CN104399449A - Visible light responsive photocatalyst Li2GaB3O7 and its preparation method - Google Patents

Abstract

The invention discloses a visible light responsive photocatalyst Li ₂ GaB ₃ O ₇ and a preparation method thereof. The chemical composition formula of the photocatalyst is Li ₂ GaB ₃ O ₇ . The invention also discloses a preparation method of the above material. The photocatalyst obtained by the invention has the advantages of wide spectral response range, high light conversion efficiency, good stability and the like. It has the functions of decomposing harmful chemical substances, organic biomass and sterilizing under the irradiation of visible light; in addition, the preparation method is simple, the synthesis temperature is low, and the cost is low, which is suitable for industrial production and application.

Description

Visible light responsive photocatalyst Li2GaB3O7 and its preparation method

technical field

The invention relates to a photocatalyst Li ₂ GaB ₃ O ₇ responding to visible light and a preparation method thereof, belonging to the field of inorganic photocatalytic materials.

Background technique

With the development of society and economy, people pay more and more attention to energy and ecological environment. Solving the problems of energy shortage and environmental pollution is an urgent need to achieve sustainable development, improve people's quality of life and ensure national security.

Since the late 1970s, people have proposed the use of photocatalysts to decompose organic substances such as pesticides and odorous substances in water and the atmosphere, and self-cleaning of solid surfaces coated with photocatalysts. The principle of photocatalytic reaction is that after the photocatalyst absorbs photons higher than its bandgap energy, holes and electrons are generated, and these holes and electrons undergo oxidation and reduction reactions respectively to decompose harmful chemicals and organic biomass. and sterilization purposes. There are many kinds of photocatalysts, the most representative of which is titanium dioxide (TiO ₂ ), which has been used to decompose organic substances such as pesticides and odorous substances in water and the atmosphere. The activity can only be shown under the irradiation of short ultraviolet rays, and it can only work indoors or in places with ultraviolet lamps, and can hardly use visible light, which greatly limits the use of titanium dioxide photocatalysts.

Considering the practicability of photocatalysts in decomposing harmful substances, utilizing sunlight as a light source is indispensable. Among the sunlight irradiated to the surface, the intensity of visible light with a wavelength near 500nm is the highest, and the energy in the visible light region with a wavelength of 400nm~750nm is about 43% of the total energy of sunlight. Therefore, in order to use it efficiently, the development and research of bismuth-based photocatalysts A series of significant results have been achieved, trivalent bismuth complexes such as BiVO ₄ , Bi ₂ MoO ₆ , Bi ₂ Mo ₂ O ₉ , Bi ₂ Mo ₃ O ₁₂ and Bi ₂ WO ₄ have been reported to have good properties under visible light. absorb. A series of niobium (tantalum) salt photocatalysts have been widely studied due to their high photocatalytic activity. For example, niobate photocatalysts Pb ₃ Nb ₄ O ₁₃ , BiNbO ₄ and Bi ₂ MNbO ₇ (M=Al, Ga, In, Y, rare earth elements and Fe) etc. and niobium potassium composite oxide photocatalysts such as KNbO ₃ , KNb ₃ O ₈ , K ₄ Nb ₆ O ₁₇ and K ₆ Nb _10.6 O ₃₀ all have good photocatalytic properties, but their intrinsic photocatalytic effect is weak or inactive in the visible light range.

Although photocatalysis research has been carried out for several years, the types of photocatalysts with visible light response reported are still very limited, and there are still problems such as low photoconversion efficiency, poor stability and narrow spectral response range, so the research and development of new photocatalysts with Efficient photocatalysts responsive to visible light are highly desirable. We have studied the photocatalytic properties of compounds composed of Li ₂ GaB ₃ O ₇ , Li ₂ AlB ₃ O ₇ , and Li ₂ InB ₃ O ₇ , and found that Li ₂ GaB ₃ O ₇ is a semiconductor with a band gap of 2.68eV, It has excellent photocatalytic performance of visible light response; while other samples are insulators with a band gap width greater than 3.2eV, and cannot show activity under ultraviolet irradiation.

Contents of the invention

The object of the present invention is to provide a photocatalyst Li ₂ GaB ₃ O ₇ with visible light response and a preparation method thereof.

The chemical composition formula of the photocatalyst with visible light response involved in the present invention is: Li ₂ GaB ₃ O ₇ .

The specific steps of the preparation method of the above-mentioned visible light-responsive photocatalyst are:

(1) The raw powders of 99.9% analytically pure chemical raw materials Li ₂ CO ₃ , Ga ₂ O ₃ and H ₃ BO ₃ are weighed and prepared according to the composition of Li ₂ GaB ₃ O ₇ .

(2) Mix the raw materials prepared in step (1), put them into a ball mill jar, add zirconia balls and absolute ethanol, ball mill for 8 hours, mix and grind until fine, take it out and dry it, and pass through a 200-mesh sieve.

(3) Pre-fire the uniformly mixed powder in step (2) at 700~750°C, keep it warm for 6 hours, cool it down to room temperature naturally, and then pulverize it through a ball mill to make the average particle diameter smaller than 2 μm, and then Li ₂ GaB ₃ O ₇ powder.

