A two-dimensional MXene functionalized In x Ga 1-x N nanorods and preparation methods and applications thereof

Abstract

The present invention discloses a two-dimensional MXene functionalized In x Ga 1‑x N nanorods and their preparation methods and applications. x Ga 1‑x The N nanocolumn includes a substrate, a MXene layer on the substrate, and an In x Ga 1‑x N nanorods; wherein 0≤x≤1. The present invention uses two-dimensional MXene as a substrate and In x Ga 1‑x The functional layer between the N nanopillars not only broadens the choice of substrates and reduces costs, but also effectively reduces the interface impedance between the substrate and the nanopillars, which is conducive to enhancing the carrier transport performance and greatly improving the photoelectric performance of the nanopillars. At the same time, it avoids the disadvantage that the nanopillars are easily etched on the substrate and improves their photoelectric stability. x Ga 1‑x N nanorods have important application prospects in photoelectrolytic water splitting to produce hydrogen, photodetectors, and solar cells.

Description

Technical Field

[0001] The present invention relates to x Ga 1-x N nanopillars, energy and catalysis, especially a two-dimensional MXene functionalized In x Ga 1-x N nanocolumn and its preparation method and application. Background Art

[0002] Photoelectrochemical (PEC) water splitting to produce hydrogen can effectively convert and store solar energy into clean, renewable hydrogen energy, and is one of the most promising means to solve the current energy crisis.

[0003] In recent years, ternary compound semiconductors In x Ga 1-x N nanopillars have important application prospects in PEC water splitting, mainly due to the In x Ga 1-x The N band gap is adjustable from 0.68 eV to 3.4 eV, which can realize photoelectrolysis of water in a wide spectral range. x Ga 1-x N has large electron mobility and strong conductivity, which can effectively reduce the cost of photolysis of water; secondly, In x Ga 1-x N nanorods have a large specific surface area, which can enhance light absorption and provide more reactive sites. x Ga 1-x The growth of N nanocolumns is mainly based on sapphire and single crystal Si substrates. However, they often have high resistivity (sapphire 10 14 Ω·cm, doped Si ~10Ω·cm), high cost and other issues. In addition, for example, when single crystal Si is used as the substrate, the grown In x Ga 1-x SiN will be formed between the N nanorods and the Si substrate. x Insulating layer. This insulating layer will not only increase the carrier transport resistance; at the same time, when In x Ga 1-x The N nanocolumn electrode performs photoelectrolysis of water in the electrolyte, and the insulating layer is easily etched away, making In x Ga 1-xN nanopillars will suffer from severe photocorrosion, resulting in a significant decrease in photoelectric performance. At present, a metal layer with a large work function is mainly used to reduce the interface impedance. However, the metal layer often brings about surface states, causing carrier recombination [Ebaid M, Min JW, Zhao C, et al. Water splitting to hydrogen over epitaxially grown InGaN nanowires on a metallic titanium / silicon template: reduced interfacial transfer resistance and improved stability to hydrogen [J]. Journal of Materials Chemistry A, 2018, 6 (16): 6922-6930.]. Therefore, it is necessary to find a method that can reduce the substrate interface resistance and improve the InGaN nanowires. x Ga 1-x Stability of photoelectric performance of N nanorod photoelectrode to In x Ga 1-x The photoelectrolytic production of hydrogen from water using N nanocolumns is of great significance.

[0004] Since the discovery of MXene (Ti3C2) materials in 2011, MXene has been widely used in energy storage, conversion and other fields as a new type of transition metal carbide or nitride. n+1 X n T, (n=1, 2, 3, M is a transition metal element, X is a carbon or nitrogen element, and T is an active functional group such as -OH, -F, -O). This material is mainly obtained by acid etching the MAX phase of layered ceramic materials and has excellent electrochemical and chemical reactivity. At the same time, this material has a two-dimensional crystal structure and is rich in active functional groups on the surface. It is an excellent carrier for realizing new structures and high-performance nanocatalysts. Summary of the invention

[0005] The purpose of the present invention is to provide a MXene functionalized In x Ga 1-x N nanorods and their preparation methods and applications. Two-dimensional MXene effectively reduces the large impedance between the nanorods and the substrate surface, and can significantly increase In x Ga 1-x The photoelectric conversion efficiency of N nanorods is improved, and the stability of use is enhanced; in addition, the preparation method overcomes the single selectivity of the substrate, reduces costs, simplifies the process, reduces energy consumption, saves time and is efficient.

