KR101753227B1 - Preparation method of black zirconia and the black zirconia using the same - Google Patents
Preparation method of black zirconia and the black zirconia using the same Download PDFInfo
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Abstract
The present invention relates to a process for producing black zirconia and black zirconia prepared using the same. The method of producing black zirconia (ZrO 2-x ) is a method of reducing heat by using magnesium (Mg), and it is possible to easily obtain reduced black zirconia (ZrO 2 -x ) There are advantages. In addition, black zirconia (ZrO 2-x ) prepared by the above method has an advantage that it can be used as a photocatalyst which is excellent in the light absorbing ability in the visible light region and has excellent photocatalytic performance and is active in the sunlight.
Description
The present invention relates to a process for producing black zirconia and black zirconia prepared using the same.
With the depletion of fossil energies and the interest in environmentally friendly energy, research has been conducted to convert solar energy, which is free from carbon emissions and has an infinite amount of energy, into chemical energy. Thus, Or photocatalysts that can be synthesized have been actively studied.
The photocatalytic reaction is a catalytic reaction using light. The photocatalyst absorbs light and excites electrons from the valence band to the conduction band. Electrons and holes are generated on the surface of the photocatalyst It is a reaction that decomposes or synthesizes a substance by reducing and oxidizing the adsorbed substance. The photocatalyst material causing the photocatalytic reaction is an oxide semiconductor such as TiO 2 , ZnO, CdS, ZrO 2 or the like, and the oxide semiconductor can cause a photocatalytic reaction by absorbing light having an energy of an energy band or more inherent to the oxide semiconductor . However, the photocatalyst currently being studied mainly has a problem in that it can absorb light in the ultraviolet ray region, but has a small absorption in the visible ray region and is limited in using solar energy as a photocatalytic energy source.
Recently, research has been conducted to produce an oxide semiconductor that exhibits catalytic activity by absorbing visible light, which is lower in energy band than ultraviolet light. For this purpose, a method of reducing an energy band gap of an oxide semiconductor to absorb visible light Research is underway to produce oxide semiconductors.
In the related art, Korean Patent Laid-Open No. 10-0924515 discloses a method for producing a visible-light-responsive anatase titanium oxide (TiO 2 ) photocatalyst. More specifically, the present invention relates to an anatase titanium oxide (TiO 2 ) capable of exhibiting photo-resolving power in the visible light region by lowering the bandgap of anatase titanium oxide (TiO 2 ) by doping carbon dioxide and fluorine into anatase titanium oxide (TiO 2) ) Discloses a method for producing a photocatalyst.
In addition, Journal of Materials Chemistry A, 2701 (2015.03) discloses a conventional technique for producing zirconia (ZrO 2 ) capable of absorbing visible light, wherein iron is doped to lower the band gap of zirconia (ZrO 2 ) A manufacturing method for producing zirconia (ZrO 2 ) capable of absorbing visible light has been disclosed.
However, in the method of doping the oxide semiconductor as described above, various defects may occur due to charge imbalance in the form of containing another metal or a non-metal element in the oxide semiconductor, and the photocatalytic activity is also insufficient.
On the other hand, zirconia (ZrO 2 ) has a band gap of about 5 eV, which is a very wide oxide semiconductor, and its application as a photocatalyst using solar light is very limited.
Accordingly, the present inventors have found that a method of thermally reducing zirconia (ZrO 2 ) using magnesium (Mg) to produce stable zirconia having excellent visible light absorption characteristics and using it as a solar photocatalyst, (ZrO2 -x ), and have completed the present invention.
It is an object of the present invention to provide a process for producing black zirconia and black zirconia produced using the same.
In order to achieve the above object,
Preparing a mixture by mixing zirconia (ZrO 2 ) and magnesium (Mg) (step 1); And
(ZrO2 -x ) comprising the step of heat-treating the mixture (step 2).
In addition,
The present invention provides black zirconia (ZrO 2-x ), which is produced by the above production method and has a band gap of 1.0 eV to 2 eV.
Further,
A photocatalyst containing black zirconia (ZrO 2-x ) and a novel material.
A method of producing black zirconia (ZrO 2-x ) of the present invention is a method of thermally reducing zirconia (ZrO 2 ) by using magnesium (Mg), which comprises adding reduced black zirconia (ZrO 2-x ) Can be easily obtained. In addition, black zirconia (ZrO 2-x ) prepared by the above method is advantageous in that it can be used as a photocatalyst that is active in sunlight because of its excellent light absorbing ability and photocatalytic performance in the visible light region. In addition, the electrical conductivity can be improved and used for various electrochemical reactions.
FIG. 1 is a photograph showing the result of observation of the color of zirconia produced according to the comparative example and the example by meat music.
