A nanostructured and Fe-rich 2+ Titanium dioxide / tin-iron oxide heterojunction and preparation method thereof

Abstract

The application discloses a kind of nanostructure controllable and rich Fe 2+ Titanium dioxide / tin-iron oxide heterojunction at high temperature and preparation method thereof.Utilize spin coating method on conductive glass substrate spin coating ultra-thin titanium carbide (Ti3C2MXene), then with iron chloride as iron source, by hydrothermal method on substrate preparation is hydroxyl iron oxide, then by immersion method to its tin doping, finally high temperature calcination, obtain a kind of nanostructure controllable and rich Fe 2+ Titanium dioxide / tin-iron oxide heterojunction at high temperature, namely TiO2 / Sn-Fe2O 3‑x The application utilizes the reducing property of titanium carbide to reduce part of iron oxide to Fe 2+ , and simultaneously oxidize titanium carbide to TiO2.The prepared photoanode still maintains good nanorod morphology after high temperature calcination, significantly improves the photoelectrochemical performance of iron oxide.It can be applied to the fields of photoelectrocatalytic water splitting, pollutant degradation and construction of photoelectrochemical sensors, etc.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of energy, and particularly relates to a nano-structure controllable and Fe 2+ -rich titanium dioxide / tin-iron oxide heterojunction at high temperature and a preparation method thereof. BACKGROUND

[0002] Photoelectrochemical (PEC) water splitting to produce hydrogen is considered as a promising solar energy utilization technology, which can not only meet the growing energy demand of human beings, but also has less impact on the environment. The key to the industrialization of PEC water splitting to produce hydrogen is to develop a cheap, efficient and stable photoelectrode. Among the developed photoelectrode materials, hematite (α-Fe2O3) is one of the most promising photoanode materials because of its good visible light absorption optical band gap (1.9-2.1 eV), high physical and chemical stability, environmental friendliness and low cost. However, the PEC water splitting performance of unmodified α-Fe2O3 photoanode is very low due to its improper band edge position, low electrical conductivity, short hole diffusion length (2-4 nm) and poor oxygen evolution reaction kinetics. Therefore, the comprehensive use of various synthesis process means to improve the PEC water splitting performance of α-Fe2O3 is the key to the industrialization of α-Fe2O3 photoanode.

[0003] Preparation of nano-structured α-Fe2O3 photoanode is one of the effective methods to improve its PEC water splitting performance, which not only can rapidly increase its light absorption area, but also can overcome the shortcoming of short photo-generated hole diffusion length due to nano-size effect, thereby improving its photon capture ability and photo-generated charge separation efficiency. However, the nano-structure prepared by nano-structured α-Fe2O3 is very easy to be destroyed by aggregation at high temperature. Doping of low-valence metal ions into α-Fe2O3 is another effective method to enhance its PEC water splitting performance. For example, the introduction of Fe 2+ can increase the donor density of α-Fe2O3 photoanode and improve its charge transfer efficiency. However, the introduction of low-valence metal ions, such as Fe 2+ , usually requires low temperature and oxygen-deficient reaction conditions, because Fe 2+ is easily oxidized to Fe 3+It can be seen that the preparation of nanostructured alpha-Fe2O3 or the introduction of low-valence metal ions into alpha-Fe2O3 tends to lower synthesis temperature conditions. However, low temperature conditions limit the possibility of further modification of alpha-Fe2O3, for example, improving its crystallinity or building a heterojunction, which all need high-temperature calcination. Building a heterojunction is widely considered as one of the most common and effective methods to improve the performance of PEC water splitting of photoelectrodes. In the case of alpha-Fe2O3, the heterojunction can change its band edge position, form an internal electric field, and thus improve its oxygen evolution reaction kinetics. TiO2 is often used to build a heterojunction with alpha-Fe2O3, and in order to enhance the contact between the two phases of alpha-Fe2O3 and TiO2, the calcination temperature often needs to be increased. However, as mentioned earlier, increasing the calcination temperature is not conducive to the structural stability of nano alpha-Fe2O3 and the introduction of low-valence metal ions. Therefore, developing a new method for preparing alpha-Fe2O3 heterojunction photoanodes that can not only maintain the stability of nano alpha-Fe2O3 at high temperatures but also introduce low-valence metal ions at the same time, has important theoretical guiding significance and practical value for the development of new synthesis processes of alpha-Fe2O3 photoanodes, the improvement of PEC water splitting performance, and the final industrialization.