[0006] The purpose of the present invention is achieved through the following technical solutions.

[0007] A two-dimensional MXene functionalized In x Ga 1-x N nanorods, including a substrate, a MXene layer on the substrate, and an In x Ga 1-x N nanopillars; where 0≤x≤1.

[0008] Furthermore, the substrate is a Si or FTO substrate.

[0009] Furthermore, the MXene is one or two of two-dimensional transition metal carbides, nitrides or carbonitrides such as Ti3C2, V2C, Ta4C3, MoC3, Ti3CN, etc.

[0010] Furthermore, the thickness of the MXene layer on the substrate is 3nm~200nm.

[0011] Furthermore, the In grown on the MXene layer x Ga 1-x The N nanocolumns include one or more of GaN nanocolumns, InGaN nanocolumns, InN nanocolumns, InGaN / GaN core / shell structure nanocolumns, and InN / InGaN core / shell structure nanocolumns.

[0012] Furthermore, the In grown on the MXene layer x Ga 1-x The height of N nanocolumns is 50~2000 nm and the diameter is 15~500 nm.

[0013] The above-mentioned two-dimensional MXene functionalized In x Ga 1-x The preparation method of N nanocolumns comprises the following steps:

[0014] (1) Preparation of MXene layer on substrate: MXene film is deposited on the substrate by using the pull-up dipping method, spin coating method or spray coating method. After drying, it is placed in a molecular beam epitaxy (MBE) reaction chamber and annealed at 700-900 °C to obtain a clean surface to obtain substrate / MXene.

[0015] (2) In on MXene layer x Ga 1-x Growth of N nanorods: The molecular beam epitaxy growth process was used to control the temperature of the substrate / MXene obtained in step (2) to 450-980 ºC, the substrate / MXene rotation speed to 5-10 r / min, and the Ga beam equivalent pressure to 1.0×10 -8~1.5×10 -7 Torr, the equivalent pressure of In beam is 1.0×10 -8 ~5×10 -7 Torr, nitrogen flow rate is 1~5sccm, plasma source power is 200~400 W, growth time is 1~5h, and In is grown on the substrate / MXene layer obtained in step (2). x Ga 1-x N nanopillars.

[0016] Furthermore, in step (1), the substrate is surface treated before coating the MXene film, including first plasma treatment or acid-base solution etching, then ultrasonic cleaning with ultrapure water, and then drying with high-purity nitrogen; the plasma treatment time is 10 to 30 minutes; the acid-base solution is BOE solution or Piranha solution, and the etching time is 1 to 5 minutes.

[0017] Furthermore, the drying in step (1) is vacuum drying, the drying temperature is 50-65°C, and the drying time is 10-30 min; and the annealing time is 10-30 min.

[0018] The above-mentioned two-dimensional MXene functionalized In x Ga 1-x Application of N nanorods in photoelectrolysis of water to produce hydrogen, photodetectors, and solar cells.

[0019] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0020] (1) The present invention uses MXene as In x Ga 1-x The dielectric layer of N nanocolumns can expand the choice of substrates and avoid the problem of choosing the same substrate as In. x Ga 1-x The N lattice mismatch has a large conductivity and is inexpensive, resulting in poor quality of the grown nanocolumn crystals, which reduces the preparation cost.

[0021] (2) The present invention uses MXene as In x Ga 1-x The dielectric layer of N nanocolumns has greatly improved the quality of the grown nanocolumn crystals, with a large specific surface area, which greatly reduces the probability of non-radiative recombination of carriers, increases the light absorption range, and increases the interface reaction area of ​​semiconductor / electrolyte, thus making In x Ga 1-x The photoelectric conversion efficiency of N nanocolumns is greatly improved.

[0022] (3) The present invention uses MXene as In x Ga1-x The dielectric layer in which the N nanocolumns grow increases the conductivity of the photoelectrode and enhances the carrier transport mechanism.

[0023] (4) The present invention uses MXene as a substrate and In x Ga 1-x The electron transport layer between the N nanocolumns greatly reduces the impedance between the substrate and the nanocolumns, speeds up the electron transfer rate between the substrate and the nanocolumns, and thus greatly improves the In x Ga 1-x Photoelectric conversion efficiency of N nanorod photoelectrolysis of water.

