CN113578297B - Oxygen-terminated monolayer titanium carbide composite titanium dioxide photocatalyst and preparation method thereof - Google Patents
Oxygen-terminated monolayer titanium carbide composite titanium dioxide photocatalyst and preparation method thereof Download PDFInfo
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- CN113578297B CN113578297B CN202110998693.8A CN202110998693A CN113578297B CN 113578297 B CN113578297 B CN 113578297B CN 202110998693 A CN202110998693 A CN 202110998693A CN 113578297 B CN113578297 B CN 113578297B
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- 239000002131 composite material Substances 0.000 title claims abstract description 34
- MTPVUVINMAGMJL-UHFFFAOYSA-N trimethyl(1,1,2,2,2-pentafluoroethyl)silane Chemical compound C[Si](C)(C)C(F)(F)C(F)(F)F MTPVUVINMAGMJL-UHFFFAOYSA-N 0.000 title claims abstract description 33
- 239000004408 titanium dioxide Substances 0.000 title claims abstract description 22
- 238000002360 preparation method Methods 0.000 title abstract description 12
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- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 2
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- 229910014033 C-OH Inorganic materials 0.000 description 1
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- NIPNSKYNPDTRPC-UHFFFAOYSA-N N-[2-oxo-2-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)ethyl]-2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidine-5-carboxamide Chemical compound O=C(CNC(=O)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)N1CC2=C(CC1)NN=N2 NIPNSKYNPDTRPC-UHFFFAOYSA-N 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
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- JEUXZUSUYIHGNL-UHFFFAOYSA-N n,n-diethylethanamine;hydrate Chemical compound O.CCN(CC)CC JEUXZUSUYIHGNL-UHFFFAOYSA-N 0.000 description 1
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- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J35/00—Catalysts, in general, characterised by their form or physical properties
- B01J35/30—Catalysts, in general, characterised by their form or physical properties characterised by their physical properties
- B01J35/39—Photocatalytic properties
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
- B01J21/06—Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
- B01J21/063—Titanium; Oxides or hydroxides thereof
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- B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
- B01J27/20—Carbon compounds
- B01J27/22—Carbides
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- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/08—Heat treatment
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Abstract
The invention discloses an oxygen-terminated monolayer titanium carbide composite titanium dioxide photocatalyst and a preparation method thereof, belonging to the technical field of nanocomposite materials and photocatalysts. The invention firstly adopts an in-situ hydrothermal oxidation method to oxidize Ti in single layer 3 C 2 T x Edge-grown (001) face-exposed TiO 2 The method comprises the steps of carrying out a first treatment on the surface of the Then increase Ti through annealing treatment 3 C 2 T x Content of surface oxygen groups; obtaining Ti 3 C 2 O/(001)TiO 2 Namely the oxygen end capped monolayer titanium carbide composite titanium dioxide photocatalyst. The oxygen-capped monolayer titanium carbide composite titanium dioxide photocatalyst prepared by the invention improves the existing Ti 3 C 2 T x Photocatalytic properties of the material.
Description
Technical Field
The invention belongs to the technical field of nano composite materials and photocatalysts, and relates to an oxygen-terminated monolayer titanium carbide composite titanium dioxide photocatalyst and a preparation method thereof.
Background
With the increasing consumption of energy and environmental problems, the global demand for green energy to replace fossil fuel combustion is rapidly growing. The hydrogen as fuel has the advantages of high combustion heat value, no pollution and the like, and accelerates the development of hydrogen energy to become a new focus of energy conversion in China. The photocatalyst technology can be used for converting solar energy into sustainable hydrogen energy in an environment-friendly and efficient way.
However, the low solar energy utilization efficiency and the ultra-fast recombination of photo-generated electrons and holes greatly obstruct the application prospect of the traditional photocatalysis hydrogen production. In recent years, a breakthrough has been sought in the development of high-efficiency photocatalysts, which has become a research hotspot in the field of energy conversion.
Mxenes is a generic term for a class of two-dimensional transition metal carbides, nitrides or carbonitrides. Has hydrophobicity, metallic conductivity and excellent electrical, optical, mechanical and thermodynamic properties. Ti (Ti) 3 C 2 T x As one of the most widely studied Mxene materials, one can etch Ti by chemical etching 3 AlC 2 The prepared product has wide application prospect in the field of photocatalysis. Recent research progress shows that Ti 3 C 2 T x The photocatalytic ability of (2) can be controlled substantially by adjusting the surface groups. Wherein an increase in the number of oxygen groups is believed to be effective in enhancing its photocatalytic performance. However, this type of catalyst generally does not achieve good activity. This is mainly due to Ti 3 C 2 T x Electrons and holes cannot be generated by photoexcitation, electrons can only be accepted, oxidation-reduction capability is weakened, and separation of photogenerated electrons and holes is incomplete. Meanwhile, due to the lack of single-layer Ti 3 C 2 T x In the systematic research of the field of photocatalytic hydrogen production, the relation between the characteristics of morphology, surface functional groups and the like and the photocatalytic hydrogen production activity is not clear. This greatly hinders Ti 3 C 2 T x Research and exploration in the field of photocatalysis and efficient design of MXenes-based photocatalytic materials.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention aims to provide an oxygen-terminated single-layer titanium carbide composite titanium dioxide photocatalyst and a preparation method thereof, which improve the prior Ti 3 C 2 T x Photocatalytic properties of the material.