[0004] MXenes material is a family of two-dimensional transition metal carbide, nitride or carbonitride, especially titanium carbide (Ti3C2 MXene), which has become a frontier hot material in the field of energy storage and conversion in recent years. Ti3C2 MXene can provide Ti source and nucleation site for the formation of TiO2 without external addition. In addition, thin-layer Ti3C2 MXene is a single-layer nanosheet, and due to its own rich surface defects and high reduction capacity, it is an excellent TiO2 precursor material. Therefore, Ti3C2 MXene can be used as a precursor of TiO2 and a carrier of other oxides to form a closely contacted atomic-level interface heterojunction.

[0005] In summary, the present application uses Ti3C2 MXene as a TiO2 precursor and develops a kind of titanium dioxide / tin-iron oxide heterojunction rich in Fe 2+ at high temperature and with controllable nanostructure, and a preparation method thereof, which has important scientific significance and application value for the development of high-performance alpha-Fe2O3 photoanodes in the future. SUMMARY

[0006] The present application aims to provide a kind of titanium dioxide / tin-iron oxide heterojunction rich in Fe 2+ at high temperature and with controllable nanostructure, and a preparation method thereof, which has the advantages of low cost and simple preparation process, and the obtained titanium dioxide / tin-iron oxide heterojunction photoanode has good photoelectrochemical (PEC) water splitting performance.

[0007] The technical solutions of the present invention are as follows:

[0008] A nanostructure-controllable and Fe-rich 2+ The titanium dioxide / tin-iron oxide heterojunction and its preparation method are characterized in that fluorine-doped tin oxide (FTO) conductive glass is used as a substrate, ultrathin titanium carbide (Ti3C2 MXene) is spin-coated on the substrate by a spin coating method, and then FeCl3·6H2O is used as an iron source to prepare FeOOH on the above substrate by a hydrothermal method, and then Sn is impregnated on it by an impregnation method. 4+ Finally, a nanostructured and Fe-rich composite was prepared by a one-step calcination method at high temperature. 2+ Titanium dioxide / tin-iron oxide heterojunction photoanode, i.e. TiO2 / Sn-Fe2O 3-x , specifically including the following steps:

[0009] (1) Ultrasonic cleaning of FTO conductive glass with acetone, isopropyl alcohol, ethanol and deionized water in sequence;

[0010] (2) preparing an ultra-thin titanium carbide ethanol solution and uniformly dispersing it by ultrasonication;

[0011] (3) The FTO conductive glass cleaned in step (1) is placed on a spin coater, and the solution in step (2) is added dropwise onto the FTO, and the glass is spin-coated. The above spin-coating steps are repeated 3 to 6 times, and the glass is calcined in air for 30 minutes after the spin-coating is completed.

[0012] (4) Prepare 20 mL of an aqueous solution containing 0.075 M ferric chloride and 0.15 M urea and stir to mix thoroughly;

[0013] (5) placing the FTO conductive glass obtained in step (3) with the conductive surface facing downward in a polytetrafluoroethylene liner in a hydrothermal kettle, adding the solution obtained in step (4) to the polytetrafluoroethylene liner, and then hydrothermally reacting in an oven at 100° C.;

[0014] (6) After the hydrothermal reaction in step (5) is completed, the mixture is naturally cooled to room temperature, the FTO conductive glass is rinsed with ultrapure water, and then placed in a blast drying oven at 40-80°C and dried for 0.1-1h;

[0015] (7) Prepare 20 mL of 0.1 M tin tetrachloride ethanol solution;

[0016] (8) The FTO conductive glass obtained in step (6) was placed in a tin tetrachloride ethanol solution, immersed, and then dried in an oven at 60°C for 15 minutes;

[0017] (9) The FTO conductive glass obtained in step (8) is placed in a tube furnace, calcined in air, and naturally cooled to room temperature to obtain Fe-rich 2+Titanium dioxide / tin-iron oxide nanorod heterojunction photoanode, namely TiO2 / Sn-Fe2O 3-x .

