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CN-121288857-B - Cobalt-nitrogen co-doped titanium dioxide/graphene composite photocatalyst and preparation method thereof

CN121288857BCN 121288857 BCN121288857 BCN 121288857BCN-121288857-B

Abstract

The invention relates to the field of photocatalytic materials, in particular to a cobalt-nitrogen co-doped titanium dioxide/graphene composite photocatalyst and a preparation method thereof, wherein the composite photocatalyst comprises, by weight, 10.0-15.0 parts of cobalt-nitrogen co-doped titanium dioxide, 1-3 mol% of cobalt element in the cobalt-nitrogen co-doped titanium dioxide, 0.5-2 mol% of nitrogen element in the cobalt-nitrogen co-doped titanium dioxide, 8-12% of oxygen vacancy concentration, 2.0-4.0 parts of Ti 3 C 2 T x MXanee and 0.5-1.5 parts of reduced graphene oxide, the cobalt-nitrogen co-doped titanium dioxide has an egg yolk-shell structure, the shell thickness is 10-20 nanometers, the gap layer thickness is 15-25 nanometers, and the light absorption range is expanded from an ultraviolet region to a visible light region of 500-650nm, so that the photocatalyst can efficiently utilize visible light.

Inventors

  • Guan Zeguang
  • XIAO YAN

Assignees

  • 樱辉(广东)环保科技有限公司

Dates

Publication Date
20260508
Application Date
20250729

Claims (10)