In order to achieve the above purpose, the invention is realized by adopting the following technical scheme:
the invention discloses a preparation method of an oxygen-terminated monolayer titanium carbide composite titanium dioxide photocatalyst, which comprises the steps of firstly preparing a monolayer Ti by an in-situ hydrothermal oxidation method 3 C 2 T x (Edge)Growth of (001) face exposed TiO 2 The method comprises the steps of carrying out a first treatment on the surface of the Then increase Ti through annealing treatment 3 C 2 T x Content of surface oxygen groups; obtaining Ti 3 C 2 O/(001)TiO 2 Namely the oxygen end capped monolayer titanium carbide composite titanium dioxide photocatalyst.
Preferably, the method comprises the following steps: to single layer Ti 3 C 2 T x And NaBF 4 After being added into dilute HCl for dissolution, the in-situ hydrothermal oxidation reaction is carried out to realize the single-layer Ti 3 C 2 T x Edge-grown (001) face-exposed TiO 2 The method comprises the steps of carrying out a first treatment on the surface of the After the reaction is finished, cooling the system to room temperature, and collecting a product; washing, centrifuging and drying the obtained product to obtain uniformly dispersed powder; annealing the obtained powder by heating to obtain Ti 3 C 2 T x Controllable oxidation of surface groups.
Further preferably, a single layer of Ti 3 C 2 T x The reaction charging ratio of sodium fluoborate and dilute HCl is 0.1-0.3 g: 0.165-0.495 g: 40-60 mL; wherein the concentration of the dilute HCl is 0.5-2 mol/L.
Preferably, the temperature of the in-situ hydrothermal oxidation reaction is 120-200 ℃ and the reaction time is 8-20 hours.
Preferably, the annealing treatment is carried out at a temperature of 250 to 450 ℃ for 0.5 to 2 hours.
Preferably, a single layer of Ti 3 C 2 T x The method comprises the following steps: uniformly mixing LiF and concentrated HCl to obtain etching solution; ti is mixed with 3 AlC 2 Removing the Al layer in the etching solution by chemical etching, and washing to neutrality after etching to obtain multi-layer Ti 3 C 2 T x The method comprises the steps of carrying out a first treatment on the surface of the The obtained multi-layer Ti 3 C 2 T x Dissolving in water, and carrying out ultrasonic treatment in an inert atmosphere for layering to obtain a dispersion system; centrifuging the obtained dispersion, collecting upper suspension, and lyophilizing the upper suspension to obtain single-layer Ti 3 C 2 T x 。
Further preferably, liF, concentrated HCl and Ti 3 AlC 2 The reaction feeding ratio of (1-3 g): 40-70 mL: 1-3 g; wherein the concentration of the concentrated HCl is 9-12 mol/L.
Further preferably, the operating parameters of the chemical etching include: under the stirring condition, the etching temperature is 30-40 ℃ and the etching time is 24-48 hours;
further preferably, the resulting multilayer Ti 3 C 2 T x After dissolving in water, the mixture is subjected to ultrasonic treatment for 1.5 to 3 hours in an inert atmosphere to carry out layering.
The invention discloses an oxygen-terminated monolayer titanium carbide composite titanium dioxide photocatalyst prepared by the preparation method.
Compared with the prior art, the invention has the following beneficial effects:
the invention discloses a preparation method of an oxygen-terminated single-layer titanium carbide composite titanium dioxide photocatalyst, which has obvious advantages compared with the prior art and aims at improving single Ti 3 C 2 T x The material has weak visible light response and fast carrier recombination, realizes triple controllable modification by using a simple preparation method, and prepares Ti without adding extra titanium source 3 C 2 O/(001)TiO 2 Novel photocatalysts. In situ oxidation of Ti by hydrothermal method 3 C 2 T x Formation of active face exposed TiO 2 Constructing a schottky heterojunction further improves the separation of holes and electrons and increases Ti 3 C 2 T x Active oxygen groups on the surface promote the photocatalytic reaction. In the experiment of preparing hydrogen by photolysis of water, under the irradiation of light, ti is excited 3 C 2 O generates electrons and holes, and (001) TiO 2 As the acceptor of the photoexcited semiconductor carrier, electrons can be smoothly transferred, the recombination of electrons and holes can be slowed down or inhibited, and the photocatalysis performance can be enhanced.
The invention discloses an oxygen-terminated single-layer titanium carbide composite titanium dioxide photocatalyst prepared by the preparation method, wherein TiO is exposed in the catalyst 2 The high activity crystal face of the (B) can effectively improve the inherent defects thereof, and has great application in improving the photocatalytic activityPotential. At the same time Ti 3 C 2 T x With TiO 2 The Schottky heterojunction structure formed between the two can promote the separation effect of holes and electrons, further promote the performance of photocatalysis reaction, and successfully improve single Ti by adjusting surface functional groups, exposing high-activity surfaces and controlling triple controllable modification of structure size 3 C 2 T x Is used for the photocatalytic activity of the catalyst.