FIG. 2 is a graph showing the results of X-ray diffraction (XRD) analysis of zirconia produced according to Comparative Examples and Examples,
FIG. 3 is a graph showing the results of analysis of zirconia prepared according to Comparative Examples and Examples by Raman spectroscopy (raman)
4 is a photograph showing the result of observation of zirconia produced according to the embodiment with a high-resolution transmission electron microscope (HR-TEM).
FIG. 5 is a histogram showing the degree of defect in an image obtained by observing zirconia produced according to the embodiment with a high-resolution transmission electron microscope (HR-TEM)
FIG. 6 is a graph showing the results of X-ray photoelectron spectroscopy (XPS) analysis of zirconia produced according to Comparative Examples and Examples,
FIG. 7 is a graph showing the results of thermogravimetric analysis (TGA) of zirconia prepared according to Comparative Examples and Examples,
FIG. 8 is a graph showing the results of X-ray photoelectron spectroscopy (XPS) analysis of zirconia prepared according to Comparative Examples and Examples in the entire energy range of 1200 eV, FIG. 7 (a)
9 is a graph showing the results of X-ray photoelectron spectroscopy (XPS) of zirconia prepared according to Comparative Examples and Examples in the energy region of magnesium 1s,
10 is a graph showing the results of ultraviolet-visible absorption (UV-VIS absorption) analysis of zirconia prepared according to Comparative Examples and Examples,
11 is a graph showing the results of ultraviolet-visible absorption (UV-VIS absorption) analysis of zirconia prepared according to the embodiment, and FIG.
FIG. 12 shows a Tauc plot for measuring the band gap,
FIG. 13 is a graph showing the results of X-ray photoelectron spectroscopy (XPS)
14 is a schematic diagram showing a band energy diagram,
15 is a schematic view showing a conventional unit cell of zirconia,
16 is a schematic view showing a unit cell of oxygen deficient black zirconia of the present invention,
17 shows band gaps calculated by using density functional theory (DFT) method of conventional zirconia and black zirconia of the present invention,
FIG. 18 shows the results of optical luminescence (PL) analysis of zirconia prepared according to Comparative Examples and Examples,
FIG. 19 is a graph showing decomposition performance of rhodamine B (RhB) obtained by evaluating photocatalytic performance using zirconia prepared according to Comparative Examples and Examples,
FIG. 20 is a graph showing the results of evaluating photocatalytic performance using zirconia prepared according to Comparative Examples and Examples,
21 is a graph showing the photocatalyst stability of zirconia produced according to the embodiment,
22 is a graph showing a comparison of the performance of hydrogen synthesis using zirconia produced with different magnesium contents,
23 is a bar graph comparing the hydrogen production rates of zirconia produced according to the comparative example and the example.
The term "black zirconia " as used throughout this specification refers to zirconia having a black-based color and some oxygen removed from the crystal structure and having the formula ZrO 2 -x wherein x is a rational number within the range of 0.01 to 2 . ≪ / RTI > In addition, the black zirconia (ZrO 2-x ) is a reduced or oxygen-deficient zirconia (ZrO 2-x ) having the same phase as that of conventional zirconia (ZrO 2 ) and containing zirconium (Zr) to be.
The present invention
Preparing a mixture by mixing zirconia (ZrO 2 ) and magnesium (Mg) (step 1); And
(ZrO2 -x ) comprising the step of heat-treating the mixture (step 2).
Hereinafter, the method for producing black zirconia (ZrO 2 -x ) according to the present invention will be described in detail for each step.
In the method for producing black zirconia (ZrO 2 -x ) of the present invention,
Here, the zirconia (ZrO 2 ) and magnesium (Mg) are not particularly limited, and commercially produced ones may be used. The zirconia (ZrO 2 ) and magnesium (Mg) may be mixed using a stirrer.
In this case, the molar ratio of magnesium (Mg) to zirconia (ZrO 2 ) is preferably 0.1 to 2.0, more preferably 0.5 to 1.5. The magnesium (Mg) is used for reducing zirconia (ZrO 2 ). When the zirconia (ZrO 2 ) and magnesium (Mg) are heat-treated in a reducing atmosphere, magnesium oxide (MgO) a ZrO 2) it may be reduced to black zirconia (ZrO 2-x). At this time, the oxygen content in the black zirconia (ZrO 2 -x) made in accordance with the amount of the magnesium (Mg) may vary, whereby the optical absorption characteristics of the black zirconia (ZrO 2-x) and a photocatalyst produced in accordance with the performance and electrical Chemical properties may vary.
If the zirconia (ZrO 2), if included over magnesium less than a molar ratio of 0.5 of the (Mg), the reducing degree of the property that small absorption of visible light of zirconia (ZrO 2), and may be insufficient, and the zirconia (ZrO 2) In the case where the molar ratio of magnesium to magnesium exceeds 1.5, it is confirmed by Examples and Experimental Examples that excessive oxygen defects are generated so that recombination of electrons and holes increases, the structure becomes unstable, and the photocatalytic property decreases. Accordingly, when the molar ratio of magnesium (Mg) to zirconia (ZrO 2 ) is in the range of 0.5 to 1.5, the light absorption characteristics and photocatalytic performance against visible light can be further improved.