[0018] Furthermore, the concentration of the ultrathin titanium carbide ethanol solution prepared in step (2) is 0.5 to 2 mg / mL;

[0019] Furthermore, in step (3), the amount of the ultrathin titanium carbide ethanol solution added is 30 to 60 μL, the spin coating speed is 600 to 2000 rpm, and the calcination temperature is 300 to 400° C.;

[0020] Furthermore, the hydrothermal reaction time in step (5) is 3 to 9 hours;

[0021] Furthermore, the immersion time in step (8) is 5 to 15 minutes;

[0022] Furthermore, in step (9), the calcination time of the FTO conductive glass is 5 to 15 minutes, and the calcination temperature is 700 to 900° C.;

[0023] The beneficial effects of the present invention are:

[0024] (1) The preparation method of the present invention has simple process and low cost.

[0025] (2) The present invention makes full use of the reducing property of Ti3C2 MXene itself to produce Fe-rich 2+ The titanium dioxide / tin-iron oxide heterojunction photoanode significantly improved the donor density and charge transfer efficiency of the photoanode.

[0026] (3) In the present invention, during the one-step calcination of Sn-FeOOH to form tin-iron oxide nanorods, the Ti3C2 MXene pre-spin-coated on the conductive glass substrate is simultaneously converted into TiO2. This process not only enables close contact between TiO2 and tin-iron oxide, reducing the interfacial charge transfer resistance of the heterojunction, but also effectively prevents the iron oxide nanorods from agglomerating at high temperatures.

[0027] (4) TiO2 / Sn-Fe2O prepared by the present invention 3-x The heterojunction photoanode exhibits high stability and water splitting performance in the PEC water splitting process, which has high scientific significance and application value for the future development of high-performance α-Fe2O3 photoanodes. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The scanning electron microscope image of the prepared α-Fe2O3 photoanode shows that the α-Fe2O3 exhibits a nanorod structure and grows vertically along the FTO substrate.

[0029] Figure 2 Sn-Fe2O 3-x Scanning electron microscope photo of the photoanode. It can be seen from the figure that Sn 4+ After doping, the α-Fe2O3 nanorods aggregate together to form clusters.

[0030] Figure 3 TiO2 / Sn-Fe2O 3-x Scanning electron microscope photo of the photoanode. It can be seen from the figure that TiO2 / Sn-Fe2O 3-x The photoanode can still maintain the nanorod structure at high temperature, and the TiO2 / Sn-Fe2O 3-x The diameter of the nanorods is even smaller than that of α-Fe2O3 nanorods.

[0031] Figure 4 For the prepared α-Fe2O3, Sn-Fe2O 3-x and TiO2 / Sn-Fe2O 3-x XPS Fe 2p spectrum of the photoanode. As can be seen from the figure, Sn 4+ After doping, Fe 2+ The obvious increase is due to Sn 4+ Can induce Fe 3+ Reduction to Fe 2+ ; After forming a heterojunction with TiO2, Fe 2+ The further increase is due to the high reducibility of Ti3C2 MXene, which converts Fe in α-Fe2O3 into 3+ Partially reduced to Fe 2+ .

[0032] Figure 5 For the optimized α-Fe2O3, Sn-Fe2O 3-x and TiO2 / Sn-Fe2O 3-x Photoelectrochemical water splitting performance test of the photoanode under simulated sunlight, i.e. linear sweep voltammetry curve. As can be seen from the figure, TiO2 / Sn-Fe2O 3-x The PEC water splitting performance of the photoanode is significantly better than that of α-Fe2O3 and Sn-Fe2O 3-x Photoanode. DETAILED DESCRIPTION

[0033] The technical solutions and implementation methods of the present invention are described below by way of examples, but the technical solutions and implementation methods of the present invention are not limited to the following examples.

[0034] Example 1

[0035] α-Fe2O3 and Sn-Fe2O 3-x Preparation of photoanode

[0036] (1) Ultrasonic cleaning of FTO conductive glass with acetone, isopropyl alcohol, ethanol and deionized water in sequence;

[0037] (2) Prepare 20 mL of an aqueous solution containing 0.075 M ferric chloride and 0.15 M urea and stir to mix thoroughly;

[0038] (3) placing the FTO conductive glass obtained in step (1) with the conductive surface facing downward in a polytetrafluoroethylene liner in a hydrothermal kettle, adding the solution obtained in step (2) to the polytetrafluoroethylene liner, and then hydrothermally reacting in an oven at 100° C. for 5 h;