Drawings
FIG. 1 is an SEM image of an oxygen-terminated single-layer titanium carbide composite titania photocatalyst according to the present invention;
FIG. 2 is a TEM image of an oxygen-terminated single-layer titanium carbide composite titania photocatalyst according to the present invention; wherein (a) is Ti 3 C 2 O and (001) TiO 2 A topography of the connection, (b) a partial enlargement of (a), and (c) Ti 3 C 2 O and (001) TiO 2 Is a top view of the connection;
FIG. 3 is an XPS diagram of an oxygen-terminated single-layer titanium carbide composite titania photocatalyst according to the present invention; wherein (a) is Ti 3 C 2 T x And Ti is 3 C 2 O/(001)TiO 2 Broad spectrum of (b) is Ti 3 C 2 T x And Ti is 3 C 2 O/(001)TiO 2 C1s spectrum of (C) is Ti 3 C 2 T x And Ti is 3 C 2 O/(001)TiO 2 (d) is Ti 2p spectrum of Ti 3 C 2 T x And Ti is 3 C 2 O/(001)TiO 2 O1s spectrum of (c);
FIG. 4 is a schematic illustration of N of an oxygen-capped monolayer titanium carbide composite titania photocatalyst and a sample prior to modification in accordance with the present invention 2 Adsorption-desorption curves and corresponding BET surface areas;
FIG. 5 is a graph showing diffuse reflection of ultraviolet and visible light of an oxygen-terminated single-layer titanium carbide composite titanium dioxide photocatalyst according to the present invention; wherein, (a) is a UV-vis DRS spectrogram, and (b) is a corresponding forbidden bandwidth;
FIG. 6 is a graph comparing hydrogen production performance of an oxygen-terminated single-layer titanium carbide composite titanium dioxide photocatalyst according to the invention; wherein, (a) is the photocatalytic hydrogen production amount, and (b) is a photocatalytic hydrogen production rate comparison chart;
FIG. 7 is a graph comparing the photoelectrochemical properties of an oxygen-capped monolayer titanium carbide composite titania photocatalyst according to the present invention; wherein (a) is a linear sweep voltammogram and (b) is Ti 3 C 2 T x (c) is (001) TiO 2 The mort-schottky curve (d) is the electrochemical impedance spectrum and (e) is the transient photocurrent response curve.
Detailed Description
In order that those skilled in the art will better understand the present invention, a technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in which it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without making any inventive effort, shall fall within the scope of the present invention.
It should be noted that the terms "first," "second," and the like in the description and the claims of the present invention and the above figures are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate such that the embodiments of the invention described herein may be implemented in sequences other than those illustrated or otherwise described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
The invention provides a simple and effective preparation method of a novel photocatalyst for preparing oxygen-terminated single-layer titanium carbide composite titanium dioxide, which aims to improve Ti 3 C 2 T x The photocatalytic performance of the material provides a reference method.
The invention is described inOxygen-terminated monolayer titanium carbide composite titanium dioxide photocatalyst, and oxygen-terminated monolayer Ti 3 C 2 T x TiO exposed with (001) face 2 Composition of Ti in single layer by in situ hydrothermal oxidation method 3 C 2 T x Edge-grown (001) face-exposed TiO 2 Increasing Ti using muffle furnace annealing 3 C 2 T x Content of surface oxygen groups. Triple controllable modification to improve single Ti by adjusting surface functional groups, exposing high active surface and controlling structure size 3 C 2 T x Is used for the photocatalytic activity of the catalyst.
The preparation method comprises the following steps:
(1)Ti 3 AlC 2 is a chemical etching of: a quantity of LiF and concentrated HCl were added to the PTFE vessel and dissolved with stirring. Thereafter, ti is added to 3 AlC 2 Slowly adding the solution, and under the stirring condition, etching at 30-40 ℃ for 24-48 hours; and completely removing the Al layer by chemical etching, and centrifugally washing to be neutral by using ultrapure water.
Wherein LiF, concentrated HCl and Ti 3 AlC 2 The reaction feeding ratio of (1-3 g): 40-70 mL: 1-3 g; the concentration of the concentrated HCl is 9-12 mol/L.
(2) Single layer Ti 3 C 2 T x Is prepared from the following steps: subsequently, the multi-layer Ti is 3 C 2 T x Dissolving in ultrapure water, and carrying out ultrasonic treatment for 1.5-3 hours in an inert atmosphere to carry out layering. Centrifuging to collect upper dark green suspension, and lyophilizing to obtain single layer Ti 3 C 2 T x 。
(3)Ti 3 C 2 O/(001)TiO 2 Is prepared from the following steps: by addition of NaBF 4 Adjusting TiO 2 Is a crystal plane exposed. An amount of single layer Ti 3 C 2 T x And NaBF 4 Add to dilute HCl and dissolve with thorough stirring. And transferring the solution into a polytetrafluoroethylene container, heating and reacting for a period of time, and performing in-situ hydrothermal oxidation reaction at the temperature of 120-200 ℃ for 8-20 hours. After the system is cooled to room temperature, the sample is washed, centrifuged and dried overnight to obtainUniformly dispersed powder Ti 3 C 2 T x /(001)TiO 2 . Then, the obtained powder is heated and kept in a muffle furnace for annealing treatment to realize Ti 3 C 2 T x Controllable oxidation of surface groups to obtain Ti 3 C 2 O/(001)TiO 2 。
Wherein, single layer Ti 3 C 2 T x The reaction charging ratio of sodium fluoborate and dilute HCl is 0.1-0.3 g: 0.165-0.495 g: 40-60 mL; the concentration of the dilute HCl is 0.5-2 mol/L.
Wherein the temperature of the annealing treatment is 250-450 ℃ and the annealing time is 0.5-2 hours; the temperature rising rate is 5 ℃/min.
The present invention will be further illustrated with reference to specific examples, which are not intended to limit the scope of the invention.
Example 1
25mL of 9mol/L concentrated hydrochloric acid was weighed into a 100mL PTFE container, and 1g of LiF powder was weighed and dissolved in the container, and magnetic stirring was continued for 30 minutes. Thereafter, 1g of Ti 3 AlC 2 Slowly add to the above solution. Because a large amount of heat is released during the addition process, to prevent Ti 3 AlC 2 Oxidized and the entire addition process lasted 5 minutes. Ti (Ti) 3 AlC 2 After all the components are added, the mixture is sealed by a sealing film. Stirring was continued at 35 ℃ for 36 hours to completely etch away the Al layer. After etching, the supernatant is neutral by centrifugal washing with ultrapure water for 6 to 8 times.