In the method for producing black zirconia (ZrO 2 -x ) of the present invention, the
At this time, the heat treatment is preferably performed in an atmosphere in which hydrogen (H 2 ) is supplied, and may be performed at a temperature of 200 to 700 ° C., but it is most preferably performed at 300 to 700 ° C. This is for reducing zirconia (ZrO 2 ). When hydrogen is supplied during the heat treatment, black zirconia (ZrO 2-x ) can be produced at a lower temperature than that when hydrogen is supplied. The heat treatment may be performed in an atmosphere containing about 5% of hydrogen (H 2 ) in argon (Ar), but the content of hydrogen (H 2 ) is not limited thereto.
Meanwhile, the method for producing black zirconia (ZrO 2-x ) may further include a step of treating with acid after the heat treatment. (MgO) or other magnesium (Mg) components formed in the process of reducing zirconia (ZrO 2 ) can be removed by etching the heat-treated mixture with an acid. Thus, magnesium (ZrO2 -x ) can be produced. The step of treating with the acid may be carried out by stirring in a 2.0 M HCl solution for 24 hours, but the method of treating with the acid is not limited thereto.
Thereafter, the acid-treated mixture is washed with water to remove the acid, and then dried at 80 to recover black zirconia (ZrO 2-x ).
The method of producing black zirconia (ZrO 2-x ) comprises forming MgO and hydrogen (H 2 ) to form a reduced atmosphere, and then heat-treating the zirconia (ZrO 2 ) oxygen vacancy is formed to produce reduced zirconia, that is, black zirconia (ZrO 2-x ). (ZrO 2 ) can be reduced at a relatively low temperature of 300 to 700 ° C. by including magnesium (Mg) as a reducing agent, and black zirconia (ZrO 2 -x ) can be produced by a simpler method . In addition, the above manufacturing method can produce black zirconia (ZrO 2 -x ) having a band gap of about 1.5 eV, and by controlling the mixing amount of the magnesium to control the band gap size, There is an advantage that black zirconia (ZrO 2-x ) as a photovoltaic catalyst having excellent performance can be produced.
In addition, the black zirconia (ZrO 2) production method may include a method of manufacturing zirconia, titania, silica, ZnO, Fe 2 O 3 , SnO 2 , Al 2 O 3 , RuO, SrTiO 3 , and the like , thereby making it possible to produce various black metal oxides.
In addition,
The present invention provides black zirconia (ZrO 2-x ), which is produced by the above production method and has a band gap of 1.0 eV to 2 eV.
Hereinafter, the black zirconia (ZrO 2-x ) of the present invention will be described in detail.
The black zirconia (ZrO 2-x ) is an oxide semiconductor capable of absorbing visible light.
The oxide semiconductor photocatalyst, which absorbs light and activates the chemical reaction, has a wide bandgap, and has a large optical activity in the ultraviolet region (UV), but its activity in the visible region is limited and the use of the solar energy is limited .
Especially, the conventional zirconia (ZrO 2 ) is an important oxide semiconductor widely used in coatings, sensors, catalysts, energy storage and biomedical applications, but has a wide band gap of about 5 eV. It is difficult to use it as a photocatalyst in sunlight.
On the other hand, the black zirconia (ZrO 2-x ) of the present invention exhibits a low band gap of 1.5.eV, so that it can absorb light even in the visible light region and can be used as a photocatalyst in sunlight. In addition, the black zirconia (ZrO 2-x ) is structurally similar to conventional white zirconia (ZrO 2 ) but lacks oxygen in the lattice, and is stable zirconia with excellent visible light absorption property and photocatalytic property, And can be used in various fields such as sensors, coatings, energy storage, and biomedical applications
Further,
The present invention provides a photocatalyst comprising black zirconia (ZrO 2-x ) and absorbing visible light.
The photocatalyst can absorb visible light and can be a photocatalyst having improved activity against sunlight than a conventional photocatalyst. Accordingly, the photocatalyst can be used for hydrogen synthesis and decomposition of harmful compounds such as Rhodamine B (RhB), which can be very usefully used in solar photocatalyst applications.
Hereinafter, the present invention will be described in detail with reference to Examples and Experimental Examples.
However, the following Examples and Experimental Examples are merely illustrative of the present invention, and the contents of the present invention are not limited by the following Examples.
≪ Example 1 >
Black zirconia (ZrO 2-x ) was prepared by the following steps.
Step 1: Mixtures were prepared by mixing powders of nano-zirconia (ZrO 2 ) from Aldrich and magnesium (Mg) powders.
