CN107541724A - A kind of preparation method of the controllable metal-oxide film of pattern and composition - Google Patents

Abstract

The invention relates to the field of photoelectrochemical cells, in particular to a method for preparing a metal oxide thin film with controllable morphology and composition. Using a metal sheet or an alloy sheet as a substrate, the amorphous metal oxide is generated in situ on the surface of the metal sheet or alloy substrate by chemical corrosion oxidation; the obtained amorphous metal oxide film is subjected to crystallization heat treatment under different oxygen partial pressures, A metal oxide thin film with controllable morphology and composition is obtained by adjusting the heat treatment temperature and time. In the present invention, by adjusting the oxygen partial pressure in the crystallization heat treatment process, a method for obtaining a metal oxide film with a specific shape and an adjustable composition on a metal substrate in situ, the shape and composition of the metal oxide film are photochemical water splitting cells Two important parameters of photoelectrode materials directly affect the final conversion efficiency of photoelectrochemical cells. In the invention, the metal oxide thin film with specific shape and adjustable composition is obtained in situ on the metal substrate by regulating the atmosphere and partial pressure in the heat treatment process.

Description

A method for preparing metal oxide thin films with controllable morphology and composition

technical field

The invention relates to the field of photoelectrochemical cells, in particular to a method for preparing a metal oxide thin film with controllable morphology and composition.

Background technique

Photoelectrochemical water splitting cells are one of the effective ways to convert and store solar energy, which fix and convert solar energy in the form of hydrogen bonds. Photoelectrodes are the core components of photoelectrochemical cells, which absorb incident solar light and induce water splitting reactions to convert and store solar energy. Metal oxides have the advantages of high stability, high activity and low cost, and are ideal semiconductor photoelectrode materials.

The surface atomic/electronic structure of metal oxides directly determines the surface transfer process of photogenerated charges, which ultimately affects the quantum conversion efficiency of photoelectrodes. Different crystal planes of metal oxide semiconductors have different surface atomic/electronic structures, which exhibit different photocatalytic activities, and usually high-energy crystal planes have higher photocatalytic activity. At the same time, surface lattice defects can also simultaneously modulate the surface atomic/electronic structure, directly affecting the final quantum conversion efficiency. By modulating the surface atomic/electronic structure, obtaining a metal oxide film with specific crystal plane exposure and composition adjustment can effectively improve the surface transfer efficiency of photogenerated charges, and it has high quantum efficiency of solar energy conversion as a photoelectrode. Therefore, the preparation of metal oxide thin film photoelectrodes with specific crystal facet exposure and tunable composition is an effective means to construct high-efficiency photoelectrochemical water splitting batteries.

Contents of the invention

The object of the present invention is to provide a method for preparing a metal oxide thin film with controllable morphology and composition. By adjusting the atmosphere and partial pressure during heat treatment, a specific morphology and composition-tunable metal oxide film can be obtained in situ on a metal substrate. object film.

Technical scheme of the present invention is:

A method for preparing a metal oxide thin film with controllable morphology and composition. First, using a metal sheet or an alloy sheet as a substrate, using chemical corrosion and oxidation to generate an amorphous metal oxide in situ on the surface of the metal sheet or alloy substrate; and then The obtained amorphous metal oxide film is subjected to crystallization heat treatment under different oxygen partial pressures, and the metal oxide film with controllable morphology and composition is obtained by adjusting the heat treatment temperature and time.

The metal substrate is Fe, Ta, Ti, W, Zn, Cu or Co, and the alloy substrate is Ti/Al, Cu/Zn, Ti/Fe, Ti/W or Ti/Ta alloy.

The chemical corrosion oxidation refers to various metal corrosion oxidation processes, using chemical solution corrosion, atmospheric corrosion or electrochemical oxidation corrosion.

The crystallization heat treatment temperature is 300-1000° C., the heating rate is 0.1-10° C./minute, and the crystallization time is 0.5-48 hours.

In the preparation method of the metal oxide thin film with controllable morphology and composition, preferably, the crystallization heat treatment temperature is 500-800°C, the heating rate is 1-5°C/min, and the crystallization time is 1-5°C. 24 hours.

The partial pressure of oxygen in the crystallization treatment is 0-10 ⁵ Pa.