After the last washing, the product was dissolved again in 50mL of ultra-pure water and was subjected to ice water ultrasonic delamination for 1.5 hours under the protection of argon. Centrifuging at 3500rpm for 1 hr after ultrasonic treatment, collecting upper dark green suspension, and lyophilizing overnight to obtain single-layer Ti 3 C 2 T x And (3) a sample.
0.2g of single-layer Ti is weighed 3 C 2 T x And 0.33g of sodium fluoroborate was added to 40mL of 1mol/L HCl and kept stirring for 30 minutes. Thereafter, the above solution was transferred to a polytetrafluoroethylene container and heated at 160℃for 12 hours. After the system is cooled to room temperature, the sample is washed, centrifuged and dried at 60 ℃ overnight to obtainUniformly dispersed powder Ti 3 C 2 T x /(001)TiO 2 。
The resulting powder was heated to 350℃in a muffle furnace at a rate of 5℃per minute and maintained for 1 hour to achieve Ti 3 C 2 T x Controllable oxidation of surface groups to obtain Ti 3 C 2 O/(001)TiO 2 。
Example 2
50mL of 9mol/L concentrated hydrochloric acid was weighed into a 100mL PTFE container, and 2g of LiF powder was weighed and dissolved in the container, and magnetic stirring was continued for 30 minutes. Thereafter, 2g of Ti 3 AlC 2 Slowly add to the above solution. Because a large amount of heat is released during the addition process, to prevent Ti 3 AlC 2 Oxidized and the entire addition process lasted 5 minutes. Ti (Ti) 3 AlC 2 After all the components are added, the mixture is sealed by a sealing film. Stirring was continued at 30 ℃ for 48 hours to completely etch away the Al layer. After etching, the supernatant is neutral by centrifugal washing with ultrapure water for 6 to 8 times.
After the last washing, the product was dissolved again in 50mL of ultra-pure water and was subjected to ice water ultrasonic delamination for 1.5 hours under the protection of argon. Centrifuging at 3500rpm for 1 hr after ultrasonic treatment, collecting upper dark green suspension, and lyophilizing overnight to obtain single-layer Ti 3 C 2 T x And (3) a sample.
0.1g of single-layer Ti is weighed 3 C 2 T x And 0.165g sodium fluoroborate was added to 40mL 1mol/L HCl and kept stirring for 30 minutes. Thereafter, the above solution was transferred to a polytetrafluoroethylene container and heated at 120℃for 20 hours. After the system is cooled to room temperature, washing the sample, centrifuging and drying at 60 ℃ overnight to obtain evenly dispersed powder Ti 3 C 2 T x /(001)TiO 2 。
The resulting powder was heated to 450 ℃ in a muffle furnace at a rate of 5 ℃/min and held for 0.5 hours to achieve Ti 3 C 2 T x Controllable oxidation of surface groups to obtain Ti 3 C 2 O/(001)TiO 2 。
Example 3
60mL of 12mol/L concentrated hydrochloric acid is measured to 100mLIn a PTFE vessel, 3g of LiF powder was weighed again and dissolved in the vessel, and magnetic stirring was continued for 30 minutes. Thereafter, 3g of Ti 3 AlC 2 Slowly add to the above solution. Because a large amount of heat is released during the addition process, to prevent Ti 3 AlC 2 Oxidized and the entire addition process lasted 5 minutes. Ti (Ti) 3 AlC 2 After all the components are added, the mixture is sealed by a sealing film. Stirring was continued at 40 ℃ for 24 hours to completely etch away the Al layer. After etching, the supernatant is neutral by centrifugal washing with ultrapure water for 6 to 8 times.
After the last washing, the product was dissolved again in 50mL of ultra-pure water and was subjected to ice water ultrasonic delamination for 1.5 hours under the protection of argon. Centrifuging at 3500rpm for 1 hr after ultrasonic treatment, collecting upper dark green suspension, and lyophilizing overnight to obtain single-layer Ti 3 C 2 T x And (3) a sample.
0.3g of single-layer Ti is weighed 3 C 2 T x And 0.495g of sodium fluoroborate was added to 60mL of 2mol/L HCl and kept stirring for 30 minutes. Thereafter, the above solution was transferred to a polytetrafluoroethylene container and heated at 200℃for 8 hours. After the system is cooled to room temperature, washing the sample, centrifuging and drying at 60 ℃ overnight to obtain evenly dispersed powder Ti 3 C 2 T x /(001)TiO 2 。
The resulting powder was heated to 250℃in a muffle furnace at a rate of 5℃per minute and maintained for 2 hours to achieve Ti 3 C 2 T x Controllable oxidation of surface groups to obtain Ti 3 C 2 O/(001)TiO 2 。
Example 4
25mL of 12mol/L concentrated hydrochloric acid was weighed into a 100mL PTFE container, and 1g of LiF powder was weighed and dissolved in the container, and magnetic stirring was continued for 30 minutes. Thereafter, 1g of Ti 3 AlC 2 Slowly add to the above solution. Because a large amount of heat is released during the addition process, to prevent Ti 3 AlC 2 Oxidized and the entire addition process lasted 5 minutes. Ti (Ti) 3 AlC 2 After all the components are added, the mixture is sealed by a sealing film. Stirring was continued at 40 ℃ for 24 hours to completely etch away the Al layer. Centrifugally washing the supernatant with ultrapure water for 6-8 times after etchingIs neutral.
After the last washing, the product was dissolved again in 50mL of ultra-pure water and was subjected to ice water sonication for 3 hours under argon protection for delamination. Centrifuging at 3500rpm for 1 hr after ultrasonic treatment, collecting upper dark green suspension, and lyophilizing overnight to obtain single-layer Ti 3 C 2 T x And (3) a sample.