[0039] (4) After the hydrothermal reaction in step (3) is completed, the mixture is naturally cooled to room temperature, the FTO conductive glass is rinsed with ultrapure water, and then dried in a 60°C forced air drying oven for 15 minutes;

[0040] (5) Prepare 20 mL of 0.1 M tin tetrachloride ethanol solution;

[0041] (6) The FTO conductive glass obtained in step (4) was placed in a tin tetrachloride ethanol solution, immersed for 10 minutes, and then dried in a 60°C oven for 15 minutes;

[0042] (7) The dried FTO conductive glass in step (6) was placed in a tube furnace, calcined at 800°C in air for 10 min, and naturally cooled to room temperature to obtain a tin-iron oxide photoanode, i.e., Sn-Fe2O 3-x ; The FTO in step (4) is directly calcined to obtain a hematite photoanode, namely α-Fe2O3.

[0043] Example 2

[0044] TiO2 / Sn-Fe2O 3-x Preparation of photoanode

[0045] (1) Ultrasonic cleaning of FTO conductive glass with acetone, isopropyl alcohol, ethanol and deionized water in sequence;

[0046] (2) Prepare an ultrathin titanium carbide ethanol solution (0.5 mg / mL) and disperse it evenly by ultrasonication;

[0047] (3) The FTO conductive glass cleaned in step (1) was placed on a spin coater, 50 μL of the solution in step (2) was dropped onto the FTO, and the glass was spin-coated at a speed of 2000 rpm. The above spin-coating steps were repeated 6 times. After the spin-coating, the glass was calcined in air at 350°C for 30 min.

[0048] (4) Prepare 20 mL of an aqueous solution containing 0.075 M ferric chloride and 0.15 M urea and stir to mix thoroughly;

[0049] (5) The FTO conductive glass obtained in step (3) was placed in a Teflon liner in a hydrothermal kettle with the conductive surface facing down, and the solution obtained in step (4) was added to the Teflon liner, and then hydrothermal reaction was carried out in an oven at 100°C for 5h;

[0050] (6) After the hydrothermal reaction in step (5) was completed, the FTO conductive glass was naturally cooled to room temperature, then washed with ultrapure water, and then placed in a 60°C air-drying oven for 15min;

[0051] (7) A 20mL 0.1M tin tetrachloride ethanol solution was prepared;

[0052] (8) The FTO conductive glass obtained in step (6) was placed in the tin tetrachloride ethanol solution and soaked for 10min, and then dried in a 60°C oven for 15min;

[0053] (9) The dried FTO conductive glass in step (8) was placed in a tube furnace and calcined at 800°C in air for 10min, and then naturally cooled to room temperature to obtain a TiO2 / Sn-Fe2O3 nanorod heterojunction photoanode rich in Fe 2+ 3-x .

[0054] Example 3

[0055] Preparation of a TiO2 / Sn-Fe2O3 3-x photoanode

[0056] (1) The FTO conductive glass was cleaned with acetone, isopropanol, ethanol and deionized water in sequence under ultrasonic cleaning;

[0057] (2) An ultrathin titanium carbide ethanol solution was prepared, 1mg / mL, and ultrasonically dispersed uniformly;

[0058] (3) The cleaned FTO conductive glass in step (1) was placed on a spin coater, 50μL of the solution in step (2) was dropped on the FTO, and spin coating was carried out at a speed of 2000rpm, and the above spin coating step was repeated 6 times, and then calcination was carried out in air at 350°C for 30min after spin coating;

[0059] (4) A 20mL aqueous solution containing 0.075M iron chloride and 0.15M urea was prepared and mixed uniformly under stirring;

[0060] (5) The FTO conductive glass obtained in step (3) was placed in a Teflon liner in a hydrothermal kettle with the conductive surface facing down, and the solution obtained in step (4) was added to the Teflon liner, and then hydrothermal reaction was carried out in an oven at 100°C for 5h;

[0061] ​(6) After the hydrothermal reaction in step (5) is completed, the mixture is naturally cooled to room temperature, the FTO conductive glass is rinsed with ultrapure water, and then dried in a 60°C forced air drying oven for 15 minutes;

[0062] (7) Prepare 20 mL of 0.1 M tin tetrachloride ethanol solution;

[0063] (8) The FTO conductive glass obtained in step (6) was placed in a tin tetrachloride ethanol solution, immersed for 10 minutes, and then dried in an oven at 60°C for 15 minutes;

[0064] (9) The dried FTO conductive glass in step (8) was placed in a tube furnace, calcined at 800°C in air for 10 min, and naturally cooled to room temperature to obtain Fe-rich 2+ Titanium dioxide / tin-iron oxide nanorod heterojunction photoanode, namely TiO2 / Sn-Fe2O 3-x .

