CN104108682B - A kind of have visible light-responded germanium hydride and its preparation method and application - Google Patents

Abstract

The invention relates to a germanium hydride with visible light response, a preparation method and application thereof. First, calcium germanium crystals are synthesized by melting co-solvent method, and the final product germanium hydride is obtained by ion exchange in the next step. The germanium hydride synthesized by the invention has a nanoscale layered structure, and the germanium hydride photocatalyst formed by it has strong absorption in the visible light region, and has strong photocatalytic activity, including photocatalytic hydrogen production and degradation of organic pollutants.

Description

A kind of germanium hydride with visible light response and its preparation method and application

technical field

The invention relates to a novel photocatalytic material, in particular to germanium hydride with visible light response and its preparation method and application.

Background technique

In recent years, with the aggravation of the global energy crisis and environmental pollution, hydrogen energy, as an effective carrier of solar energy, can effectively solve the problems of solar energy storage and transportation. Since 1972, Fijishima and Honda reported photo-induced water splitting on n-type semiconductor TiO ₂ single crystal electrodes to generate H ₂ and O ₂ , and the use of solar energy for photocatalytic water splitting to produce clean, efficient and renewable hydrogen has become more and more important. increasingly receiving global attention. The use of semiconductor photocatalysts to convert light energy into electrical energy and chemical energy has become one of the most active research fields in the world in recent years. Among them, photocatalytic water splitting for hydrogen production has attracted widespread attention of scientists from all over the world due to its unique advantages, and extensive theoretical and experimental research on it will have very important strategic and practical significance.

However, visible light accounts for about 43% of the solar spectrum, which is far greater than the proportion of ultraviolet light (3-4%). Therefore, the research and development of photocatalysts that respond to visible light and the full and efficient use of solar energy to produce hydrogen have become the focus of current research scholars. , is more practical.

The research and application of germanium hydride has become a research hotspot in recent years. "American Chemical Society" (ACSNano, 2013, 4414-4421), (ACSNano, 2013, 2898-2926) and "Journal of Chemical Physics" (THE JOURNALOFCHEMICALPHYSICS, 2013, 124709-5) reported that germanium hydride is a hydrogen terminal The multilayer graphane analog of germanium and has a direct bandgap of 1.53eV. Therefore, the application of germanium hydride in the field of photocatalysis has important practical significance.

Contents of the invention

The purpose of the present invention is to provide a germanium hydride with visible light response and its preparation method and application. The material has strong absorption in the visible light region and has strong photocatalytic activity, including photocatalytic decomposition of water to produce hydrogen and photocatalytic Degradation of the organic dye rhodamine B.

The technical scheme that the present invention takes is as follows:

A method for preparing germanium hydride with visible light response, comprising the following steps:

1) The precursor calcium germanium is synthesized by the method of growing crystals using melting flux: in a glove box filled with argon, the molar ratio of Ca, Ge, and Pb is Ca:Ge:Pb=0.7～1.5:2:20～25 Weigh the above three simple substances, put them into an alumina crucible after mixing, and seal the alumina crucible in a quartz glass tube with high vacuum-line operation technology (vacuum-line), and heat the system to 1000°C within 4 hours in the heating furnace And keep it warm for 18-22 hours, then cool down to 600°C at a rate of 3-7°C per hour, and keep warm for 10-15 hours; then take out the glass tube, put it upside down in a centrifuge and centrifuge to separate the molten flux lead And collect, and pick out the flaky crystal precursor calcium germanide under the microscope in the glove box;

2) The precursor calcium germanium is reacted with concentrated hydrochloric acid in a low-temperature constant-temperature ethanol bath at -30°C for 24-48 hours, then naturally returned to room temperature, centrifuged, washed, and dried.

Preferably, the molar ratio relationship is Ca:Ge=1:2.

The centrifugal speed described in step (1) is 3000-3500 rev/min.

In step (2), the ratio of the precursor calcium germanium to the concentrated hydrochloric acid is 0.2:100, g/ml; the mass concentration of the concentrated hydrochloric acid is 37%. The germanium hydride with visible light response prepared by the above method has a layered structure. The hydrogen production rate under visible light is 22μmol·h ^-1 ·g ^-1 .