At this time, the molar ratio of magnesium (Mg) to zirconia (ZrO 2 ) of the mixture was set to 1.
Step 2: The mixture was placed in a furnace and heat treated in a 5% H 2 / Ar atmosphere and 650 ° C for 5 hours.
Step 3: The heat-treated mixture was stirred for 24 hours in a 2.0 molar HCl solution. The acid was then removed by washing with water and dried at 80 to prepare black zirconia (ZrO 2-x ).
≪ Example 2 >
Black zirconia (ZrO 2-x ) was prepared in the same manner as in Example 1 except that the molar ratio of magnesium (Mg) to zirconia (ZrO 2 ) in the mixture in Example 1 was 0.5.
≪ Example 3 >
Black zirconia (ZrO 2-x ) was prepared in the same manner as in Example 1 except that the molar ratio of magnesium (Mg) to zirconia (ZrO 2 ) in the mixture in Example 1 was 1.3.
<Example 4>
Black zirconia (ZrO 2-x ) was prepared in the same manner as in Example 1, except that the step of stirring in HCl solution for 24 hours in Example 3 was not carried out.
≪ Example 5 >
In order to perform heat treatment without containing hydrogen (H 2 ) in Example 1,
Black zirconia (ZrO 2-x ) was prepared in the same manner as in Example 1, except that hydrogen (H 2 ) was not contained in
≪ Comparative Example 1 &
Nd ZrO 2 powder from Aldrich
≪ Comparative Example 2 &
In order to perform the heat treatment without containing magnesium (Mg) and hydrogen (H 2 ) in Example 1,
Black Zirconia (ZrO 2-x ) was prepared by charging a nano-zirconia (ZrO 2 ) powder of Aldrich into a furnace and heat-treating it in an Ar atmosphere and 650 ° C for 5 hours.
≪ Comparative Example 3 &
In order to perform the heat treatment without containing magnesium (Mg) in Example 1,
Black Zirconia (ZrO 2-x ) was prepared by charging a nano-zirconia (ZrO 2 ) powder of Aldrich into a furnace and heat-treating it in a 5% H 2 / Ar atmosphere and 650 ° C. for 5 hours.
<Experimental Example 1> Color comparison
The black zirconia (ZrO 2 -x) made according to the present invention and a conventional zirconia (ZrO 2), Examples 1 to 3 The black zirconia (ZrO 2 -x) produced by the comparison to the color of Comparative Example 1 and Zirconia (ZrO 2 ) was visually observed, and the results are shown in FIG.
1, black zirconia (ZrO 2-x ) produced in Examples 1 to 3 was white in color in Comparative Example 1, which is a conventional zirconia (ZrO 2 ), but dark gray or black Black zirconia (ZrO 2-x ) produced in Example 1 is darker than black zirconia (ZrO 2-x ) prepared in Example 3, but black zirconia (ZrO 2-x ) prepared in Example 1 is darker.
As a result, the prepared black zirconia (ZrO 2-x ) has a black color, unlike conventional zirconia (ZrO 2 ), and a darker black with a higher magnesium content. In addition, since darkness means that the absorbance of the visible light ray is high, the higher the magnesium (Mg) content is, the higher the absorbance of the visible ray region is.
≪ Experimental Example 2 > X-ray diffraction analysis (1) -phase analysis
To compare the phase of the black zirconia (ZrO 2 -x) and a conventional zirconia (ZrO 2) prepared according to the present invention, Comparative Example 1, Example 1 and Example 4, the black zirconia (ZrO 2- prepared by x ) was performed as follows.
First, conventional zirconia (ZrO 2) and a black zirconia (ZrO 2 -x) prepared by Example 1 to compare the phase of the black zirconia (ZrO 2-x) of the present invention and of Comparative Example 1 zirconia (ZrO 2 ) were analyzed using an X-ray diffractometer (XRD), and black zirconia (ZrO 2-x ) prepared in Examples 1 and 4 was analyzed with X Ray diffractometer (XRD).
At this time, the X-ray diffraction analysis was carried out at 40 kV and 30 mA using Cu-Kα (0.15406 nm) at a scan rate of 4 ° min -1, and the results are shown in FIG.
As shown in Fig. 2, it can be seen that zirconia produced by Comparative Example 1 and Example 1 are the same phase.
Accordingly, it can be seen that black zirconia (ZrO 2-x ) prepared according to the production method of the present invention is the same phase as zirconia (ZrO 2 ).
On the other hand, in the case of the black zirconia (ZrO 2-x ) prepared in Example 4 in which the process of stirring in the HCl solution was not performed for 24 hours, magnesium oxide (MgO) was detected, It is not detected in the case of black zirconia (ZrO 2-x ).
This is because magnesium oxide (MgO) was produced in Examples 1 and 4 in which zirconia (ZrO 2 ) and magnesium (Mg) were mixed and heat-treated, and then magnesium oxide (MgO) , But it can be regarded as being detected because it was not removed in Example 4.
