CN104353477A - P-n heterojunction type visible light catalyst B4C/TiO2 and preparation method thereof - Google Patents

Abstract

The invention discloses a p-n heterojunction type visible light catalyst B4C/TiO2 and a preparation method thereof. The p-n heterojunction type visible light catalyst B4C/TiO2 is composed of B4C and TiO2, wherein the mass ratio of the B4C to the TiO2 ranges from 1:21 to 1:2. The preparation method of the p-n heterojunction type visible light catalyst B4C/TiO2 comprises the following steps: (a) purifying commercially available B4C; (b) preparing B4C/TiO2 by the purified commercially available B4C and tetrabutyl titanate under a hydrothermal condition, wherein the mass ratio of the B4C to the TiO2 ranges from 1:21 to 1:2 based on the calculating ratio that 1 mol of tetrabutyl titanate generates 1 mol of TiO2; and (c) washing a product prepared by the step (b) and separating to obtain the B4C/TiO2; and drying and milling for later use. According to the p-n heterojunction type visible light catalyst B4C/TiO2 and the preparation method thereof, the solar energy utilization efficiency of a wide band gap n-type semiconductor TiO2 can be improved and the compounding of electrons generated by laser and holes is inhibited; the raw materials are cheap and easily available; and the preparation process is simple and convenient and the repeatability is good, and the p-n heterojunction type visible light catalyst B4C/TiO2 can be prepared in a large scale and has a good commercialized application prospect.

Description

A kind of p-n heterojunction type visible light catalyst B 4c/TiO 2and preparation method thereof

Technical field

The present invention relates to and belong to new energy materials preparation and photochemical catalyst art field, particularly a kind of p-n heterojunction type visible light catalyst B ₄c/TiO ₂and preparation method thereof.

Background technology

Along with resource exhaustion, environment worsen and the enhancing of common people's environmental consciousness, energy shortage and problem of environmental pollution attract people's attention day by day.Because solar energy photocatalytic clean technologies are expected to the difficult problem solving above-mentioned restriction economy, social development, it has become various countries' competitively study hotspot.

Although solar energy photocatalytic research achieves notable results, face some problem demanding prompt solutions at present, as low in sun utilization ratio, the easy inactivation of catalyst, the easy compound of photogenerated charge etc., strongly limit photocatalysis technology industrialization.Such as, TiO ₂the Wuli-Shili-Renli system approach good because of it and become the preferred material of photocatalysis research, but uses pure TiO ₂as catalyst, the easy compound of electronics and hole that optical excitation produces; Again because its forbidden band is wider, visible ray (accounting for greatly 40% of solar spectrum) can not be absorbed, the problem such as which results in the broad stopband n-type semiconductor electronics that low and optical excitation produces to Solar use efficiency and hole utilization ratio is low.

Although B at present ₄c has been widely used in the fields such as chemical industry, pottery, nuclear power, national defence, military project, but less as the research of photochemical catalyst.In addition, because preparation method limit, B commercially available at present ₄c specific area is less, is unfavorable for improving photocatalysis performance.

Summary of the invention

In view of this, the invention reside in and provide one can improve broad stopband n-type semiconductor TiO ₂solar use efficiency, the electronics suppressing optical excitation to produce and the p-n heterojunction type visible light catalyst B of hole-recombination ₄c/TiO ₂, this p-n heterojunction type visible light catalyst B is provided simultaneously ₄c/TiO ₂preparation method.

The present invention adopts following technical scheme to realize: a kind of p-n heterojunction type visible light catalyst B ₄c/TiO ₂, by B ₄c and TiO ₂composition, described B ₄c and described TiO ₂mass ratio be 1:21 ~ 1:2.

Above-mentioned p-n heterojunction type visible light catalyst B ₄c/TiO ₂, described B ₄c and described TiO ₂mass ratio be 1:6.