[0065] Example 4

[0066] TiO2 / Sn-Fe2O 3-x Preparation of photoanode

[0067] (1) Ultrasonic cleaning of FTO conductive glass with acetone, isopropyl alcohol, ethanol and deionized water in sequence;

[0068] (2) Prepare an ultrathin titanium carbide ethanol solution (2 mg / mL) and disperse it evenly by ultrasonication;

[0069] (3) The FTO conductive glass cleaned in step (1) was placed on a spin coater, 50 μL of the solution in step (2) was dropped onto the FTO, and the glass was spin-coated at a speed of 2000 rpm. The above spin-coating steps were repeated 6 times. After the spin-coating, the glass was calcined in air at 350°C for 30 min.

[0070] (4) Prepare 20 mL of an aqueous solution containing 0.075 M ferric chloride and 0.15 M urea and stir to mix thoroughly;

[0071] (5) placing the conductive surface of the FTO conductive glass obtained in step (3) facing downward in a polytetrafluoroethylene liner in a hydrothermal reactor, adding the solution obtained in step (4) to the polytetrafluoroethylene liner, and then hydrothermally reacting in an oven at 100° C. for 5 h;

[0072] (6) After the hydrothermal reaction in step (5) is completed, the mixture is naturally cooled to room temperature, the FTO conductive glass is rinsed with ultrapure water, and then dried in a 60°C forced air drying oven for 15 minutes;

[0073] (7) Prepare 20 mL of 0.1 M tin tetrachloride ethanol solution;

[0074] (8) The FTO conductive glass obtained in step (6) is placed in a tin tetrachloride ethanol solution, immersed for 10 min, and then dried in a 60°C oven for 15 min;

[0075] (9) The dried FTO conductive glass in step (8) is placed in a tube furnace and calcined at 800°C in air for 10 min, and naturally cooled to room temperature to obtain a TiO2 / Sn-Fe2O 2+ heterojunction photoanode rich in Fe 3-x .

[0076] Example 5

[0077] Preparation of a TiO2 / Sn-Fe2O 3-x photoanode

[0078] (1) The FTO conductive glass is cleaned with acetone, isopropanol, ethanol and deionized water in sequence under ultrasonic cleaning;

[0079] (2) An ultrathin titanium carbide ethanol solution is prepared, 1 mg / mL, and ultrasonically dispersed uniformly;

[0080] (3) The cleaned FTO conductive glass in step (1) is placed on a spin coater, 50 μL of the solution in step (2) is dropped on the FTO, and spin coating is performed at a speed of 2000 rpm, and the above spin coating step is repeated 6 times. After spin coating, calcination is performed at 350°C in air for 30 min;

[0081] (4) A 20 mL aqueous solution containing 0.075 M ferric chloride and 0.15 M urea is prepared, and stirred and mixed uniformly;

[0082] (5) The FTO conductive glass obtained in step (3) is placed in a Teflon liner in a hydrothermal kettle with the conductive surface facing down, the solution obtained in step (4) is added to the Teflon liner, and then hydrothermal reaction is performed in a 100°C oven for 3 h;

[0083] (6) After the hydrothermal reaction in step (5) is completed, the FTO conductive glass is naturally cooled to room temperature, washed with ultrapure water, and then placed in a 60°C forced air drying oven for 15 min;

[0084] (7) A 20 mL 0.1M tin tetrachloride ethanol solution is prepared;

[0085] (8) The FTO conductive glass obtained in step (6) is placed in a tin tetrachloride ethanol solution, immersed for 10 min, and then dried in a 60°C oven for 15 min;

[0086] (9) The dried FTO conductive glass in step (8) is placed in a tube furnace and calcined at 800°C in air for 10 min, and naturally cooled to room temperature to obtain a titanium dioxide / tin-iron oxide nanorod heterojunction photoanode rich in Fe 2+ , i.e. TiO2 / Sn-Fe2O 3-x .