As a result, magnesium (Mg) is oxidized and zirconia (ZrO 2 ) is reduced in the heat treatment process to produce black zirconia (ZrO 2-x ) having oxygen vacancy.
Experimental Example 3 X-ray diffraction analysis (2) - Grain size analysis
To compare the phase of the black zirconia (ZrO 2 -x) and a conventional zirconia (ZrO 2) prepared according to the present invention, for the comparative example 1, and carrying out the black zirconia (ZrO 2-x) prepared by Example 1 The following experiment was carried out.
From the XRD results obtained in Experimental Example 2, the grain size was calculated using the Scherrer equation of the following
<
Dp: average grain size
β: Line broadening in radians
θ: Bragg angle
λ: X-ray wavelength
As shown in Table 1, it can be seen that the grain sizes of zirconia produced in Example 1 and Comparative Example 1 are similar to each other.
On the other hand, from the results of Experimental Example 2 and Experimental Example 3, black zirconia (ZrO 2-x ) produced according to the production method of the present invention has zirconia having the same phase and grain size as conventional white zirconia (ZrO 2 ) .
Experimental Example 4 Raman spectroscopy (Raman spectroscopy)
In order to compare the surface states of black zirconia (ZrO 2 -x ) and conventional zirconia (ZrO 2 ) produced according to the present invention, the following experiment was conducted.
Surface analysis was performed on black zirconia (ZrO 2 -x ) prepared in Example 1 and zirconia (ZrO 2 ) in Comparative Example 1 using a Raman spectrometer having a wavelength of 532 nm, and the results are shown in FIG. 3 .
In the case of zirconia (ZrO 2) of Comparative Example 1 as shown in Fig. 3,
Raman spectroscopy is an analytical method that shows the difference in the characteristics or shape of a material by Raman scattering which occurs when an energy having a certain energy is irradiated to a material. Especially, it is an analytical method useful for grasping atomic defects on a surface. The Raman embodiments black zirconia zirconia (ZrO 2) and results that are not receive the Raman peak in spite of the same standing in the comparative example 1 (ZrO 2-x) of the first is surface defects formed in the black zirconia (ZrO 2-x) . It can also be expected that this is due to the oxygen vacancy of black zirconia (ZrO 2-x ) produced by reduction of zirconia (ZrO 2 ).
<Experimental Example 5> High Resolution Transmission Electron Microscope (HR-TEM) Analysis
In order to compare the surface states of black zirconia (ZrO 2-x ) produced according to the present invention, the following experiment was conducted.
Surface analysis of black zirconia (ZrO 2-x ) prepared in Example 1 was performed using a high - resolution transmission electron microscope (HR-TEM), and the results are shown in FIGS. 4 and 5.
Fig. 4 is an HR-TEM image of black zirconia (ZrO2 -x ) produced by Example 1, and Fig. 5 is a histogram showing the contrast of the image. At this time, a high-resolution transmission electron microscope (HR-TEM) image was used with JEOL FE-2010 operating at 200 kV.
It is seen that the Figure 4 and a defect (defect) is formed on the surface of the black zirconia (ZrO 2-x) prepared by Example 1 as shown in Figure 5, which for producing the black zirconia (ZrO 2-x) It can be expected that oxygen vacancy formed due to the reduction of zirconia (ZrO 2 ) in the process.
Experimental Example 6 X-ray photoelectron spectroscopy (XPS) (1)
In order to compare the oxygen atom bonding energies of black zirconia (ZrO 2 -x ) and conventional zirconia (ZrO 2 ) prepared according to the present invention, the following experiment was conducted.
The binding energy of oxygen atom 1s was compared between the black zirconia (ZrO 2 -x ) prepared in Example 1 and the zirconia (ZrO 2 ) in Comparative Example 1 using an X-ray photoelectron spectroscope. The results are shown in FIG. 6 The results of calculating the ratio of oxygen and oxygen vacancy from the above results are shown in Table 2 below. At this time, the X-ray photoelectron spectrometer was an
As shown in Fig. 6, the binding energy spectrum of the oxygen atom 1s can be divided into an oxygen atom bonding energy of 530.5 and a binding energy by oxygen vacancy of 531.9 eV, It can be seen that black zirconia (ZrO 2-x ) has more oxygen vacancies than zirconia (ZrO 2 ) of Comparative Example 1, and the ratio of oxygen vacancy As a result, as shown in Table 2 above, the amount of oxygen vacancies (ZrO 2 -x ) prepared in Example 1 was larger than that of zirconia (ZrO 2 ) of Comparative Example 1 having 43% in 71% for black zirconia (oxygen vacancy) is formed.
The oxygen vacancy is generated by reducing zirconia (ZrO 2 ). Thus, the black zirconia (ZrO 2-x ) produced according to the present invention is reduced in zirconia (ZrO 2 ) It can be seen that zirconia has many oxygen vacancies on its surface.