The photocatalyst obtained by the present invention has a wide spectral response range, high photoconversion efficiency and good stability, and has the functions of decomposing harmful chemical substances, organic biomass and sterilizing under visible light irradiation; in addition, the preparation method is simple, the synthesis temperature is low, and the cost is low , suitable for industrial production and application.

Detailed ways

The present invention will be described in detail below:

1. In order to obtain the composite oxide used in the present invention, first use solid-phase synthesis to prepare powder, that is, mix various oxides or carbonates as raw materials according to the stoichiometric ratio of the target composition, and then mix them under normal pressure Synthesized in air atmosphere.

2. In order to effectively utilize light, the size of the photocatalyst in the present invention is preferably at the micron level, or even nanoparticles, and has a larger specific surface area. The oxide powder prepared by solid phase synthesis has larger particles and smaller surface area, but the particle diameter can be reduced by ball mill pulverization.

3. In the photocatalytic experiment of the present invention, methyl orange is used as a simulated organic pollutant, and its concentration is 20 mg/L; the amount of photocatalyst Li ₂ GaB ₃ O ₇ added is 1 g/L; the light source uses a 300W xenon lamp, and the reaction tank uses The vessel made of borosilicate glass was filtered to obtain light with a wavelength greater than 420nm, and then irradiated with the photocatalyst; the catalytic time was set to 60 minutes.

Example 1:

(1) The raw powders of 99.9% analytically pure chemical raw materials Li ₂ CO ₃ , Ga ₂ O ₃ and H ₃ BO ₃ are weighed and prepared according to the composition of Li ₂ GaB ₃ O ₇ .

(2) Mix the raw materials prepared in step (1), put them into a ball mill jar, add zirconia balls and absolute ethanol, ball mill for 8 hours, mix and grind until fine, take it out and dry it, and pass through a 200-mesh sieve.

(3) Pre-fire the uniformly mixed powder in step (2) at 700°C, keep it warm for 6 hours, cool it down to room temperature naturally, and then pulverize it with a ball mill to make the average particle diameter smaller than 2 μm, that is, Li ₂ GaB ₃ O ₇ powder.

The prepared photocatalyst can remove 97.1% of methyl orange in 60 minutes under the irradiation of visible light with a wavelength greater than 420nm.

Example 2:

(1) The raw powders of 99.9% analytically pure chemical raw materials Li ₂ CO ₃ , Ga ₂ O ₃ and H ₃ BO ₃ are weighed and prepared according to the composition of Li ₂ GaB ₃ O ₇ .

(2) Mix the raw materials prepared in step (1), put them into a ball mill jar, add zirconia balls and absolute ethanol, ball mill for 8 hours, mix and grind until fine, take it out and dry it, and pass through a 200-mesh sieve.

(3) Pre-fire the uniformly mixed powder in step (2) at 730°C, keep it warm for 6 hours, cool it down to room temperature naturally, and then pulverize it with a ball mill to make the average particle diameter smaller than 2 μm, that is, Li ₂ GaB ₃ O ₇ powder.

The prepared photocatalyst can remove 98.7% of methyl orange in 60 minutes under the irradiation of visible light with a wavelength greater than 420nm.

Example 3:

(1) The raw powders of 99.9% analytically pure chemical raw materials Li ₂ CO ₃ , Ga ₂ O ₃ and H ₃ BO ₃ are weighed and prepared according to the composition of Li ₂ GaB ₃ O ₇ .

(2) Mix the raw materials prepared in step (1), put them into a ball mill jar, add zirconia balls and absolute ethanol, ball mill for 8 hours, mix and grind until fine, take it out and dry it, and pass through a 200-mesh sieve.

(3) Pre-fire the uniformly mixed powder in step (2) at 750°C, keep it warm for 6 hours, cool it down to room temperature naturally, and then pulverize it with a ball mill to make the average particle diameter smaller than 2 μm, that is, Li ₂ GaB ₃ O ₇ powder.

The prepared photocatalyst can remove 97.9% of methyl orange in 60 minutes under the irradiation of visible light with wavelength greater than 420nm.

The present invention is by no means limited to the above examples. The upper and lower limits and interval values of each temperature can realize the present invention, and the embodiments are not listed one by one here.

The photocatalyst powder prepared in the above invention examples can be loaded on the surface of various substrates. The substrate can be glass, ceramics, activated carbon or quartz sand, etc., and the photocatalyst can be loaded on the surface of the substrate in the form of a thin film.

Claims (1)

1. A photocatalyst responding to visible light, characterized in that the chemical composition formula of the photocatalyst is Li ₂ GaB ₃ O ₇ ; The specific steps of the preparation method of the photocatalyst are: (1) Weigh the original powders of 99.9% analytically pure chemical raw materials Li ₂ CO ₃ , Ga ₂ O ₃ and H ₃ BO ₃ according to the composition of Li ₂ GaB ₃ O ₇ ; (2) Mix the raw materials prepared in step (1), put them into a ball mill tank, add zirconia balls and absolute ethanol, ball mill for 8 hours, mix and grind, take out and dry, and pass through a 200-mesh sieve; (3) Pre-fire the uniformly mixed powder in step (2) at 700~750°C, keep it warm for 6 hours, cool it down to room temperature naturally, and then pulverize it with a ball mill so that the average particle diameter is less than 2 μm to obtain Li ₂ GaB ₃ O ₇ powder.