In the preparation method of the metal oxide thin film with controllable morphology and composition, preferably, the partial pressure of oxygen in the crystallization treatment is 0-1000Pa.

Design idea of the present invention is:

In the present invention, the metal (or alloy) sheet is used as the substrate, and the amorphous metal oxide film is obtained in situ on the metal (alloy) substrate through (electro)chemical corrosion oxidation, and the crystallization heat treatment atmosphere and partial pressure of the amorphous film are controlled. In-situ acquisition of specific morphology and composition-tunable metal oxide films on metal (alloy) substrates: Utilizing the differences in thermodynamically stable configurations of metal oxide crystals under different oxygen partial pressures, the obtained amorphous metal oxide films are obtained in different Crystallization heat treatment is carried out under oxygen partial pressure. By adjusting the heat treatment temperature and time, a metal oxide film with a specific crystal surface exposed can be obtained; the obtained amorphous metal oxide The film is crystallized in an anaerobic environment (such as under an argon atmosphere), and metal oxide films with different components can be obtained by adjusting the heat treatment temperature and time.

Advantage of the present invention and beneficial effect are:

1. The present invention utilizes (electro)chemical corrosion and oxidation method to in-situ oxidize and etch and grow the amorphous metal oxide film on the metal (alloy) substrate, which can easily realize the preparation of various amorphous metal oxide films.

2. By simply adjusting the oxygen partial pressure during the crystallization process of the amorphous metal oxide film, the present invention can obtain a metal (oxygen) nitride film with adjustable morphology and composition, and can effectively control its photoelectric catalytic water splitting activity.

Description of drawings

Figure 1. Schematic diagram (ab) of the preparation process of amorphous _TiO2 thin films and corresponding scanning electron microscope (SEM) photographs (cd).

Figure 2. SEM images of rutile TiO ₂ nanopillar single crystal arrays: (a) low magnification photo, (b) high magnification top photo and (c) high magnification side photo, the inset in (c) is the thermodynamically stable configuration of rutile TiO ₂ (Wulff configuration) schematic diagram.

Figure 3. Transmission electron microscope (TEM) photos of rutile TiO ₂ nanocolumns: (A) low-magnification photo of a single nanocolumn, (B) high-resolution TEM photo and (C) selected electron diffraction spots.

Figure 4. Photoelectrochemical water splitting activity test of rutile TiO ₂ nanopillar single crystal array photoelectrode and traditional anatase TiO ₂ nanotube photoelectrode: (a) Test curve of rutile TiO ₂ nanopillar single crystal array in dark state, ( b) Test curve of traditional anatase _TiO2 nanotubes in dark state, (c) test curve of rutile _TiO2 nanopillar single crystal array under light, (d) test curve of traditional anatase _TiO2 nanotubes under light. The X-axis is the applied voltage (V/V), and the Y-axis is the photocurrent density (mA·cm ^-2 ).

Fig. 5. X-ray photoelectron spectroscopy (XPS) elemental depth analysis (a) and schematic diagram of elemental depth distribution (bc) of stoichiometric and non-stoichiometric rutile _TiO2 thin films. The X-axis is the sputtering time (second/s), and the Y-axis is the O/Ti atomic ratio.

Figure 6. Photoelectrochemical water splitting activity test of stoichiometric rutile TiO ₂ thin film photoelectrode and non-stoichiometric rutile TiO ₂ thin film photoelectrode: (a) test curve of stoichiometric rutile TiO ₂ thin film in dark state, (b) Non-stoichiometric rutile TiO ₂ film, (c) test curve of stoichiometric rutile TiO ₂ film under light, (d) test curve of non-stoichiometric rutile TiO ₂ film under light. The X-axis is the applied voltage (V/V), and the Y-axis is the photocurrent density (mA·cm ^-2 ).