[0087] Example 6

[0088] TiO2 / Sn-Fe2O 3-x photoanode

[0089] (1) The FTO conductive glass is cleaned with acetone, isopropyl alcohol, ethanol and deionized water in sequence by ultrasonic cleaning;

[0090] (2) An ultrathin titanium carbide ethanol solution is prepared, 1 mg / mL, and ultrasonic dispersion is uniform;

[0091] (3) The cleaned FTO conductive glass in step (1) is placed on a spin coater, 50 μL of the solution in step (2) is dropped on the FTO, and spin coating is performed at a speed of 2000 revolutions per minute, and the above spin coating step is repeated 6 times, and after spin coating, calcination is performed at 350°C in air for 30 min;

[0092] (4) A 20 mL aqueous solution containing 0.075 M iron chloride and 0.15 M urea is prepared, and stirring and mixing are uniform;

[0093] (5) The FTO conductive glass obtained in step (3) is placed in a polytetrafluoroethylene liner in a hydrothermal kettle with the conductive surface facing down, the solution obtained in step (4) is added to the polytetrafluoroethylene liner, and then hydrothermal reaction is performed in a 100°C oven for 7 h;

[0094] (6) After the hydrothermal reaction in step (5) is completed, the FTO conductive glass is naturally cooled to room temperature, cleaned with ultrapure water, and then placed in a 60°C air drying oven for drying for 15 min;

[0095] (7) A 20 mL 0.1M tin tetrachloride ethanol solution is prepared;

[0096] (8) The FTO conductive glass obtained in step (6) is placed in a tin tetrachloride ethanol solution, immersed for 10 min, and then dried in a 60°C oven for 15 min;

[0097] (9) The dried FTO conductive glass in step (8) is placed in a tube furnace and calcined at 800°C in air for 10 min, and naturally cooled to room temperature to obtain a titanium dioxide / tin-iron oxide nanorod heterojunction photoanode rich in Fe 2+ , i.e. TiO2 / Sn-Fe2O 3-x .

[0098] Example 7

[0099] TiO2 / Sn-Fe2O 3-x Preparation of photoanode

[0100] (1) Ultrasonic cleaning of FTO conductive glass with acetone, isopropyl alcohol, ethanol and deionized water in sequence;

[0101] (2) Prepare an ultrathin titanium carbide ethanol solution (1 mg / mL) and disperse it evenly by ultrasonication;

[0102] (3) The FTO conductive glass cleaned in step (1) was placed on a spin coater, 50 μL of the solution in step (2) was dropped onto the FTO, and the glass was spin-coated at a speed of 2000 rpm. The above spin-coating steps were repeated 6 times. After the spin-coating, the glass was calcined in air at 350°C for 30 min.

[0103] (4) Prepare 20 mL of an aqueous solution containing 0.075 M ferric chloride and 0.15 M urea and stir to mix thoroughly;

[0104] (5) placing the conductive surface of the FTO conductive glass obtained in step (3) facing downward in a polytetrafluoroethylene liner in a hydrothermal reactor, adding the solution obtained in step (4) to the polytetrafluoroethylene liner, and then hydrothermally reacting in an oven at 100° C. for 5 h;

[0105] (6) After the hydrothermal reaction in step (5) is completed, the mixture is naturally cooled to room temperature, the FTO conductive glass is rinsed with ultrapure water, and then dried in a 60°C forced air drying oven for 15 minutes;

[0106] (7) Prepare 20 mL of 0.1 M tin tetrachloride ethanol solution;

[0107] (8) The FTO conductive glass obtained in step (6) was placed in a tin tetrachloride ethanol solution, immersed for 5 minutes, and then dried in an oven at 60°C for 15 minutes;

[0108] (9) The dried FTO conductive glass in step (8) was placed in a tube furnace, calcined at 800°C in air for 10 min, and naturally cooled to room temperature to obtain Fe-rich 2+ Titanium dioxide / tin-iron oxide nanorod heterojunction photoanode, namely TiO2 / Sn-Fe2O 3-x .