[0024] (5) A two-dimensional MXene functionalized In x Ga 1-x N nanocolumns, due to the SiN x With the elimination of the insulating layer, the catalyst exhibits excellent chemical stability, which greatly improves the photoelectric stability.

[0025] (6) In x Ga 1-x By adjusting the In component, the band gap of N nanocolumns can be adjusted in the range of 0.67-3.4 eV, which can realize photoelectrolysis of water to produce hydrogen in the visible light spectrum and improve the utilization rate of sunlight.

[0026] (7) Two-dimensional MXene functionalized with In x Ga 1-x When N nanorods are used for photoelectrolysis of water to produce hydrogen, In x Ga 1-x The nanocolumn structure of the N nanocolumn reduces the migration distance of the photogenerated carriers to the semiconductor / electrolyte interface, reduces the recombination probability of the photogenerated carriers, and is more conducive to the photogenerated electrons and holes to participate in the hydrogen evolution and oxygen evolution reactions respectively.

[0027] (8) The present invention uses two-dimensional MXene as a functional layer between the nanocolumns and the Si substrate, which is beneficial to the transport of carriers in the system and is not only suitable for photoelectrocatalysis, but also for the fields of solar cells and photodetectors. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 In is the two-dimensional MXene functionalized In in Example 1 x Ga 1-x Schematic cross-section of an N nanorod.

[0029] Figure 2 In is the two-dimensional MXene functionalized In in Example 1 x Ga 1-x SEM top view of N nanorods.

[0030] Figure 3 In is the two-dimensional MXene functionalized In in Example 1 x Ga 1-x Photocurrent and voltage curve of N nanorod photoanode.

[0031] Figure 4 This is a graph of the photocurrent and voltage of the two-dimensional MXene-functionalized InGaN nanocolumn photoelectrode in Example 2. DETAILED DESCRIPTION

[0032] The present invention will be further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto.

[0033] Example 1

[0034] A two-dimensional MXene functionalized In x Ga 1-x The method for preparing N nanocolumns comprises the following steps:

[0035] (1) Substrate selection: Si substrate is used.

[0036] (2) Substrate surface treatment: The substrate in step (1) was etched with Piranha solution for 1 min. It was then ultrasonically cleaned with ultrapure water and dried with high-purity nitrogen.

[0037] (3) Preparation of MXene layer on substrate: The MXene (Ti3C2) solution was coated on the substrate in step (2) by spin coating, and then dried at 50 ºC in vacuum for 30 min. The film thickness was 3 nm. Finally, it was placed in a molecular beam epitaxy (MBE) reaction chamber and annealed at 700 ºC for 30 min to obtain a clean surface.

[0038] (4) In on MXene layer x Ga 1-x Growth of N nanorods: Molecular beam epitaxy was used, with the substrate temperature controlled at 880 ºC, the substrate rotation speed at 10 r / min, and the Ga beam equivalent pressure at 3.5×10 -8 Torr, the equivalent pressure of In beam is 9.0×10 -8 Torr, the nitrogen flow rate was 2.0 sccm, the plasma source power was 400 W, and the growth time was 3 h. InGaN nanocolumns were grown on the substrate / MXene layer in step (3). The height of the nanocolumns was 300 nm, the diameter was 75 nm, and the In / Ga ratio was 25 / 75.

[0039] like Figure 1As shown, a cross-sectional schematic diagram of a two-dimensional MXene-functionalized InGaN nanocolumn in this embodiment includes a Si substrate 1, a MXene layer 2 on the Si substrate 1, and an InGaN nanocolumn 3 grown on the MXene layer 2.

[0040] like Figure 2 As shown, a scanning electron microscope top view of a two-dimensional MXene-functionalized InGaN nanocolumn of this embodiment.

[0041] The InGaN nanorods functionalized with a two-dimensional MXene in this embodiment are used for photoelectrolysis of water to produce hydrogen: The InGaN nanorods prepared in this embodiment are made into photoelectrodes, and the specific steps are as follows: a metal layer is deposited by electron beam evaporation to form an ohmic contact with the back of Si, and then a metal wire is used to connect the metal layer, and the entire metal back is protected with an insulating epoxy resin. Finally, an electrochemical workstation is used for photoelectrochemical testing, as follows: a 0.5 mol / L H2SO4 solution is used as the electrolyte, the prepared photoelectrode is used as the anode, a saturated calomel electrode (SCE) is used as the reference electrode, a Pt wire is used as the cathode, and a 300 W Xe lamp (light intensity ~100 mW / cm 2 ) as the light source, and the photocurrent density-bias curve was obtained. The photoelectrode based on InGaN nanocolumns on two-dimensional MXene prepared by this process has a photocurrent density of 1 mA / cm at 1.0 V vs. SCE bias. 2 , the bias photoelectric conversion efficiency (ABPE) is 1.2%.