  1. 1. The cobalt-nitrogen co-doped titanium dioxide/graphene composite photocatalyst is characterized by comprising the following components in parts by weight: 10.0-15.0 parts of cobalt-nitrogen co-doped titanium dioxide, wherein cobalt element in the cobalt-nitrogen co-doped titanium dioxide is doped in a proportion of 1-3 mol%, nitrogen element is doped in a proportion of 0.5-2 mol%, and oxygen vacancy concentration is 8-12%; ti 3 C 2 T x MXene2.0-4.0 parts; 0.5-1.5 parts of reduced graphene oxide; the cobalt-nitrogen co-doped titanium dioxide has an egg yolk-shell structure, wherein the shell thickness is 10-20 nanometers, and the gap layer thickness is 15-25 nanometers.
  2. 2. The composite photocatalyst of claim 1, wherein the cobalt-nitrogen co-doped titania has a ratio of anatase phase to rutile phase of from 70:30 to 80:20.
  3. 3. The composite photocatalyst according to claim 1, wherein the composite photocatalyst has a specific surface area of 120-150m 2 /g and a pore volume of 0.3-0.5cm 3 /g.
  4. 4. The composite photocatalyst of claim 1, wherein the Ti 3 C 2 T x MXene platelets have a thickness of 1-3 nm and the reduced graphene oxide platelets have a thickness of 0.8-1.2 nm.
  5. 5. A method for preparing the composite photocatalyst according to any one of claims 1 to 4, characterized by comprising the steps of: (1) Preparing Ti 3 C 2 T x MXene nano-sheets; (2) Preparing reduced graphene oxide; (3) Preparing a cobalt-nitrogen co-doped titanium dioxide yolk-shell structure; (4) Performing oxygen vacancy engineering treatment; (5) Ti 3 C 2 T x MXene, cobalt-nitrogen co-doped titanium dioxide and reduced graphene oxide are integrated into a layered structure; (6) Freeze-drying preserves the hierarchical structure.
  6. 6. The method according to claim 5, wherein the specific process for preparing the Ti 3 C 2 T x MXene nanoplatelets in step (1) is: Reacting 5.0-10.0 parts of Ti 3 AlC 2 MAX phase powder with 3.0-6.0 parts of lithium fluoride in 30.0-50.0 parts of 9M hydrochloric acid solution at 20-25 ℃ for 24-36 hours for selective etching; washing with deionized water by repeated centrifugation until the pH value of the supernatant reaches 6-7; dispersing the washed multi-layer Ti 3 C 2 T x in 40.0-60.0 parts of dimethyl sulfoxide; ultrasonic treating in ice bath with 500-600W power for 3-4 hr; centrifuging to remove non-exfoliated particles, and collecting supernatant containing layered Ti 3 C 2 T x nano-sheets; After washing with deionized water at least 3 times by centrifugation, redispersion is carried out in 50.0-70.0 parts of deionized water.
  7. 7. The method according to claim 5, wherein the specific process for preparing reduced graphene oxide in step (2) is: Dispersing 0.5-5.0 parts of graphene oxide powder in 50.0-100.0 parts of deionized water; ultrasonic treating in ice bath with probe type ultrasonic instrument at 400-500W power for 1-2 hr; centrifuging to remove non-exfoliated particles, and collecting supernatant containing exfoliated graphene oxide nano sheets; adjusting the pH value of the graphene oxide dispersion liquid to 9-10 by using 0.1-0.5 part of ammonia water solution; Adding 0.1-0.3 part of L-ascorbic acid as a reducing agent; heating at 90-95 deg.C for 1-1.5 hr under nitrogen atmosphere; after washing by centrifugation at least 3 times, redispersed in 30.0-50.0 parts ethanol-water mixture.
  8. 8. The method according to claim 5, wherein the specific process for preparing the cobalt-nitrogen co-doped titanium dioxide yolk-shell structure in step (3) is as follows: Firstly preparing silicon dioxide template nanospheres, namely adding 3.0-5.0 parts of tetraethyl orthosilicate into 50.0-70.0 parts of absolute ethyl alcohol, stirring for 30 minutes, mixing 15.0-25.0 parts of deionized water with 10.0-15.0 parts of absolute ethyl alcohol and 3.0-5.0 parts of ammonia water, dropwise adding tetraethyl orthosilicate solution at 25-30 ℃, stirring for 4-6 hours, standing for 12-24 hours, collecting through centrifugation, washing with ethanol and deionized water alternately for at least 3 times, and drying at 60-70 ℃ for 10-12 hours; then preparing cobalt-nitrogen-titanium dioxide precursor solution, namely adding 10.0-15.0 parts of tetraisopropyl titanate into 40.0-60.0 parts of absolute ethyl alcohol in a nitrogen atmosphere, stirring for 30 minutes at 25 ℃, mixing 0.1-3.0 parts of cobalt nitrate hexahydrate and 0.5-5.0 parts of urea into 20.0-30.0 parts of deionized water, adding 1.0-3.0 parts of glacial acetic acid and stirring for 15-20 minutes, and dropwise adding cobalt-urea solution into the tetraisopropyl titanate solution at 15-20 ℃ in the nitrogen atmosphere; coating the silica nanospheres and forming a yolk-shell structure, namely dispersing 8.0-12.0 parts of silica nanospheres in 30.0-40.0 parts of ethanol, adding the dispersion into a titanium dioxide precursor sol, stirring for 2-3 hours, standing for 6-8 hours, collecting by centrifugation and washing with ethanol and deionized water alternately for at least 3 times, drying at 60-70 ℃ for 10-12 hours, heating to 450-500 ℃ at 2-3 ℃ per minute under an ammonia stream, and keeping for 2-3 hours for nitrogen doping and crystallization; Finally, the selective etching is carried out to form the yolk-shell structure, namely, nitrogen doped silicon dioxide@titanium dioxide particles are dispersed in 40.0-60.0 parts of deionized water, 5.0-10.0 parts of 2-3M sodium hydroxide solution is added, the mixture is heated to 60-70 ℃ and kept for 6-8 hours, the deionized water is collected through centrifugation and is repeatedly used for washing until the pH value of the supernatant reaches neutrality, and the supernatant is dried in vacuum at 70-80 ℃ for 10-12 hours.
  9. 9. The method of claim 5, wherein the oxygen vacancy engineering process in step (4) is performed by: Placing 5.0-7.0 parts of cobalt-nitrogen co-doped titanium dioxide yolk-shell structure particles into a plasma treatment chamber; vacuumizing to 1-5 Pa of basic pressure; argon is introduced at the flow of 10-15sccm to reach the working pressure of 10-20 Pa; generating a plasma using a radio frequency power of 13.56 megahertz, 50-80 watts; after 5-10 minutes of treatment, the mixture was cooled to room temperature under vacuum.
  10. 10. The method of claim 5, wherein the steps (5) and (6) integrate the components into a hierarchical structure and freeze-dry the components in the steps of: 3.0-5.0 parts of cobalt-nitrogen co-doped titanium dioxide yolk-shell structure particles subjected to plasma treatment are dispersed in 30.0-40.0 parts of ethanol; Adding Ti 3 C 2 T x MXene dispersion liquid dropwise at 25 ℃ to adjust the content of Ti 3 C 2 T x to 2.0-4.0 parts; Stirring for 3-4 hr, standing for 4-6 hr, centrifuging, collecting, and alternately washing with ethanol and deionized water for at least 3 times; dispersing 2.0-3.0 parts of Ti 3 C 2 T x @cobalt-nitrogen-titanium dioxide compound in 20.0-30.0 parts of ethanol-water mixed solution; Dropwise adding the reduced graphene oxide dispersion liquid, and adjusting the content to 0.5-1.5 parts; stirring for 2-3 hours, and then carrying out hydrothermal treatment at 120-150 ℃ for 4-6 hours; Rapidly freezing in liquid nitrogen for 5-10 minutes; Transferring to a freeze dryer to sublimate ice at-50 to-40 ℃ under 5-10 Pa vacuum for 24-36 hours; gradually increasing the temperature to 25 ℃ with maintaining the vacuum for 6-8 hours; and collecting the obtained hierarchical structure Ti 3 C 2 T x @ cobalt-nitrogen-titanium dioxide/reduced graphene oxide photocatalyst.