0.2g of single-layer Ti is weighed 3 C 2 T x And 0.33g of sodium fluoroborate was added to 40mL of 1mol/L HCl and kept stirring for 30 minutes. Thereafter, the above solution was transferred to a polytetrafluoroethylene container and heated at 120℃for 20 hours. After the system is cooled to room temperature, washing the sample, centrifuging and drying at 60 ℃ overnight to obtain evenly dispersed powder Ti 3 C 2 T x /(001)TiO 2 。
The resulting powder was heated to 450 ℃ in a muffle furnace at a rate of 5 ℃/min and held for 0.5 hours to achieve Ti 3 C 2 T x Controllable oxidation of surface groups to obtain Ti 3 C 2 O/(001)TiO 2 。
Example 5
60mL of 9mol/L concentrated hydrochloric acid was weighed into a 100mL PTFE container, and 3g of LiF powder was weighed and dissolved in the container, and magnetic stirring was continued for 30 minutes. Thereafter, 3g of Ti 3 AlC 2 Slowly add to the above solution. Because a large amount of heat is released during the addition process, to prevent Ti 3 AlC 2 Oxidized and the entire addition process lasted 5 minutes. Ti (Ti) 3 AlC 2 After all the components are added, the mixture is sealed by a sealing film. Stirring was continued at 30 ℃ for 48 hours to completely etch away the Al layer. After etching, the supernatant is neutral by centrifugal washing with ultrapure water for 6 to 8 times.
After the last washing, the product was dissolved again in 50mL of ultra-pure water and was subjected to ice water sonication for 2 hours under argon protection for delamination. Centrifuging at 3500rpm for 1 hr after ultrasonic treatment, collecting upper dark green suspension, and lyophilizing overnight to obtain single-layer Ti 3 C 2 T x And (3) a sample.
0.3g of single-layer Ti is weighed 3 C 2 T x And 0.495g of sodium fluoroborate was added to 60mL of 1mol/L HClAnd kept stirring for 30 minutes. Thereafter, the above solution was transferred to a polytetrafluoroethylene container and heated at 160℃for 12 hours. After the system is cooled to room temperature, washing the sample, centrifuging and drying at 60 ℃ overnight to obtain evenly dispersed powder Ti 3 C 2 T x /(001)TiO 2 。
The resulting powder was heated to 350℃in a muffle furnace at a rate of 5℃per minute and maintained for 1 hour to achieve Ti 3 C 2 T x Controllable oxidation of surface groups to obtain Ti 3 C 2 O/(001)TiO 2 。
Example 6
50mL of 12mol/L concentrated hydrochloric acid was weighed into a 100mL PTFE container, and 2g of LiF powder was weighed and dissolved in the container, and magnetic stirring was continued for 30 minutes. Thereafter, 2g of Ti 3 AlC 2 Slowly add to the above solution. Because a large amount of heat is released during the addition process, to prevent Ti 3 AlC 2 Oxidized and the entire addition process lasted 5 minutes. Ti (Ti) 3 AlC 2 After all the components are added, the mixture is sealed by a sealing film. Stirring was continued at 35 ℃ for 36 hours to completely etch away the Al layer. After etching, the supernatant is neutral by centrifugal washing with ultrapure water for 6 to 8 times.
After the last washing, the product was dissolved again in 50mL of ultra-pure water and was subjected to ice water sonication for 2 hours under argon protection for delamination. Centrifuging at 3500rpm for 1 hr after ultrasonic treatment, collecting upper dark green suspension, and lyophilizing overnight to obtain single-layer Ti 3 C 2 T x And (3) a sample.
0.1g of single-layer Ti is weighed 3 C 2 T x And 0.165g sodium fluoroborate was added to 50mL 1mol/L HCl and kept stirring for 30 minutes. Thereafter, the above solution was transferred to a polytetrafluoroethylene container and heated at 120℃for 20 hours. After the system is cooled to room temperature, washing the sample, centrifuging and drying at 60 ℃ overnight to obtain evenly dispersed powder Ti 3 C 2 T x /(001)TiO 2 。
The resulting powder was heated to 450 ℃ in a muffle furnace at a rate of 5 ℃/min and held for 0.5 hours to achieve Ti 3 C 2 T x Controllable oxidation of surface groups to obtain Ti 3 C 2 O/(001)TiO 2 。
Example 7
40mL of 10mol/L concentrated hydrochloric acid was weighed into a 100mL PTFE container, and 2.5g of LiF powder was weighed and dissolved in the container, and magnetic stirring was continued for 30 minutes. Thereafter, 2.5g of Ti 3 AlC 2 Slowly add to the above solution. Because a large amount of heat is released during the addition process, to prevent Ti 3 AlC 2 Oxidized and the entire addition process lasted 5 minutes. Ti (Ti) 3 AlC 2 After all the components are added, the mixture is sealed by a sealing film. Stirring was continued at 35 ℃ for 30 hours to completely etch away the Al layer. After etching, the supernatant is neutral by centrifugal washing with ultrapure water for 6 to 8 times.
After the last washing, the product was dissolved again in 50mL of ultra-pure water and was subjected to ice water sonication for 2.5 hours under argon protection for delamination. Centrifuging at 3500rpm for 1 hr after ultrasonic treatment, collecting upper dark green suspension, and lyophilizing overnight to obtain single-layer Ti 3 C 2 T x And (3) a sample.