[0042] like Figure 3 As shown, a photocurrent and voltage curve of a two-dimensional MXene-functionalized InGaN nanocolumn photoelectrode in this embodiment.

[0043] Example 2

[0044] A method for preparing two-dimensional MXene-functionalized GaN nanocolumns comprises the following steps:

[0045] (1) Substrate selection: Si substrate is used.

[0046] (2) Substrate surface treatment: The substrate in step (1) was etched with Piranha solution for 5 min. It was then ultrasonically cleaned with ultrapure water and dried with high-purity nitrogen.

[0047] (3) Preparation of MXene layer on substrate: Spin coating was used to coat the MXene (Ti3C2) solution on the substrate in step (2), and then dried at 65°C in vacuum for 30 minutes to a film thickness of 80 nm. Finally, the film was placed in a molecular beam epitaxy (MBE) reaction chamber and annealed at 800°C for 20 minutes to obtain a clean surface.

[0048] (4) Growth of GaN nanocolumns on the MXene layer: Molecular beam epitaxy was used to grow GaN nanocolumns. The substrate temperature was controlled at 980 °C, the substrate rotation speed was 5 r / min, and the Ga beam equivalent pressure was 1.5×10 -7 Torr, the equivalent pressure of In beam is 1.0×10 -8 Torr, the nitrogen flow rate was 1.0 sccm, the plasma source power was 200 W, and the growth time was 5 h. In step (3), GaN nanocolumns were grown on the substrate / MXene layer. The height of the nanocolumns was 150 nm and the diameter was 50 nm.

[0049] A two-dimensional MXene-functionalized GaN nanorod in this embodiment is used for photoelectrolysis of water to produce hydrogen: The GaN nanorod prepared in this embodiment is made into a photoelectrode, and the specific steps are as follows: a metal layer is deposited by electron beam evaporation to form an ohmic contact with the back of Si, and then a metal wire is used to connect the metal layer, and the entire metal back is protected with an insulating epoxy resin. Finally, an electrochemical workstation is used for photoelectrochemical testing, as follows: a 0.5 mol / L H2SO4 solution is used as the electrolyte, the prepared photoelectrode is used as the anode, a saturated calomel electrode (SCE) is used as the reference electrode, a Pt wire is used as the cathode, and a 300 W Xe lamp (light intensity ~100 mW / cm 2 ) as the light source, and the photocurrent density-bias curve was obtained. The photoelectrode based on GaN nanopillars on two-dimensional MXene prepared by this process has a photocurrent density of 2.9 mA / cm at 1.0 V vs. SCE bias. 2 , the bias photoelectric conversion efficiency (ABPE) is 0.8%.

[0050] like Figure 4 Shown is a photocurrent and voltage curve of a two-dimensional MXene-functionalized InGaN nanocolumn photoelectrode of this embodiment.

[0051] Example 3

[0052] A method for preparing two-dimensional MXene-functionalized InN nanocolumns comprises the following steps:

[0053] (1) Substrate selection: Si is used.

[0054] (2) Substrate surface treatment: The substrate in step (1) was etched with Piranha solution for 2 min. It was then ultrasonically cleaned with ultrapure water and dried with high-purity nitrogen.

[0055] (3) Preparation of MXene layer on substrate: The MXene (Ti3C2) solution was coated on the substrate in step (2) by spin coating, and then dried at 65 ºC in vacuum for 10 min. The film thickness was 120 nm. Finally, it was placed in a molecular beam epitaxy (MBE) reaction chamber and annealed at 900 ºC for 10 min to obtain a clean surface. The height of the nanopillars was 1200 nm and the diameter was 80 nm.

[0056] (4) Growth of InN nanocolumns on the MXene layer: Molecular beam epitaxy was used with a substrate temperature of 450 °C, a substrate rotation speed of 10 r / min, and a Ga beam equivalent pressure of 1.0 × 10 -8 Torr, the equivalent pressure of In beam is 5.0×10 -7 Torr, nitrogen flow rate was 5.0 sccm, plasma source power was 400 W, growth time was 1 h, and InN nanorods were grown on the substrate / MXene layer in step (3).