detailed description

In the specific implementation process, the present invention uses (electro)chemical corrosion oxidation to grow amorphous metal oxide films in situ on metal (alloy) substrates, and obtains specific morphology and composition by regulating the oxygen partial pressure in the crystallization process. controlled metal oxide thin films. Using a metal (alloy) sheet as a substrate, first obtain an amorphous metal oxide film on the metal (alloy) substrate in situ by (electro)chemical corrosion oxidation; using the difference in thermodynamically stable configuration of metal oxide crystals under different oxygen partial pressures As well as the reduction of the metal substrate to the metal oxide film at high temperature, the obtained amorphous metal oxide film is subjected to crystallization heat treatment under different oxygen partial pressures, and the specific morphology and composition can be obtained by adjusting the heat treatment temperature and time. The metal oxide thin film, specifically as follows:

1. The substrates are various metal and alloy substrates, including various pure metal sheets (such as: Fe, Ta, Ti, W, Zn, Cu, Co, etc.) and various alloy sheets (such as: Ti/ Al, Cu/Zn, Ti/Fe, Ti/W, Ti/Ta alloy, etc.).

2. The (electro)chemical corrosion oxidation refers to various metal corrosion oxidation processes, including chemical solution corrosion, atmospheric corrosion and electrochemical oxidation corrosion.

3. The crystallization heat treatment temperature is 300-1000° C., the heating rate is 0.1-10° C./minute, and the crystallization time is 0.5-48 hours.

4. The partial pressure of oxygen in the crystallization treatment ranges from 0 to 10 ⁵ Pa.

The present invention will be further described in detail below in conjunction with the embodiments and the accompanying drawings.

Example 1

Metal titanium (Ti) sheet (length 1cm × width 2.5cm) was ultrasonically cleaned in deionized water, ethanol, acetone, and isopropanol for 15 minutes respectively, and after drying, it was connected to the positive electrode of the power supply, and the Pt sheet was connected to the negative electrode. And inserted into the mixed solution of ethylene glycol and water (volume ratio 9:1) containing NH ₄ F (2-5 wt%). Apply a constant voltage of 60V for 6 hours, in-situ anodize the surface of the metal titanium sheet to form a TiO ₂ nanotube array, then take the titanium sheet out and put it into hydrogen peroxide water for ultrasonication, remove the TiO ₂ nanotube array on the surface to obtain a dense amorphous bottom _TiO2 thin film (Figure 1). The obtained amorphous dense film was crystallized under an oxygen atmosphere, the oxygen partial pressure was controlled at 1000Pa, the crystallization was carried out at 550°C for 2 hours, and the heating rate was 5°C/min to obtain a rutile TiO ₂ single crystal nanocolumn array with the top exposed High-energy (111) and (101) crystal planes (Figure 2). The as-prepared rutile _TiO2 single crystal nanocolumn arrays have excellent activity as photoanodes for photoelectrochemical water splitting cells due to the higher water oxidation activity of the high-energy crystal planes.

As shown in Figure 1, the TiO ₂ nanotube array (a) was obtained by electrochemically anodizing the Ti sheet, and the TiO ₂ nanotubes on the surface were further removed by ultrasonic peeling to obtain a dense amorphous TiO ₂ film (b).

As shown in Figure 2, after 2 hours of treatment at 550°C and 1000Pa oxygen partial pressure, from the low-magnification scanning electron microscope photos, the TiO ₂ crystal array in the domain region (a) can be observed; in the high-magnification top (b) and side (c) In the scanning electron microscope photo, it can be observed that it is a rutile TiO ₂ nanocolumn array structure exposed by a specific crystal plane. By comparing with the thermodynamically stable configuration (Wulff configuration), the top exposed crystal planes are (101) and ( 111) crystal plane, and the side is (110) crystal plane.

As shown in Figure 3, the low-magnification transmission electron microscope photo (A) of a single nanocolumn with complete crystal plane development, combined with the high-resolution transmission electron micrograph of the nanocolumn (B) and the selected area electron diffraction photo (C) prove that the single nanocolumn is single crystal structure.

As shown in Figure 4, in the dark state, both the rutile TiO ₂ single crystal nanopillar array (a) and the anatase TiO ₂ nanotube array (b) have no water splitting current response; Compared with the photocurrent of _TiO2 nanotube array (d), the rutile _TiO2 single crystal nanopillar array (c) exhibits superior photoelectrochemical water splitting performance.