Above-mentioned p-n heterojunction type visible light catalyst B ₄c/TiO ₂preparation method, comprise the steps:

The commercially available B of (a) purifying ₄c;

B () is with the commercially available B after purifying ₄c and butyl titanate prepare B under hydrothermal conditions ₄c/TiO ₂, generate 1mol TiO according to 1mol butyl titanate ₂calculate, B ₄c and TiO ₂mass ratio be 1:21 ~ 1:2;

C product that step (b) prepares by () washs, and is separated to obtain B ₄c/TiO ₂, then dry, grind, sieve for subsequent use.

Above-mentioned p-n heterojunction type visible light catalyst B ₄c/TiO ₂preparation method, step (a) comprises the steps:

(1) by commercially available B ₄c adds in hydrochloric acid, and ultrasonic disperse 20 ~ 40min, then stirs 4 ~ 8h;

(2) step (1) is prepared product use deionized water and absolute ethanol washing 3 ~ 5 times respectively;

(3) by the product vacuum drying 10 ~ 16h at 80 ~ 100 DEG C after washing, then grind, sieve, obtain the commercially available B after purifying ₄c.

Above-mentioned p-n heterojunction type visible light catalyst B ₄c/TiO ₂preparation method, used salt acid concentration is 1 ~ 3mol/L in described step (1).

Above-mentioned p-n heterojunction type visible light catalyst B ₄c/TiO ₂preparation method, described step (b) comprises the steps:

I () is by the commercially available B after purifying ₄c adds in butyl titanate, and ultrasonic disperse 8 ~ 12min, then stirs 0.5 ~ 2h, can by B ₄the suspension of C and butyl titanate composition; With B ₄c and butyl titanate are as presoma;

(ii) using hydrofluoric acid as adjuvant and structure directing agent, hydrofluoric acid solution is added in step (i) gained suspension, and gained mixture is transferred to is equipped with in teflon-lined reactor, reaction temperature is 150 ~ 210 DEG C, and the reaction time is 20 ~ 28h.

Above-mentioned p-n heterojunction type visible light catalyst B ₄c/TiO ₂preparation method, the hydrofluoric acid concentration in step (ii) in hydrofluoric acid solution used is 40wt%; In step (ii), the volume of hydrofluoric acid solution used and the volume ratio of described butyl titanate are 3:26.5.

Above-mentioned p-n heterojunction type visible light catalyst B ₄c/TiO ₂preparation method, step (c) comprises the steps:

(I), after reaction terminates, the product that step (ii) prepares is naturally cooled to room temperature, then washs more than 3 times or 3 times by absolute ethyl alcohol and deionized water respectively, be then separated;

(II) the product vacuum drying 10 ~ 14h at 80 ~ 100 DEG C step (I) prepared, then grinds, sieves for subsequent use.

Above-mentioned p-n heterojunction type visible light catalyst B ₄c/TiO ₂preparation method, comprise the steps:

A () is by 1 gram of commercially available B ₄c adds in the hydrochloric acid of 60mL 2mol/L, ultrasonic disperse 30min, stirs 6h, is then separated, and products therefrom is used respectively deionized water and absolute ethanol washing 3 times, then by the product vacuum drying 12h at 80 ~ 100 DEG C after washing, obtains the commercially available B after purifying ₄c, then by the commercially available B after purifying ₄c grinds, sieves for subsequent use;

Commercially available B after b purifying that step (a) prepares by () ₄c joins in 26.5mL butyl titanate, stirs 1h and obtain by B after ultrasonic disperse 10min ₄the suspension of C and butyl titanate composition, then in gained suspension, the hydrofluoric acid solution that 3mL concentration is 40wt% is added, and gained mixture is transferred to is equipped with in teflon-lined reactor, at 180 DEG C, react 12h, then naturally cool to room temperature;

C product that step (b) prepares by () is separated with after deionized water and absolute ethanol washing 3 times respectively, by products therefrom vacuum drying 12h at 100 DEG C, then by dried product grinding, sieve for subsequent use.