The application of the germanium hydride with visible light response as a catalyst in the visible light catalytic decomposition of water to generate hydrogen.

A germanium hydride photocatalyst contains the above-mentioned germanium hydride with visible light response, and is prepared under light.

The preparation method of the germanium hydride photocatalyst: add the germanium hydride sample into a mixed solution of deionized water and methanol, and load 1.0 wt% of the precious metal platinum on the germanium hydride mass, and use 300W to It is obtained by irradiating xenon lamp for 0.5-1 hour.

The amount of deionized water and methanol used is 20-30 milliliters of deionized water and 20-25 milliliters of methanol for every 50 mg of germanium hydride sample.

The invention uses germanium hydride, a photocatalytic material responsive to visible light, to produce hydrogen by photocatalytically decomposing water and to remove organic pollutants in air, waste water, surface water or drinking water.

The excellent effects of the present invention are as follows:

1. The photocatalytic material germanium hydride of the present invention has a layered structure, and the photocatalytic material responds to visible light.

2. The present invention exchanges the calcium in the calcium germanium with hydrogen through the ion exchange method, and reacts to form germanium hydride.

3. The obtained germanium hydride photocatalytic material shows good photocatalytic activity, can decompose water to produce 135umol of hydrogen in 6 hours, and degrade 82% of rhodamine B organic dyes in 4 minutes.

4. The conditions of the preparation and synthesis method of the photocatalytic material of the present invention are controllable, and have high commercial application prospects.

Experimental studies have found that germanium hydride shows good photocatalytic performance, and the photocatalyst prepared for photocatalytic decomposition of water to produce hydrogen can decompose water to produce 135umol of hydrogen after 6 hours of visible light irradiation. Can degrade 82% of rhodamine B organic dyes within 4 minutes. In contrast, the photocatalyst formed by nitrogen-doped P25 degrades rhodamine B by 70% within 30 min. Therefore, germanium hydride synthesized by ion exchange has higher activity compared with N-doped P25 in photocatalytic applications.

Description of drawings

Fig. 1 is the X-ray picture of the precursor of embodiment 1 of the present invention;

Fig. 2 is the X-ray picture of the product of embodiment 1 of the present invention;

Fig. 3 is the SEM figure of the product of embodiment 1 of the present invention;

Fig. 4 is the photocatalyst that the product of embodiment 1 of the present invention forms and nitrogen-doped P25 is used for the contrast figure of photocatalytic degradation organic dye rhodamine B;

Fig. 5 is the photocatalyst that the photocatalyst that the product of embodiment 1 of the present invention forms is used for photocatalytic decomposing water to produce hydrogen production figure;

Fig. 6 is the X-ray picture of the product of embodiment 2 of the present invention;

Figure 7 is a SEM image of the product of Example 2 of the present invention.

detailed description

The present invention will be further described below in conjunction with the accompanying drawings, but not limited thereto.

The method that prepared material is carried out photocatalytic activity test in the embodiment is as follows:

The photocatalytic water splitting hydrogen production test was carried out in a closed glass container system connected with circulating cooling water (5°C), and the vacuum condition was -97KPa. The light source illuminated on the top is a 300W xenon lamp equipped with a filter, so that the wavelength of the light source is greater than 420nm. Firstly, the samples were loaded with noble metal platinum (1.0wt%). Weigh 50mg of the sample and disperse it in 30ml of water and 20ml of methanol, measure 33ul of chloroplatinic acid solution (0.0772mM), and irradiate it with a 300W xenon lamp for 30 minutes under constant stirring. Before the photocatalytic decomposition of water to produce hydrogen, stir for 1 hour in the dark to eliminate the interference of residual gas. Subsequently, add a filter (λ≥420nm) for illumination. Test every 1h after the light is turned on, and the peak area value measured by the gas chromatograph is converted into the hydrogen production.

The photocatalytic degradation of organic dyes was tested in a glass beaker (30 cm ² in cross section, 5 cm in height) at normal temperature and pressure. The light source is a 300W xenon lamp equipped with a filter, so that the wavelength of the light source is greater than 420nm. Rhodamine B was used to evaluate the photocatalytic activity of the samples. Weigh 50mg germanium hydride sample and disperse in 50ml rhodamine B solution (20mg/L). Before the photocatalytic reaction test, magnetically stir for 30 minutes in the dark to make Rhodamine B reach adsorption equilibrium on the surface of the catalyst. After the light is turned on, 5ml samples are taken every 2 minutes, centrifuged, and the supernatant is taken to measure the absorbance with a UV-Vis spectrophotometer.