0.15g of single-layer Ti is weighed 3 C 2 T x And 0.247g of sodium fluoroborate was added to 55mL of 0.5mol/L HCl and stirred for 30 minutes. Thereafter, the above solution was transferred to a polytetrafluoroethylene container and heated at 180℃for 10 hours. After the system is cooled to room temperature, washing the sample, centrifuging and drying at 60 ℃ overnight to obtain evenly dispersed powder Ti 3 C 2 T x /(001)TiO 2 。
The resulting powder was heated to 300℃in a muffle furnace at a rate of 5℃per minute and maintained for 1.5 hours to effect Ti 3 C 2 T x Controllable oxidation of surface groups to obtain Ti 3 C 2 O/(001)TiO 2 。
Example 8
70mL of 11mol/L concentrated hydrochloric acid was weighed into a 100mL PTFE container, and 1.5g of LiF powder was weighed and dissolved in the container, and magnetic stirring was continued for 30 minutes. Thereafter, 1.5g of Ti 3 AlC 2 Slowly add to the above solution. Because a large amount of heat is released during the addition process, to prevent Ti 3 AlC 2 Is oxidizedThe entire addition process lasted 5 minutes. Ti (Ti) 3 AlC 2 After all the components are added, the mixture is sealed by a sealing film. Stirring was continued at 35 ℃ for 40 hours to completely etch away the Al layer. After etching, the supernatant is neutral by centrifugal washing with ultrapure water for 6 to 8 times.
After the last washing, the product was dissolved again in 50mL of ultra-pure water and was subjected to ice water sonication for 3 hours under argon protection for delamination. Centrifuging at 3500rpm for 1 hr after ultrasonic treatment, collecting upper dark green suspension, and lyophilizing overnight to obtain single-layer Ti 3 C 2 T x And (3) a sample.
0.25g of single-layer Ti is weighed 3 C 2 T x And 0.412g sodium fluoroborate was added to 45mL of 0.8mol/L HCl and kept stirring for 30 minutes. Thereafter, the above solution was transferred to a polytetrafluoroethylene container and heated at 140℃for 16 hours. After the system is cooled to room temperature, washing the sample, centrifuging and drying at 60 ℃ overnight to obtain evenly dispersed powder Ti 3 C 2 T x /(001)TiO 2 。
The resulting powder was heated to 400℃in a muffle furnace at a rate of 5℃per minute and maintained for 1.5 hours to effect Ti 3 C 2 T x Controllable oxidation of surface groups to obtain Ti 3 C 2 O/(001)TiO 2 。
The invention is described in further detail below with reference to the attached drawing figures:
see the figure
FIG. 1 is an SEM image of an oxygen-terminated single-layer titanium carbide composite titania photocatalyst prepared in example 1. Wherein, single layer Ti 3 C 2 T x Clearly visible, indicating that ultrasound-assisted delamination is achieved. (001) The regular cubes of the planes are regular in shape and clear in edges, indicating TiO 2 Ideal synthesis and exposure of the highly active (001) side of (c). At the same time, (001) TiO can be clearly found 2 Attached to or embedded in a single layer of Ti 3 C 2 T x Surface, demonstrating a tight connection between the two materials.
FIG. 2 is a TEM image of an oxygen-terminated single-layer titanium carbide composite titania photocatalyst prepared in example 1. Wherein, tiO 2 The (001) crystal plane of (d) is clearly visible. Meanwhile, it is apparent from FIGS. 2a and b that Ti 3 C 2 O and (001) TiO 2 Is connected to the heterojunction of the first metal layer. It can be seen that (001) TiO 2 Mainly grow on Ti 3 C 2 T x Is equal to Ti 3 C 2 T x The structure is in close contact. Due to Ti 3 C 2 T x Such heterostructures are also known as schottky junctions, which facilitate the separation of electrons and holes by electron transitions during photoreaction. From the top view of FIG. 2c, it can be seen that (001) TiO 2 And single layer Ti 3 C 2 T x Is not uniform in size distribution. Blue framed (001) TiO 2 Size and white framed Ti 3 C 2 T x Is almost the same and shows an overlapping structure. At the same time, at Ti 3 C 2 T x Smaller (001) TiO can also be observed at the edges of (C) 2 And is embedded in its layered structure. It can be presumed that the Ti is obtained by ultrasonic separation 3 C 2 T x Is different in size. Specifically, part of Ti 3 C 2 T x After peeling, it separates into very small pieces, while the other part only achieves a preliminary peeling, resulting in (001) TiO 2 Is relatively dispersed in size.
FIG. 3 is an XPS chart of an oxygen-terminated monolayer titanium carbide composite titania photocatalyst prepared in example 1. As can be seen from the broad spectrum (FIG. 3 a), due to the addition of the crystal control agent NaBF 4 ，Ti 3 C 2 T x The peak intensities of both Na 1s and F1 s of (C) are significantly enhanced. At the same time, tiO 2 Also the formation of (c) results in an increase of the strength of Ti 2p and O1 s. In FIG. 3b, ti 3 C 2 T x The C1s spectrum of (C) can be divided into 5 peaks at 281.6, 282.3, 284.6, 286.3 and 288.6eV, respectively, which are assigned to C-Ti, C-Ti-O (H), C-C, C-O and C-F. With single Ti 3 C 2 T x Is compared with the characteristic peak position of Ti 3 C 2 O/(001)TiO 2 Is shifted to higher binding energies, possibly due to the formation of heterojunction structure leading to electrons from Ti at high fermi levels 3 C 2 T x Transfer to TiO 2 And (3) upper part. Ti (Ti) 3 C 2 T x Electron density of (2) is reduced, binding energy becomes large, and TiO 2 The opposite trend is presented. For the Ti 2p spectrum shown in FIG. 3C, five peaks at 454.4, 456, 458.5, 460.6 and 461.9eV can be fitted, respectively due to C-Ti-O, C-Ti- (OH), ti-CF, ti 3 C 2 -OH-H 2 Ti in O and Ti-C, explaining Ti 3 C 2 T x The main connection mode is Ti-C. Ti (Ti) 3 C 2 O/(001)TiO 2 Two typical peaks appear at 458.9 and 464.6eV for the Ti 2p spectrum of (A), respectively, belonging to Ti 4+ 2p 3/2 And Ti is 4+ 2p 1/2 Indicating TiO 2 Is present. In addition, the decrease in other peak intensities due to Ti-C linkages also indicates a fraction of Ti 3 C 2 T x Has been oxidized to TiO 2 . In the O1s spectrum, ti 3 C 2 T x Is combined with TiO 2 The adsorbed oxygen (529.9 eV) on the surface, lattice oxygen (531.5 eV) in Ti-O-Ti and Ti-OH (533 eV) agree. After complex formation, the peak intensity at 536eV, which is predominantly attributed to surface hydroxyl groups (C-OH), increases significantly. The O1s spectra show an opposite trend in peak shift compared to the Ti 2p and C1s spectra. Ti (Ti) 3 C 2 O/(001)TiO 2 Shifts to lower binding energies, indicating that TiO is post-electron transfer 2 Is consistent with the conclusion previously drawn from the C1s spectrum.