Experimental Example 7 Thermogravimetric analysis (TGA)
In order to confirm the oxygen deficiency state of black zirconia (ZrO 2-x ) produced according to the present invention, the following experiment was conducted.
(ZrO 2-x ) prepared in Example 1 and zirconia (ZrO 2 ) in Comparative Example 1 were heated to 0 to 700 ° C in an atmosphere in which oxygen (O 2 ) was supplied using a thermogravimetric analyzer The results are shown in FIG. 7,
As shown in Fig. 7, in the case of zirconia (ZrO2 -x ) produced by Comparative Example 1, there was no increase in weight in the temperature raising process, while in the case of black zirconia (ZrO2 -x ) , The weight increases. It can be seen that black zirconia (ZrO 2-x ) appears as it absorbs oxygen during the heating process, indicating that black zirconia (ZrO 2 -x ) exists in an oxygen deficient state.
<Experimental Example 8> X-ray photoelectron spectroscopy (XPS) (2)
The following experiment was conducted to confirm the presence or absence of magnesium (Mg) in the black zirconia (ZrO 2 -x ) produced according to the present invention and to compare the components with the conventional zirconia (ZrO 2 ).
Black Zirconia (ZrO 2 -x ) prepared in Example 1 and zirconia (ZrO 2 ) in Comparative Example 1 were subjected to X-ray photoelectron spectroscopy to obtain signals at 0 to 1200 eV and signals corresponding to Mg 1s binding energy The results are shown in Figs. 8 and 9. At this time, the X-ray photoelectron spectrometer was an
Zirconia (ZrO 2) of Example 1, a black zirconia (ZrO 2-x) produced by and Comparative Example 1 As shown in Figures 8 and 9 were naeteot receive the same signal from 0 to 1200 eV, magnesium (Mg ) 1s signal did not appear.
Thus, it can be seen that magnesium is not present in the black zirconia (ZrO 2 -x ) and contains the same components as zirconia (ZrO 2 ), that is, zirconium (Zr) and oxygen (O).
Experimental Example 9 UV-VIS absorption analysis
In order to compare the light absorption characteristics of black zirconia (ZrO 2 -x ) and conventional zirconia (ZrO 2 ) produced in accordance with the present invention in ultraviolet and visible light, the following experiment was conducted.
Example 1 The black zirconia (ZrO 2 -x) prepared by Comparative Examples 1 to 3 and zirconia (ZrO 2) to Agilent Technology is a Ultraviolet-Visible-Near Infrared Spectrophotometer using (CARY5000) absorption spectrum (absorption preparation of spectra were obtained, and the results are shown in FIGS. 10 and 11.
As shown in FIG. 10, the zirconia (ZrO 2 ) of Comparative Example 1 exhibited unique light absorption characteristics at a wavelength of about 246 nm, which is the ultraviolet region, whereas that of the black zirconia (ZrO 2 -x ) , It can be confirmed that it exhibits excellent light absorption characteristics in the visible and infrared regions. 11, the black zirconia (ZrO2 -x ) prepared in Example 1 was higher than the black zirconia (ZrO2 -x ) prepared in Example 2, and the black zirconia (ZrO 2-x ) has a larger amount of light absorption than black zirconia (ZrO 2 -x ) prepared in Example 1.
As a result, it can be seen that black zirconia (ZrO 2-x ) produced according to the production method of the present invention is excellent in light absorption properties of visible light and ultraviolet light, and in producing black zirconia (ZrO 2 -x ) (Mg) content is higher, the light absorption property is further improved.
Experimental Example 10 Measurement of band gap
The following experiments were conducted to determine the band gaps of black zirconia (ZrO 2 -x ) and conventional zirconia (ZrO 2 ) prepared according to the present invention.
Absorption spectra were measured using Ultraviolet-Visible-Near Infrared Spectrophotometer (CARY5000) manufactured by Agilent Technology, black zirconia (ZrO 2 -x ) prepared in Example 1 and zirconia (ZrO 2 ) And a Tauc plot was obtained from the above results. The band gap was determined. The results are shown in FIG. At this time, the tau graph is a graph showing the light absorption amount with respect to the light energy, and the energy band gap can be obtained by a method of linear extrapolating the slope of the graph to the energy axis.
13 shows an XPS graph comparing the upper positions of the valence band of the black zirconia (ZrO 2 -x ) produced in Example 1 and the zirconia (ZrO 2 ) of Comparative Example 1, FIG. 14 is a graph showing band energy diagrams in consideration of the position of the valence band and the bandgap.
12, in the case of zirconia (ZrO 2 ) of Comparative Example 1, a band of about 5.09 eV and a band of 4.55 eV in the case of black zirconia (ZrO 2 -x ) produced by Example 1 Gap and a tuned bandgap of 1.5 eV.