The invention has the beneficial effects as follows:

1. p-n heterojunction type visible light catalyst B of the present invention ₄c/TiO ₂overcome B preferably ₄c and TiO ₂shortcoming, significantly improve the utilization ratio of solar energy, the electronics that can effectively suppress optical excitation to produce and hole-recombination, present excellent visible light catalytic reduction CO ₂methane performance processed.

2. adopt the p-n heterojunction type visible light catalyst B that preparation method of the present invention prepares ₄c/TiO ₂microcosmic is the nanometer sheet of length and width about 80 ~ 100nm, thick about 10nm, pattern rule, has stronger light absorpting ability in whole visible region, and has larger specific area.

3. the present invention not only cheaper starting materials be easy to get, preparation process is simple and convenient, reproducible, and be applicable to scale preparation, there is good commercial applications prospect; There is certain universality, can be used for constructing B ₄the p-n heterojunction type composite nano materials of C base is to solve broad stopband n-type semiconductor (as ZnO, SrTiO ₃, Ta ₂o ₅deng) difficult problem of the easy compound of electronics and hole that produces of the low and optical excitation of the Solar use efficiency that faces.

Accompanying drawing explanation

Fig. 1 is B ₄c, TiO ₂, and B ₄c and TiO ₂the B for preparing when being and being respectively 1:3,1:6 and 1:21 of mass ratio ₄c/TiO ₂xRD collection of illustrative plates;

Fig. 2 a is TiO ₂tEM photo;

Fig. 2 b is B ₄c and TiO ₂the B obtained when being 1:6 of mass ratio ₄c/TiO ₂tEM photo;

Fig. 3 is TiO ₂, B ₄c, and B ₄c and TiO ₂the B that mass ratio prepares when being respectively 1:3,1:6 and 1:21 ₄c/TiO ₂uV-Vis DRS collection of illustrative plates;

Fig. 4 is TiO ₂, B ₄c, and B ₄c and TiO ₂the B that mass ratio prepares when being respectively 1:3,1:6 and 1:21 ₄c/TiO ₂for visible light catalytic reduction CO ₂synthesis CH ₄performance comparison figure.

In Fig. 1 to Fig. 4:

B used ₄c is that embodiment 2 prepares, TiO used ₂for embodiment 3 prepares.

Prepared B ₄c/TiO ₂sample, B ₄c and TiO ₂mass ratio be 1:3,1:6 and 1:21, be abbreviated as B respectively ₄c/TiO ₂(1/3), B ₄c/TiO ₂(1/6), B ₄c/TiO ₂(1/21).

Detailed description of the invention

For clearly demonstrating the scheme in the present invention, providing preferred embodiment below and being described with reference to the accompanying drawings.

Embodiment 1

Prepare p-n heterojunction type visible light catalyst B in accordance with the following steps ₄c/TiO ₂:

The commercially available B of (a) purifying ₄c

Due to commercially available B ₄c contains boron oxide compound and transition metal oxide etc., is using it for preparation B ₄c/TiO ₂time, in order to avoid commercially available B ₄in C, the contained impurity such as boron oxide compound and transition metal oxide is to B ₄c/TiO ₂have a negative impact, need commercially available B ₄c carries out purification process.

Get 1 gram of commercially available B ₄c adds in the hydrochloric acid of 60mL 2mol/L, ultrasonic disperse 30min, then 6h is stirred, after stirring terminates, gained mixture is carried out Separation of Solid and Liquid, and the solid product be isolated to is used respectively deionized water and absolute ethanol washing 3 times, then vacuum drying 12h at 80 DEG C, obtains the commercially available B after purifying ₄c, finally by the commercially available B after purifying ₄c grinds, sieves for subsequent use;

B () prepares B ₄c/TiO ₂

Commercially available B after the purifying that step (a) is prepared ₄c adds and fills 26.5mL butyl titanate [in the present invention, in all embodiments, the density of butyl titanate used is 0.966g/mL, generates 1mol TiO according to 1mol butyl titanate ₂calculate ,] container in, ultrasonic disperse 10min, and then stir 1h, makes described B ₄c is dispersed in described butyl titanate and is formed by B ₄the suspension that C and butyl titanate form, then in described suspension, add 3mL hydrofluoric acid solution, then gained mixture is transferred to and is equipped with in teflon-lined reactor, react at 180 DEG C, reaction time is 12h, then naturally cools to room temperature.