[0109] Example 8

[0110] TiO2 / Sn-Fe2O 3-x Preparation of photoanode

[0111] (1) Ultrasonic cleaning of FTO conductive glass with acetone, isopropyl alcohol, ethanol and deionized water in sequence;

[0112] (2) Prepare an ultrathin titanium carbide ethanol solution (1 mg / mL) and disperse it evenly by ultrasonication;

[0113] (3) The FTO conductive glass cleaned in step (1) was placed on a spin coater, 50 μL of the solution in step (2) was dropped onto the FTO, and the glass was spin-coated at a speed of 2000 rpm. The above spin-coating steps were repeated 6 times. After the spin-coating, the glass was calcined in air at 350°C for 30 min.

[0114] (4) Prepare 20 mL of an aqueous solution containing 0.075 M ferric chloride and 0.15 M urea and stir to mix thoroughly;

[0115] (5) placing the conductive surface of the FTO conductive glass obtained in step (3) facing downward in a polytetrafluoroethylene liner in a hydrothermal reactor, adding the solution obtained in step (4) to the polytetrafluoroethylene liner, and then hydrothermally reacting in an oven at 100° C. for 5 h;

[0116] (6) After the hydrothermal reaction in step (5) is completed, the mixture is naturally cooled to room temperature, the FTO conductive glass is rinsed with ultrapure water, and then dried in a 60°C forced air drying oven for 15 minutes;

[0117] (7) Prepare 20 mL of 0.1 M tin tetrachloride ethanol solution;

[0118] (8) The FTO conductive glass obtained in step (6) was placed in a tin tetrachloride ethanol solution, immersed for 15 minutes, and then dried in an oven at 60°C for 15 minutes;

[0119] (9) The dried FTO conductive glass in step (8) was placed in a tube furnace, calcined at 800°C in air for 10 min, and naturally cooled to room temperature to obtain Fe-rich 2+ Titanium dioxide / tin-iron oxide nanorod heterojunction photoanode, namely TiO2 / Sn-Fe2O 3-x .

[0120] Example 9

[0121] TiO2 / Sn-Fe2O 3-x Preparation of photoanode

[0122] (1) Ultrasonic cleaning of FTO conductive glass with acetone, isopropyl alcohol, ethanol and deionized water in sequence;

[0123] (2) Prepare an ultrathin titanium carbide ethanol solution (1 mg / mL) and disperse it evenly by ultrasonication;

[0124] (3) The FTO conductive glass cleaned in step (1) was placed on a spin coater, 50 μL of the solution in step (2) was dropped onto the FTO, and the glass was spin-coated at a speed of 2000 rpm. The above spin-coating steps were repeated 6 times. After the spin-coating, the glass was calcined in air at 350°C for 30 min.

[0125] (4) Prepare 20 mL of an aqueous solution containing 0.075 M ferric chloride and 0.15 M urea and stir to mix thoroughly;

[0126] (5) placing the conductive surface of the FTO conductive glass obtained in step (3) facing downward in a polytetrafluoroethylene liner in a hydrothermal reactor, adding the solution obtained in step (4) to the polytetrafluoroethylene liner, and then hydrothermally reacting in an oven at 100° C. for 5 h;

[0127] (6) After the hydrothermal reaction in step (5) is completed, the mixture is naturally cooled to room temperature, the FTO conductive glass is rinsed with ultrapure water, and then dried in a 60°C forced air drying oven for 15 minutes;

[0128] (7) Prepare 20 mL of 0.1 M tin tetrachloride ethanol solution;

[0129] (8) The FTO conductive glass obtained in step (6) was placed in a tin tetrachloride ethanol solution, immersed for 10 minutes, and then dried in an oven at 60°C for 15 minutes;

[0130] (9) The dried FTO conductive glass in step (8) was placed in a tube furnace, calcined at 700°C in air for 10 min, and naturally cooled to room temperature to obtain Fe-rich 2+ Titanium dioxide / tin-iron oxide nanorod heterojunction photoanode, namely TiO2 / Sn-Fe2O 3-x .

[0131] Example 10

[0132] TiO2 / Sn-Fe2O 3-x 、Sn-Fe2O 3-x Photoelectrochemical water splitting performance test of α-Fe2O3 photoanode

[0133] The TiO2 / Sn-Fe2O prepared in Example 3 3-x Heterojunction photoanode, α-Fe2O3 and Sn-Fe2O prepared in Example 1 3-x The photoanode was used as the working electrode, the silver / silver chloride electrode was used as the reference electrode, and the platinum electrode was used as the counter electrode to form a three-electrode system connected to the electrochemical workstation. 50 mL of 1 mol / L NaOH solution was added to the quartz electrolytic cell, and the linear scanning curve test method was used to measure the TiO2 / Sn-Fe2O 3-xThe photocurrent density of the heterojunction photoanode is 2.32 times that of the α-Fe2O3 photoanode and 2.3 times that of the Sn-Fe2O 3-x 1.50 times that of the photoanode (bias voltage is 1.23V vs. RHE). 2+ The titanium dioxide / tin-iron oxide heterojunction and its preparation method have good practical application value.