Description

Cobalt-nitrogen co-doped titanium dioxide/graphene composite photocatalyst and preparation method thereof Technical Field The invention relates to the field of photocatalytic materials, in particular to a cobalt-nitrogen co-doped titanium dioxide/graphene composite photocatalyst and a preparation method thereof. Background Titanium dioxide (TiO 2) is widely used in the field of photocatalysis due to its chemical stability, non-toxicity, low cost and high oxidation performance. However, pure TiO 2 has two main defects, namely that the pure TiO can only absorb ultraviolet light (accounting for less than 5% of solar spectrum) due to a wide band gap (3.2 eV), and that the quantum efficiency is reduced due to rapid recombination of photo-generated electron-hole pairs. To address these issues, researchers have proposed various modification strategies. In the prior art, nitrogen doped TiO 2 is widely studied. As Du Shiwen et al (Vis ible Light-Responsive N-Doped TiO2Photocatalysis:Synthesis,Char acterizations,and Applications.Transactions of Tianjin University,2021) report that nitrogen doping can introduce impurity levels above the valence band of TiO 2, extending the photoresponse range to the visible region, but the electron-hole recombination rate is still high. Metal doping is another strategy. The study of cobalt doped TiO 2 by Safeen et al (Enhancing the physical properties and photocatalytic activity of TiO2nanoparticles via cobalt doping.PMC,2022) shows that a proper amount of Co 2+ can introduce d-orbital energy level below the conduction band of TiO 2, effectively reducing the band gap, but a large amount of Co 2+ can also serve as a carrier recombination center. Chinese patent CN102500405A discloses a cerium-nitrogen-fluorine co-doped titanium dioxide photocatalyst and application thereof in degrading organic pollutants with visible light, the degradation efficiency of the organic pollutants under visible light reaches 75.62%, but the long-term stability is lacking. Compounding graphene with TiO 2 is a recent research hotspot. Tang Bo et al (Graphe ne Modified TiO2Composite Photocatalysts:Mechanism,Progress and Perspective.PMC,2018) reviewed graphene/TiO 2 composites, graphene can be used as an electron acceptor to promote charge separation, but simple compounding cannot effectively solve the problem of visible light absorption of TiO 2. The existing Ag/g-C 3N4/TiO2 composite photocatalyst (High efficiency photocataly tic degradation of indoor formaldehyde by Ag/g-C3N4/TiO2composit e catalyst with ZSM-5as the carrier.ScienceDirect,2021) has higher efficiency on formaldehyde degradation, but the application of noble metal Ag obviously increases the cost. A. Ashraf et al (Combination of sonochemical and freeze-drying methods for synthesis of graphene/Ag-doped TiO2nanocomposite：:A strategy to boost the photocatalytic performance via well distribu tion of nanoparticles between graphene sheets,2020) report that the graphene/Ag doped TiO 2 nanocomposite prepared by ultrasonic and freeze-drying methods effectively prevents agglomeration of graphene sheets, but the preparation process is complex and noble metal Ag is also used. At present, a photocatalysis system which integrates cobalt-nitrogen co-doping with graphene and MXene materials in a synergistic way is rarely reported, and particularly a photocatalyst with high efficiency, long stability and visible light response aiming at formaldehyde degradation is still a technical problem to be solved. Disclosure of Invention The invention aims to overcome the defects in the prior art and provide a cobalt-nitrogen co-doped titanium dioxide/graphene composite photocatalyst with high-efficiency visible light response, excellent formaldehyde degradation capability and long-term stability and a preparation method thereof. The cobalt-nitrogen co-doped titanium dioxide/graphene composite photocatalyst comprises, by weight, 10.0-15.0 parts of cobalt-nitrogen co-doped titanium dioxide, wherein cobalt element in the cobalt-nitrogen co-doped titanium dioxide is doped in a proportion of 1-3 mol%, nitrogen element is doped in a proportion of 0.5-2 mol%, the oxygen vacancy concentration is 8-12%, 3C2Tx MXene2.0-4.0 parts of Ti and 0.5-1.5 parts of reduced graphene oxide, and the cobalt-nitrogen co-doped titanium dioxide has a yolk-shell structure, wherein the shell thickness is 10-20 nanometers, and the gap layer thickness is 15-25 nanometers. Preferably, the ratio of anatase phase to rutile phase in the cobalt-nitrogen co-doped titanium dioxide is from 70:30 to 80:20. Preferably, the specific surface area of the composite photocatalyst is 120-150m 2/g, and the pore volume is 0.3-0.5cm 3/g. Preferably, the thickness of the Ti 3C2Tx MXene lamellar layer is 1-3 nanometers, and the thickness of the reduced graphene oxide lamellar layer is 0.8-1.2 nanometers. The invention also provides a preparation method of the composite photocatalyst, which comprises the following steps: (1)