Example 2

Metal titanium (Ti) sheet (length 1cm × width 2.5cm) was ultrasonically cleaned in deionized water, ethanol, acetone, and isopropanol for 15 minutes respectively, and after drying, it was connected to the positive electrode of the power supply, and the Pt sheet was connected to the negative electrode. And inserted into the mixed solution of ethylene glycol and water (volume ratio 9:1) containing NH ₄ F (2-5 wt%). Apply a constant voltage of 60V for 6 hours, in-situ anodize the surface of the metal titanium sheet to form a TiO ₂ nanotube array, then take the titanium sheet out and put it into hydrogen peroxide water for ultrasonication, remove the TiO ₂ nanotube array on the surface to obtain a dense amorphous bottom _TiO2 thin film (Figure 1). The obtained amorphous dense film was crystallized in an anaerobic atmosphere (Ar or N gas atmosphere), the oxygen partial pressure was 0 Pa, and kept at 550°C for 2 hours, and the reduction of _TiO2 by metal titanium at high temperature was used to obtain non-crystalline Stoichiometric rutile _TiO2 thin films. Compared with the stoichiometric rutile TiO ₂ film obtained by crystallization in air atmosphere (oxygen partial pressure level is 10 ⁴ Pa), the non-stoichiometric rutile TiO ₂ film has higher photoelectrochemical water splitting activity.

As shown in Figure 5, through the XPS element depth distribution analysis, the stoichiometric gold sweet potato TiO ₂ film obtained by heat treatment in the air, the O//Ti atomic ratio in the bulk phase of the film is close to 2; while heat treatment in anaerobic atmosphere The resulting non-stoichiometric rutile _TiO2 thin films. The O//Ti atomic ratio in the bulk phase of the film is less than 2.

As shown in Figure 6, in the dark state, both the non-stoichiometric rutile TiO ₂ film (a) and the stoichiometric rutile TiO ₂ film (b) have no water splitting current response; ₂ film (c), the non-stoichiometric rutile TiO ₂ film (d) exhibits superior photoelectrochemical water splitting performance.

The results of the examples show that the present invention obtains a specific morphology and composition-tunable metal oxide film on a metal (alloy) substrate in situ by regulating the oxygen partial pressure in the crystallization heat treatment process, and the shape of the metal oxide film Appearance and composition are two important parameters of photoelectrode materials for photochemical water splitting cells, which directly affect the final conversion efficiency of photoelectrochemical cells.

Claims (7)

1. A method for preparing a metal oxide film with controllable morphology and composition, characterized in that: first, using a metal sheet or an alloy sheet as a substrate, utilizing chemical corrosion oxidation to generate non- Crystalline metal oxide; then, the obtained amorphous metal oxide film is subjected to crystallization heat treatment under different oxygen partial pressures, and a metal oxide film with controllable morphology and composition is obtained by adjusting the heat treatment temperature and time. 2. According to the preparation method of the metal oxide thin film whose morphology and composition are controllable according to claim 1, it is characterized in that: the metal substrate is Fe, Ta, Ti, W, Zn, Cu or Co, and the The alloy substrate mentioned above is Ti/Al, Cu/Zn, Ti/Fe, Ti/W or Ti/Ta alloy. 3. According to the preparation method of the metal oxide thin film whose appearance and composition are controllable according to claim 1, it is characterized in that: described chemical corrosion oxidation is various metal corrosion oxidation processes, adopts chemical solution corrosion, atmospheric corrosion or Electrochemical oxidation corrosion. 4. The method for preparing a metal oxide thin film with controllable morphology and composition according to claim 1, characterized in that: the crystallization heat treatment temperature is 300-1000°C, and the heating rate is 0.1-10°C/min , The crystallization time is 0.5-48 hours. 5. The method for preparing a metal oxide thin film with controllable morphology and composition according to claim 4, characterized in that: preferably, the crystallization heat treatment temperature is 500-800°C, and the heating rate is 1-5 °C/min, the crystallization time is 1-24 hours. 6 . The method for preparing a metal oxide thin film with controllable morphology and composition according to claim 1 , characterized in that: the partial pressure of oxygen in the crystallization treatment is 0-10 ⁵ Pa. 7. The method for preparing a metal oxide thin film with controllable morphology and composition according to claim 6, characterized in that: preferably, the partial pressure of oxygen in the crystallization treatment is 0-1000Pa.