[0134] The above embodiments are not limitations of the present invention, and the present invention is not limited to the above embodiments. As long as the requirements of the present invention are met, they belong to the protection scope of the present invention.

Claims

1. A nanostructure controllable and Fe-rich material at high temperature 2+ The titanium dioxide / tin-iron oxide heterojunction is characterized in that The heterojunction is prepared by the following method: using fluorine-doped tin oxide FTO conductive glass as a substrate, ultrathin titanium carbide Ti3C2 MXene is spin-coated on the substrate by a spin coating method, and then FeCl3·6H2O is used as an iron source to prepare FeOOH on the above substrate by a hydrothermal method, and then Sn is subjected to the immersion method. 4+ Finally, a one-step calcination method was used at high temperature to prepare a nanostructured and Fe-rich 2+ Titanium dioxide / tin-iron oxide heterojunction photoanode, i.e. TiO2 / Sn-Fe2O 3-x , specifically including the following steps: (1) Ultrasonic cleaning of FTO conductive glass with acetone, isopropyl alcohol, ethanol and deionized water in sequence; (2) preparing an ultra-thin titanium carbide ethanol solution and uniformly dispersing it by ultrasonication; (3) The FTO conductive glass cleaned in step (1) is placed on a spin coater, and the solution in step (2) is added dropwise onto the FTO, and the glass is spin-coated. The above spin-coating steps are repeated 3 to 6 times, and the glass is calcined in air for 30 minutes after the spin-coating is completed. (4) Prepare 20 mL of an aqueous solution containing 0.075 M ferric chloride and 0.15 M urea and stir to mix thoroughly; (5) placing the FTO conductive glass obtained in step (3) with the conductive surface facing downward in a polytetrafluoroethylene liner in a hydrothermal kettle, adding the solution obtained in step (4) to the polytetrafluoroethylene liner, and then hydrothermally reacting in an oven at 100° C.; (6) After the hydrothermal reaction in step (5) is completed, the mixture is naturally cooled to room temperature, the FTO conductive glass is rinsed with ultrapure water, and then placed in a blast drying oven at 40-80°C and dried for 0.1-1h; (7) Prepare 20 mL of 0.1 M tin tetrachloride ethanol solution; (8) The FTO conductive glass obtained in step (6) was placed in a tin tetrachloride ethanol solution, immersed, and then dried in an oven at 60°C for 15 minutes; (9) The FTO conductive glass obtained in step (8) is placed in a tube furnace, calcined in air, and naturally cooled to room temperature to obtain Fe-rich 2+ Titanium dioxide / tin-iron oxide nanorod heterojunction photoanode, namely TiO2 / Sn-Fe2O 3-x ; The calcination time is 5 to 15 minutes, and the calcination temperature is 700 to 900°C.

2. The nanostructure controllable and Fe-rich at high temperature as claimed in claim 1 2+ A titanium dioxide / tin-iron oxide heterojunction, characterized in that The concentration of the ultra-thin titanium carbide ethanol solution prepared in step (2) is 0.5-2 mg / mL.

3. The nanostructure controllable and Fe-rich at high temperature as claimed in claim 1 2+ A titanium dioxide / tin-iron oxide heterojunction, characterized in that In step (3), the amount of ultrathin titanium carbide ethanol solution added is 30-60 μL, the spin coating speed is 600-2000 rpm, and the calcination temperature is 300-400° C.

4. The nanostructure controllable and Fe-rich at high temperature as claimed in claim 1 2+ A titanium dioxide / tin-iron oxide heterojunction, characterized in that The hydrothermal reaction time in step (5) is 3 to 9 hours.

5. The nanostructure controllable and Fe-rich at high temperature as claimed in claim 1 2+ A titanium dioxide / tin-iron oxide heterojunction, characterized in that The immersion time in step (8) is 5 to 15 minutes.

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