13, the energies of valence bands of black zirconia (ZrO 2-x ) and zirconia (ZrO 2 ) of Comparative Example 1 produced by Example 1 were 1.24 and 4.11 .
As shown in FIG. 14, black zirconia (ZrO 2 -x ) produced according to the present invention has a band gap narrower than that of zirconia (ZrO 2 ) as a result of increasing the valence band position , And the change in the energy band gap can be attributed to oxygen vacancies formed on the surface of the black zirconia (ZrO 2 -x ).
EXPERIMENTAL EXAMPLE 11 Band Gap Calculation Using Density Functional Theory (DFT) Method.
The atomic positions are modeled to theoretically determine the band gap of black zirconia (ZrO 2 -x ) and conventional zirconia (ZrO 2 ) produced according to the present invention, and the results are shown in FIGS. 15 and 16, The band gap was calculated using the density functional theory (DFT) method. The results are shown in the upper part of FIG. 17 in the conventional zirconia and the lower part in FIG. 17 in the black zirconia (ZrO 2-x ) of the invention.
First, as shown in FIGS. 15 and 16, the positions of the atoms are shown such that conventional zirconia (ZrO 2 ) exists in 12 monoclinic unit cells, and black zirconia (ZrO 2 -x ) has the same structure Assuming oxygen vacancies in the monoclinic unit cell,
As shown in FIG. 17, the band gap of conventional zirconia (ZrO 2 ) and black zirconia (ZrO 2 -x ) of the present invention were 5.14 eV and 1.55 eV, respectively, The results are almost the same as the values measured through Example 4.
EXPERIMENTAL EXAMPLE 12 Measurement of Photoluminescence (PL)
The following experiment was conducted to measure the photoluminescence (PL) of black zirconia (ZrO 2 -x ) and conventional zirconia (ZrO 2 ) produced according to the present invention.
Black zirconia (ZrO 2 -x ) prepared in Example 1 and zirconia (ZrO 2 ) in Comparative Example 1 were dispersed in ethanol (1 mg / 5 ml), excitation wavelengths were 270 nm and 5 nm slit was used to obtain a photoluminescence (PL) spectrum, and the results are shown in Fig.
At this time, the intensity of the optical luminescence (PL) is related to the recombination of electrons and holes, and the high intensity shows fast recombination.
As shown in FIG. 18, black zirconia (ZrO 2-x ) produced according to the example exhibited a peak at the same position as zirconia (ZrO 2 ), but showed a very strong intensity.
As a result, it can be expected that the recombination of electrons and holes formed in the black zirconia (ZrO 2-x ) produced according to the present invention is slowed to increase the photoactive efficiency.
<Experimental Example 13> Evaluation of photocatalytic activity (1) - Evaluation of Rhodamine B (RhB) removal performance
The following experiments were carried out to measure the photocatalytic activity of black zirconia (ZrO 2 -x ) and rhodamine B (RhB) of zirconia (ZrO 2 ) prepared according to the present invention.
(ZrO 2-x ) prepared in Example 1 and zirconia (ZrO 2 ) in Comparative Example 1 were dispersed in 50 ml of a solution having a concentration of 1 ppm rhodamine B (RhB) to prepare a mixed solution. The prepared mixed solution was immersed in a glass container and irradiated with sunlight for about 60 minutes under a condition of stirring under a light of a total solar wavelength using a 100 W Xenon lamp with a 1.5 G filter The amount of decrease in rhodamine B (RhB) over time was measured, and the results are shown in FIG.
(ZrO 2-x ) prepared in Example 1, while the concentration of rhodamine B (RhB) was not changed when zirconia (ZrO 2 ) of Comparative Example 1 was used as a photocatalyst, Was used as the photocatalyst, the concentration of the rhoramine B (RhB) was considerably reduced.
Thus, it can be seen that the black zirconia (ZrO 2-x ) produced according to Example 1 can absorb visible light, which is a substantial part of the sunlight, and thus acts as a photocatalyst that catalytically activates sunlight.
<Experimental Example 14> Hydrogen generation performance evaluation (1) - Evaluation of photocatalytic activity
The following experiments were conducted to measure the photocatalytic activity of black zirconia (ZrO 2 -x ) and conventional zirconia (ZrO 2 ) produced according to the present invention through water (H 2 O) -generated amount of hydrogen (H 2 ) Respectively.
Preparation of Pt-deposited photocatalyst
Black zirconia (ZrO 2 -x ) prepared in Example 1 and zirconia (ZrO 2 ) of Comparative Example 1 were placed in a closed gas circulation system and 50 ml of a 20% methanol aqueous solution and H 2 PtCl 6 . (ZrO 2 -x ) and zirconia (ZrO 2 ) photocatalysts were prepared by irradiating ultraviolet rays (UV) in an Ar atmosphere by adding an appropriate amount of 6H 2 O.