FIG. 4 is pure Ti 3 AlC 2 m-Ti3C2Tx and Ti prepared in example 1 3 C 2 O/(001)TiO 2 N of (2) 2 The adsorption-desorption curves, corresponding to BET surface areas, are listed in the inserted table of fig. 4. Pure Ti 3 AlC 2 (MXene) is accordion-shaped, and the sheets are closely contacted with each other, so that almost no N exists 2 Adsorption and desorption behavior. In contrast, layered m-Ti3C2Tx and Ti 3 C 2 O/(001)TiO 2 The surface area is significantly increased and the exposed area is greater. This phenomenon indicates that the exposed area of the layered material is larger and TiO grows after hydrothermal oxidation 2 Does not cause a stacked structure, and has larger contact area with water and light, which is highThe highly activated photolytic water is necessary for hydrogen production performance.
FIG. 5 is a graph showing the diffuse reflection of ultraviolet and visible light of the oxygen-terminated single-layer titanium carbide composite titanium dioxide photocatalyst prepared in example 1. Pure Ti 3 AlC 2 The absorption intensity of the material in the ultraviolet and visible wavelength ranges is relatively low, indicating that the unmodified material has poor photo-responsiveness. Ti (Ti) 3 C 2 O/(001)TiO 2 Exhibits significantly improved light absorption intensity, exhibits the most stable and excellent light absorption capacity in the spectral range from ultraviolet to visible light, which means Ti 3 C 2 O and (001) TiO 2 The heterostructure formed therebetween may promote light absorption to obtain good photocatalytic performance. Based on the Kubelka-Munk equation: (ahv) 1/2 =a (hv-Eg), bandgap energy (Eg) and (ahv) of the above sample 1/2 The graph calculation for hv is shown in fig. 5b as follows. Ti (Ti) 3 C 2 T x Is greater than the original Ti in terms of Eg value (1.17 eV) 3 AlC 2 A larger Eg value indicates that more light is required to excite, which is not ideal. In contrast, in the case of (001) TiO 2 After compounding, ti 3 C 2 O/(001)TiO 2 The Eg value of (2) was significantly reduced (0.75 eV).
FIG. 6 is a graph showing the comparative hydrogen production performance of the oxygen-terminated single-layer titanium carbide composite titania photocatalyst prepared in example 1. Ti (Ti) 3 C 2 T x /TiO 2 Is TiO-free 2 Crystal plane adjustment and high temperature annealing. Ti (Ti) 3 C 2 O/(001)TiO 2 、Ti 3 C 2 T x /TiO 2 And pure Ti 3 AlC 2 The photocatalytic water splitting hydrogen production experiment is performed in triethylamine water solution. During the whole irradiation, no pure Ti was detected 3 AlC 2 Generation of H 2 . At the same time Ti 3 C 2 T x /TiO 2 Shows lower activity, at a rate of only 11.4. Mu. Mol/(g.h), much lower than other materials reported so far. It can be inferred that the pure hydrothermal oxidation modification cannot effectively promote Ti 3 AlC 2 Is a photocatalytic effect of (a) in the reactor. This is probably due to the direct synthesis of TiO 2 Having a particle rather than a platelet-like morphology, the area of contact with light is largely limited, resulting in a limited number of photogenerated carriers. Most of the carriers are being transferred to Ti 3 C 2 T x The surface is self-assembled rapidly before, the effect of the Schottky structure is greatly inhibited, and thus the photocatalytic activity is reduced. After crystal face control and surface group adjustment, ti 3 C 2 O/(001)TiO 2 The photocatalytic water splitting hydrogen production activity is greatly enhanced. H 2 The precipitation rate increased to 149.99. Mu. Mol/(g.h) was Ti 3 C 2 T x /TiO 2 13.63 times, demonstrating the necessity of crystal plane control. At the same time Ti 3 C 2 The improvement of the content of the O functional groups on the surface also plays a role in improving the photocatalytic effect.