Example 1

Weigh Ca: 0.0401g, Ge: 01452g, Pb: 5.1807g and put them into an alumina crucible of about 2cm ³ , and seal the alumina crucible in a quartz glass tube with a high vacuum line operation technology (vacuum-line). The system was heated to 1000°C within 4 hours and kept for 20 hours in a type furnace to ensure that the raw materials were fully reacted; then the temperature was lowered to 600°C at 3°C per hour and kept for 10 hours; then the glass tube was taken out and placed upside down In a centrifuge at 3,500 rpm, the molten flux lead is separated and collected. Under the microscope in the glove box, select the crystalline high-quality flaky calcium germanium crystal 0.2, and react with 100ml concentrated hydrochloric acid for 48 hours under constant stirring in a low-temperature and constant temperature reaction ethanol bath (reaction temperature is minus 30°C), and wait for natural Heat up to room temperature for suction filtration, wash with methanol and deionized water, and dry in a vacuum oven at room temperature for 8 hours to obtain the final product germanium hydride.

Accompanying drawing 1 is the X-ray diffraction figure of the precursor calcium germanide obtained in this embodiment, as can be seen from the figure, except that there is the miscellaneous peak of metal cosolvent lead, each diffraction peak of this precursor calcium germanide is all consistent with trigonal system germanium The peaks on the calcium standard card (JCPDSfileno.13-299) correspond to each other, and the diffraction peaks are stronger, indicating that the product is a calcium germanide crystal containing impurity lead. Accompanying drawing 2 is the X-ray diffraction figure of the final product germanium hydride obtained in this embodiment, as can be seen from the figure, each diffraction peak of this product germanium hydride all corresponds to the peak position on the literature (ACSNano, 2013,4414-4421) report, and the diffraction The peak is stronger, indicating that the product is pure germanium hydride. Accompanying drawing 3 is the SEM picture of the product germanium hydride obtained in this embodiment, as can be seen from the figure that the germanium hydride is a nano-layered structure. Accompanying drawing 4 is that the photocatalyst that the product obtained in this embodiment forms is used for photocatalytic degradation organic dye Rhodamine B, as can be seen from the figure, through photocatalytic degradation organic dye Rhodamine B test, the photocatalyst that the germanium hydride forms can decompose Rhodamine B in 4min Rhodamine B was degraded by 82%, and the photocatalyst formed by nitrogen-doped P25 degraded Rhodamine B by 70% in 30 minutes. It can be seen that germanium hydride synthesized by ion exchange has higher activity in photocatalytic applications than N-doped P25. Accompanying drawing 5 is that the photocatalyst that the product obtained in this example forms is used for photocatalytic decomposition of water to produce hydrogen. According to the test of hydrogen production by photocatalytic decomposition of water, the photocatalyst formed by germanium hydride can decompose water in 6 hours to generate 135umol of hydrogen.

The above detection and analysis comprehensively prove that the product obtained in this embodiment is a photocatalyst with visible light response for photocatalytic hydrogen production. The germanium hydride prepared by the method of the invention has strong visible light response after being converted into a photocatalyst, and has high photocatalytic activity, and has been effectively applied in the fields of photocatalytic decomposition of water to produce hydrogen, degradation of organic pollutants, and the like.

Example 2

Weigh Ca: 0.0407g, Ge: 01448g, Pb: 5.1795g and put them into a 2cm ³ alumina crucible, and seal the alumina crucible in a quartz glass tube with high vacuum line operation technology (vacuum-line). The furnace raises the temperature of the system to 1000°C within 4 hours and keeps it warm for 20 hours to ensure that the raw materials are fully reacted; then cools down to 600°C at 5°C per hour and keeps it warm for 8 hours; then the glass tube is taken out, inverted and placed in a centrifuge Inside the machine, the molten flux lead is separated and collected at a speed of 3,500 revolutions per minute. Under the microscope in the glove box, select 0.2g of crystalline high-quality flaky calcium germanide crystals, react with 100ml concentrated hydrochloric acid under constant stirring with a low-temperature constant temperature reaction ethanol bath for 48 hours (reaction temperature is minus 30°C), and wait for Naturally warm up to room temperature for suction filtration, wash with methanol and deionized water, and dry in a vacuum oven at room temperature for 6 hours to obtain the final product germanium hydride.