Experimental method of hydrogen generation
50 mg of the black zirconia (ZrO 2 -x ) and zirconia (ZrO 2 ) photocatalyst on which Pt (1 wt% or less) was deposited on the closed gas circulation system was added to an aqueous methanol solution (50 ml, 20% The light of the entire solar wavelength was irradiated for 250 minutes using a 100 W Xenon lamp with a built-in filter. At this time, methanol was used as the sacrificial reagent and the amount of H 2 produced was determined by on-line gas chromatography (
As shown in FIG. 20, when zirconia (ZrO 2 ) of Comparative Example 1 was used as a photocatalyst, no hydrogen was produced, whereas black zirconia (ZrO 2 -x ) prepared in Example 2 was hydrogenated at a hydrogen production rate of 381 μmolg -1 h -1 . ≪ / RTI >
Thus, it can be seen that the black zirconia (ZrO 2-x ) produced according to Example 1 can absorb visible light, which is a substantial part of the sunlight, and thus acts as a photocatalyst that catalytically activates sunlight.
<Experimental Example 15> Hydrogen generation performance evaluation (2) - Evaluation of photocatalyst stability
In order to confirm the photocatalytic stability of black zirconia (ZrO 2-x ) prepared according to the present invention, the following experiment was conducted.
Pt was deposited on the black zirconia (ZrO 2 -x ) prepared in Example 1 by the deposition method performed in Experimental Example 14, and then, by the same method as in the hydrogen generation method of Experimental Example 14, The photocatalytic stability of black zirconia (ZrO 2-x ) was evaluated by repeating the experiment for 30 days and then for 2 hours at 30 days after storage for 23 days in the standby state. The results of measuring the amount of hydrogen generated by irradiation with time are shown in FIG.
As shown in FIG. 21, it can be seen that the amount of hydrogen generated even when irradiating the entire solar wavelength continuously for 30 days is constant. Thus, it can be seen that the black zirconia (ZrO 2-x ) produced by Example 1 exhibits stable photocatalytic activity.
<Experimental Example 16> Hydrogen generation performance evaluation (3) - Performance evaluation according to magnesium (Mg) content
In the production method according to the present invention, the following experiment was conducted in order to compare the photocatalyst performance according to the content of magnesium mixed.
Pt was deposited on the black zirconia (ZrO 2-x ) prepared in Examples 1 to 3 by the vapor deposition method performed in Experimental Example 14, and then hydrogen generation experiment was carried out in the same manner as in Experimental Example 14 The results of measuring the amount of hydrogen generated as a result of time are shown in FIG.
As shown in FIG. 22, in the case of the black zirconia (ZrO 2-x ) prepared in Example 1 in which the molar ratio of zirconia and magnesium was 1: 1, the hydrogen production rate was 381 μmolg -1 h -1 High.
<Experimental Example 17> Hydrogen generation performance evaluation (4) - Performance evaluation according to manufacturing conditions
The following experiments were conducted to compare the photocatalytic performance according to the production conditions.
Pt was deposited on the black zirconia (ZrO 2 -x ) prepared in Examples 1 to 3 and 5 and the zirconia prepared in Comparative Examples 1 to 3 by the deposition method performed in Experimental Example 14, FIG. 23 shows the result of measurement of the rate of hydrogen generation occurring by performing hydrogen production experiment in the same manner as in the hydrogen production experiment of Example 14. FIG.
As shown in FIG. 23, in the case of black zirconia (ZrO 2-x ) produced by the methods of Examples 1 to 3, the hydrogen production rate was high, whereas when produced by Comparative Example 2 in which only Ar was used during heat treatment, It can be seen that a very small amount of hydrogen was produced when zirconia produced by Comparative Example 3 using only hydrogen and Example 5 using only magnesium was used.
In order to increase the photocatalytic activity in sunlight, black zirconia (ZrO 2-x ), which exhibits the highest photocatalytic efficiency when heat treatment includes both magnesium and hydrogen in the method of producing black zirconia (ZrO 2-x) ) Is produced.
Claims (10)
And heat treating the mixture (step 2)
Heat treatment of the step 2 is hydrogen (H 2) a method of manufacturing black zirconia (ZrO 2-x), characterized in that is carried out in the atmosphere to be supplied (ordination between glass wherein X is from 0.01 to 2).
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| US15/552,722 US11260368B2 (en) | 2015-09-30 | 2016-09-30 | Method for reducing metal oxide and method for producing photocatalyst using same |
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Non-Patent Citations (4)
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| J. AM. CHEM. SOC. 2012, 134, 7600-7603* |
| J. MATER. CHEM. A, 2015, 3, 2701-2706 |
| J. MATER. RES., VOL. 26, NO. 16* |
| MATERIALS LETTERS 57 (2003) 4023-4027 |
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