybdenum carbide heterojunction photo-thermal catalyst according to claim 4, wherein the dropwise added acid in the step (2) is hydrochloric acid, and the pH value is adjusted to 3-4; the temperature of the constant-temperature reaction is 45-60 ℃, and the reaction time is 4-6 h.
  7. 7. The method for preparing a tungsten-doped molybdenum carbide heterojunction photo-thermal catalyst according to claim 4, wherein the drying temperature in the step (3) is 60-80 ℃.
  8. 8. The method for preparing a tungsten-doped molybdenum carbide heterojunction photo-thermal catalyst according to claim 4, wherein the heating rate in the step (4) is 1-5 ℃ per minute; the carbonization temperature is 600-800 ℃; The heat preservation time is 2-6 h.
  9. 9. Use of a tungsten doped molybdenum carbide heterojunction photo-thermal catalyst prepared by the preparation method of claim 4 in a solar driven reverse water gas shift reaction.
  10. 10. The use according to claim 9, wherein the active site of molybdenum carbide is protected by the traction of the tungsten oxide species on the surface of the catalyst to oxygen, and the efficient conversion of carbon dioxide and the long-period stable operation of the catalyst are realized under the high-temperature photo-thermal condition.

Description

Tungsten-doped molybdenum carbide heterojunction photo-thermal catalyst and preparation method and application thereof Technical Field The invention belongs to a tungsten-doped molybdenum carbide heterojunction photo-thermal catalyst, a preparation method and application thereof, and particularly relates to a tungsten-doped molybdenum carbide (W-doped MoxC) nanowire catalyst with oxidation resistance and high activity. Background The rapid increase of carbon dioxide emissions with excessive consumption of fossil fuels causes problems of greenhouse effect and climate change, and the utilization of renewable energy sources such as solar energy to drive the conversion of CO 2 into high added value chemicals is one of ideal ways to achieve the goal, wherein the Reverse Water Gas Shift (RWGS) reaction (CO 2+ H2→CO + H2 O) can not only convert CO 2 into synthesis gas (a mixture of CO and H 2), but also a key pre-step in the hydrocarbon fuel production process such as the subsequent fischer-tropsch synthesis. Compared with the traditional thermal catalysis technology, the photo-thermal catalysis technology can directly utilize the thermal effect and the photoelectron effect generated by sunlight to drive the reaction, among a plurality of photo-thermal catalysts, transition metal carbide (especially molybdenum carbide, mo x C) is considered as a potential material for replacing a noble metal catalyst due to the fact that the transition metal carbide has an electronic structure similar to noble metal (d-band center position is close to Pt), excellent conductivity and unique light absorption characteristics, and the traditional molybdenum carbide-based photo-thermal catalyst still faces serious technical challenges in practical application and is mainly characterized by poor high-temperature oxidation resistance, limited intrinsic activity and low light energy utilization rate. Because RWGS reaction is usually carried out at high temperature in an aqueous atmosphere, low-valence molybdenum species with strong affinity are extremely easy to deeply oxidize into inactive molybdenum oxide, so that irreversible deactivation of a catalyst is caused, which becomes the biggest obstacle for limiting industrial application of the catalyst, meanwhile, the conventional single crystal phase molybdenum carbide has single surface active site and limited adsorption and activation capability on CO 2 molecules, the electronic structure and the reaction energy barrier of the material are difficult to radically change through simple morphology regulation, and an effective charge separation mechanism is lacking in the material, so that photo-generated carriers are quickly compounded, and the advantage of photo-thermal synergistic catalysis is difficult to fully play. In order to overcome the defects, a novel molybdenum carbide catalyst with a special microstructure is needed to be developed, hetero atoms (such as tungsten) are introduced for doping, so that not only can the hetero atoms and the atomic radius difference of molybdenum be utilized to induce lattice distortion and phase change to construct a heterojunction to promote charge separation, but also a protective layer can be formed on the surface of the catalyst by utilizing the stronger oxygen-philic characteristic of tungsten element, so that the stability of molybdenum carbide active sites under severe reaction conditions is remarkably improved, and at present, related technical reports about in-situ construction of an alpha-MoC/beta-Mo 2 C hetero junction by utilizing tungsten doping and cooperative regulation of metal vacancies for efficient stable photothermal RWGS reaction are still less. Disclosure of Invention The invention aims to provide a tungsten doped molybdenum carbide heterojunction photo-thermal catalyst which realizes the three-in-one coordination of crystal phase regulation, vacancy engineering and oxidation resistance protection by doping tungsten (W) atoms, and the preparation method of the tungsten doped molybdenum carbide heterojunction photo-thermal catalyst which can remarkably improve the intrinsic activity and high-temperature stability of the catalyst. According to the technical scheme, the tungsten-doped molybdenum carbide heterojunction photo-thermal catalyst is powder with nanowire morphology, and the microstructure of the catalyst is formed by stacking nano particles; The crystalline phase composition of the catalyst comprises cubic phase alpha-MoC and hexagonal phase beta-Mo 2 C, and an alpha-MoC/beta-Mo 2 C heterojunction is formed at the interface of the two phases; The catalyst has tungsten (W) atoms doped in the crystal lattice and a surface rich in molybdenum (Mo) vacancy defects induced by tungsten doping. Further, the total spectrum light absorptivity of the catalyst in the wavelength range of 200-2500 nm is more than 90%; the diameter of the nanowire is 80-150 nm, and the specific surface area is 50-70 m 2/g. Further, the molar ratio of t