Accompanying drawing 6 is the X-ray diffraction diagram of the final product germanium hydride obtained in this embodiment, as can be seen from the figure, the product is pure germanium hydride. Accompanying drawing 7 is the SEM image of the product germanium hydride obtained in this embodiment, it can be seen from the figure that the germanium hydride has a nano-layered structure.

Example 3

Weigh Ca: 0.0411g, Ge: 01445g, Pb: 5.1802g and put them into a 2cm ³ alumina crucible, and seal the alumina crucible in the quartz glass tube by vacuum-line, and use the experimental box type The furnace raises the temperature of the system to 1000°C within 4 hours and keeps it warm for 20 hours to ensure that the raw materials are fully reacted; then cools down to 600°C at 5°C per hour and keeps it warm for 10 hours; then the glass tube is taken out, inverted and placed in a centrifuge Inside the machine, the molten flux lead is separated and collected at a speed of 3,500 revolutions per minute. Under the microscope in the glove box, select 0.2g of crystalline high-quality flaky calcium germanide crystals, and react with 100ml concentrated hydrochloric acid under constant stirring with a low-temperature and constant temperature reaction ethanol bath for 24 hours (reaction temperature is minus 30°C). Naturally warm up to room temperature for suction filtration, wash with methanol and deionized water, and dry in a vacuum oven at room temperature for 6 hours to obtain the final product germanium hydride.

Although the specific implementation of the present invention has been described above in conjunction with the accompanying drawings, it does not limit the protection scope of the present invention. Those skilled in the art should understand that on the basis of the technical solution of the present invention, those skilled in the art do not need to pay creative work Various modifications or variations that can be made are still within the protection scope of the present invention.

Claims (6)

1. a preparation method of germanium hydride with visible light response, is characterized in that, comprises steps as follows: 1) The precursor calcium germanium is synthesized by the crystal growth method of melting flux: in a glove box filled with argon, the molar ratio of Ca, Ge, and Pb is Ca:Ge:Pb=0.7～1.5:2:20～25 Weigh the above three simple substances, put them into an alumina crucible after mixing, seal the alumina crucible in a quartz glass tube, heat the system to 1000°C within 4 hours and keep it warm for 18-22 hours in the heating furnace, and then Cool down to 600°C at a speed of 3-7°C per hour and keep warm for 10-15 hours; then take out the glass tube, put it upside down and put it in a centrifuge to centrifuge to separate the molten flux lead and collect it under the microscope in the glove box Pick out the flaky crystal precursor calcium germanium; 2) The precursor calcium germanide is reacted with concentrated hydrochloric acid in a low-temperature constant-temperature ethanol bath at -30°C for 24-48 hours, then naturally returned to room temperature, centrifuged, washed, and dried; In the step (2), the ratio of the precursor calcium germanium to the concentrated hydrochloric acid is 0.2:100, g/ml; the mass concentration of the concentrated hydrochloric acid is 37%. 2. a kind of preparation method of the germanium hydride with visible light response according to claim 1, is characterized in that, described molar ratio relation is Ca:Ge=1:2. 3. A method for preparing germanium hydride with visible light response according to claim 1, characterized in that the centrifugal speed in step (1) is 3000-3500 rpm. 4. The germanium hydride prepared by the method according to any one of claims 1-3, characterized in that it has a layered structure. 5. The germanium hydride described in claim 4 is used as a catalyst in visible light catalytic decomposition of water to produce hydrogen. 6. a germanium hydride photocatalyst, contains the germanium hydride described in claim 4, and makes under illumination: The germanium hydride sample is added to a mixed solution of deionized water and methanol, and the precious metal platinum is loaded with 1.0 wt% of the germanium hydride mass, and it is obtained by irradiating with a 300W xenon lamp for 0.5-1 hour under constant stirring; The amount of deionized water and methanol used is 20-30 milliliters of deionized water and 20-25 milliliters of methanol for every 50 mg of germanium hydride sample.