[0057] Example 4

[0058] A method for preparing a two-dimensional MXene-functionalized GN nanocolumn comprises the following steps:

[0059] (1) Substrate selection: FTO substrate is used.

[0060] (2) Substrate surface treatment: The substrate in step (1) was etched with Piranha solution for 2 min. It was then ultrasonically cleaned with ultrapure water and dried with high-purity nitrogen.

[0061] (3) Preparation of MXene layer on substrate: Spin coating was used to coat the MXene (Ti3C2) solution on the substrate in step (2), and then dried at 65°C in vacuum for 30 minutes to a film thickness of 80 nm. Finally, the film was placed in a molecular beam epitaxy (MBE) reaction chamber and annealed at 800°C for 20 minutes to obtain a clean surface.

[0062] (4) Growth of GaN nanocolumns on the MXene layer: Molecular beam epitaxy was used to grow the GaN nanocolumns. The substrate temperature was controlled at 980 °C, the substrate rotation speed was 5 r / min, and the Ga beam equivalent pressure was 1.5×10 -7 Torr, the equivalent pressure of In beam is 1.0×10 -8 Torr, the nitrogen flow rate was 1.0 sccm, the plasma source power was 200 W, and the growth time was 5 h. In step (3), GaN nanocolumns were grown on the substrate / MXene layer. The height of the nanocolumns was 250 nm and the diameter was 65 nm.

[0063] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A 2D MXene functionalized In x Ga 1-x N nanopillars, characterized in that The invention comprises a substrate (1), a MXene layer (2) on the substrate (1), and an Indium layer grown on the MXene layer (2). x Ga 1-x N nanopillars (3); wherein 0≤x≤1; the MXene is one or two of Ti3C2, V2C, Ta4C3, MoC3, and Ti3CN; The thickness of the MXene layer on the substrate is 3nm~200nm; The In grown on the MXene layer x Ga 1-x The N nanocolumns include one or more of GaN nanocolumns, InGaN nanocolumns, InN nanocolumns, InGaN / GaN core / shell structure nanocolumns, and InN / InGaN core / shell structure nanocolumns; The In grown on the MXene layer x Ga 1-x The height of N nanocolumns is 50~2000 nm and the diameter is 15~500 nm.

2. A two-dimensional MXene functionalized In according to claim 1 x Ga 1-x N nanopillars, characterized in that The substrate is a Si substrate or a FTO substrate.

3. Preparation of a two-dimensional MXene functionalized In according to any one of claims 1-2 x Ga 1-x N nanopillars method, characterized in that The following steps are involved: (1) Preparation of MXene layer on substrate: MXene film is deposited on the substrate by using the Czochralski method, spin coating method or spray coating method. After drying, the MXene film is placed in a molecular beam epitaxy reaction chamber and annealed at 700-900 °C to obtain substrate / MXene. (2) In on MXene layer x Ga 1-x Growth of N nanorods: The molecular beam epitaxy growth process was used to control the temperature of the substrate / MXene obtained in step (1) to 450-980 ºC, the substrate / MXene rotation speed to 5-10 r / min, and the Ga beam equivalent pressure to 1.0×10 -8 ~1.5×10 -7 Torr, the equivalent pressure of In beam is 1.0×10 -8 ~5×10 -7 Torr, nitrogen flow rate is 1~5sccm, plasma source power is 200~400 W, growth time is 1~5h, and In is grown on the Mxene layer of the substrate / Mxene obtained in step (1). x Ga 1-x N nanopillars.

4. The method according to claim 3, characterized in that: In step (1), the substrate is surface treated before coating the MXene film, including first plasma treatment or acid-base solution etching, then ultrasonic cleaning with ultrapure water, and then drying with high-purity nitrogen; the plasma treatment time is 10 to 30 minutes; the acid-base solution is BOE solution or Piranha solution, and the etching time is 1 to 5 minutes.

5. The method according to claim 3, characterized in that: The drying in step (1) is vacuum drying, the drying temperature is 50-65°C, and the drying time is 10-30 minutes; the annealing time is 10-30 minutes.

6. A two-dimensional MXene functionalized In according to any one of claims 1-2 x Ga 1-x Application of N nanorods in photoelectrolysis of water to produce hydrogen, photodetectors or solar cells.

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