FIG. 7 is a graph showing the comparative photoelectrochemical properties of the oxygen-terminated single-layer titanium carbide composite titania photocatalyst prepared in example 1. Photoelectrochemical characterization was performed by Linear Sweep Voltammetry (LSV), mott-schottky curve, electrochemical Impedance Spectroscopy (EIS), and transient photocurrent response. LSV curve can pass through 10 mA.cm -2 And judging the PHE reaction degree by polarizing the overpotential corresponding to the current. As shown in FIG. 7a, ti 3 C 2 O/(001)TiO 2 And Ti is 3 C 2 T x The overpotential of (a) was 0.104 and 0.167mV, respectively. Clearly, ti is 3 C 2 O/(001)TiO 2 Reaching 10mA cm -2 The overpotential required for the current density is lower than other materials, indicating that the construction of the composite structure does help to improve the electrode performance, and Ti 3 C 2 T x As a conductive material is also the main driving force for improving HER performance. Ti (Ti) 3 C 2 T x And (001) TiO 2 The mott-schottky curves at both 500 and 1000Hz frequencies show positive slopes, indicating that both materials are typical n-type semiconductors. EIS and transient photocurrent response may further explain the formation of photoexcited carriers and the transfer behavior of electrons in the material. As shown in FIG. 7d, ti 3 C 2 O/(001)TiO 2 Is the smallest, probably due mainly to the TiO 2 Is introduced into (a)The construction of the interface heterojunction is promoted. Meanwhile, the single-layer structure exposes more active sites, and reduces material accumulation, so that an effective built-in electric field is formed, and charge transfer is accelerated. In addition, ti 3 C 2 O/(001)TiO 2 The highest transient photocurrent response intensity is also shown, which shows that the photo-generated carrier density is the largest, and the photocurrent response is obviously improved. Taken together with the above conclusion, ti 3 C 2 O/(001)TiO 2 The characteristics of fewer electron complexes and higher electron transfer efficiency are shown, and the photocatalytic reaction activity is improved.
The above is only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited by this, and any modification made on the basis of the technical scheme according to the technical idea of the present invention falls within the protection scope of the claims of the present invention.
Claims (5)
1. The application of the oxygen-terminated monolayer titanium carbide composite titanium dioxide photocatalyst in the photocatalytic hydrogen production is characterized in that firstly, a monolayer Ti is prepared by an in-situ hydrothermal oxidation method 3 C 2 T x Edge-grown (001) face-exposed TiO 2 The method comprises the steps of carrying out a first treatment on the surface of the Then increase Ti through annealing treatment 3 C 2 T x Content of surface oxygen groups; obtaining Ti 3 C 2 O/(001)TiO 2 Namely the oxygen end-capped monolayer titanium carbide composite titanium dioxide photocatalyst;
to single layer Ti 3 C 2 T x And NaBF 4 After being added into dilute HCl for dissolution, the in-situ hydrothermal oxidation reaction is carried out to realize the single-layer Ti 3 C 2 T x Edge-grown (001) face-exposed TiO 2 The method comprises the steps of carrying out a first treatment on the surface of the After the reaction is finished, cooling the system to room temperature, and collecting a product; washing, centrifuging and drying the obtained product to obtain uniformly dispersed powder;
annealing the obtained powder by heating to obtain Ti 3 C 2 T x Controllable oxidation of surface groups;
wherein the concentration of the dilute HCl is 0.5-2 mol/L;
the temperature of the in-situ hydrothermal oxidation reaction is 120-200 ℃, and the reaction time is 8-20 hours;
the annealing treatment temperature is 250-450 ℃, and the annealing time is 0.5-2 hours;
single layer Ti 3 C 2 T x The method comprises the following steps:
uniformly mixing LiF and concentrated HCl to obtain etching solution; ti is mixed with 3 AlC 2 Removing the Al layer in the etching solution by chemical etching, and washing to neutrality after etching to obtain multi-layer Ti 3 C 2 T x ；
The obtained multi-layer Ti 3 C 2 T x Dissolving in water, and carrying out ultrasonic treatment in an inert atmosphere for layering to obtain a dispersion system; centrifuging the obtained dispersion, collecting upper suspension, and lyophilizing the upper suspension to obtain single-layer Ti 3 C 2 T x ；
Wherein the concentration of the concentrated HCl is 9-12 mol/L.
2. The use of an oxygen-terminated monolayer titanium carbide composite titanium dioxide photocatalyst in photocatalytic hydrogen production according to claim 1, characterized in that the monolayer Ti 3 C 2 T x 、NaBF 4 The reaction feed ratio of the dilute HCl is (0.1-0.3) g: (0.165-0.495) g: (40-60) mL.
3. The use of an oxygen-terminated monolayer titanium carbide composite titanium dioxide photocatalyst in photocatalytic hydrogen production according to claim 1, characterized by LiF, concentrated HCl and Ti 3 AlC 2 The reaction feeding ratio of (1-3) g: (40-70) mL: (1-3) g.
4. The use of an oxygen-terminated monolayer titanium carbide composite titania photocatalyst in photocatalytic hydrogen production according to claim 1, wherein the operating parameters of the chemical etching include:
under the stirring condition, the etching temperature is 30-40 ℃ and the etching time is 24-48 hours.
5. The application of the oxygen-terminated monolayer titanium carbide composite titanium dioxide photocatalyst in photocatalytic hydrogen production according to claim 1, wherein the obtained multilayer Ti 3 C 2 T x After dissolving in water, carrying out ultrasonic treatment for 1.5-3 hours in an inert atmosphere to carry out layering.
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| g-C3N4/Ti3C2Tx (MXenes) composite with oxidized surface groups for efficient photocatalytic hydrogen evolution;Yuliang Sun，et al.;《J. Mater. Chem. A》;第6卷;第9124-9131页 * |
| Hybrids of Two-Dimensional Ti3C2 and TiO2 Exposing {001} Facets toward Enhanced Photocatalytic Activity;ChaoPeng，etal.;《ACS Appl. Mater. Interfaces》;第8卷;第6051−6060页 * |
| 溶剂热氧化少层Ti3C2MXene制备二维TiO2/Ti3C2复合光催化剂;严康等;《无机化学学报》;第35卷(第7期);第1203-1211页 * |
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