The post processing of c product that () step (b) prepares

Product step (b) prepared first spends deionized water 3 times, and then with absolute ethanol washing 3 times, carry out Separation of Solid and Liquid, and gained solid product is put into vacuum drying chamber, namely 100 DEG C of vacuum drying 12h obtain p-n heterojunction type visible light catalyst B ₄c/TiO ₂, by dried B ₄c/TiO ₂grind, sieve for subsequent use.

Embodiment 2

According to the commercially available B after the obtained purifying of step (a) in embodiment 1 ₄c.

Embodiment 3

Preparation TiO ₂, the steps include:

B () by 26.5mL butyl titanate ultrasonic disperse 10min, and then stirs 1h, then add 3mL hydrofluoric acid solution, then being transferred to by gained mixture is equipped with in teflon-lined reactor, react at 180 DEG C, the reaction time is 12h, then naturally cools to room temperature.

C product that step (b) prepares by () first spends deionized water 3 times, and then with absolute ethanol washing 3 times, carry out Separation of Solid and Liquid, and gained solid product is put into vacuum drying chamber, namely 100 DEG C of vacuum drying 12h obtain TiO ₂, by dried TiO ₂grind, sieve for subsequent use.

TiO in the present embodiment ₂preparation and embodiment 1 in B ₄c/TiO ₂preparation difference be only not add B in preparation process ₄c.

Embodiment 4

According to the p-n heterojunction type visible light catalyst B described in embodiment 1 ₄c/TiO ₂preparation method prepares p-n heterojunction type visible light catalyst B ₄c/TiO ₂:

The commercially available B of (a) purifying ₄c

Get 1 gram of commercially available B ₄c adds in the hydrochloric acid of 60mL 3mol/L, stir 4h after ultrasonic disperse 40min, stir after terminating and gained mixture is carried out Separation of Solid and Liquid, and the solid product be isolated to is used respectively deionized water and absolute ethanol washing 3 times, then vacuum drying 10h at 80 DEG C, obtains the commercially available B after purifying ₄c, finally by the commercially available B after purifying ₄c grinds, sieves for subsequent use;

B () prepares B ₄c/TiO ₂

Commercially available B after the purifying that step (a) is prepared ₄c adds in the container filling 13.25mL butyl titanate, ultrasonic disperse 8min, and then stirs 1.5h, makes described B ₄c is dispersed in described butyl titanate and is formed by B ₄the suspension of C and butyl titanate composition, then in described suspension, add 1.5mL 40wt% hydrofluoric acid solution, then gained mixture is transferred to and is equipped with in teflon-lined reactor, react at 200 DEG C, reaction time is 20h, then naturally cools to room temperature.

Then according to step (c) described in embodiment 1, subsequent treatment is carried out to step (b) products therefrom in the present embodiment.

Embodiment 5

According to the p-n heterojunction type visible light catalyst B described in embodiment 1 ₄c/TiO ₂preparation method prepares the present embodiment B used ₄c/TiO ₂, its difference is: in step (b), the consumption of butyl titanate used and hydrofluoric acid solution is different, and B ₄c and butyl titanate in a kettle. the reaction time different.In the present embodiment, the amount of butyl titanate used is 92.6mL, and described hydrofluoric acid consumption is 10.5mL, B ₄c and the butyl titanate reaction time is in a kettle. 26h.

the performance test of products therefrom and interpretation of result in embodiment 1 to embodiment 5

One, the XRD collection of illustrative plates of products therefrom in embodiment 1 to embodiment 5.

Fig. 1 is the XRD collection of illustrative plates of products therefrom in embodiment 1 to embodiment 5, shows that sample has good degree of crystallinity; Due to B ₄less or the peak position of the content of C and TiO ₂coincidence, B ₄c characteristic diffraction peak intensity is more weak, therefore at B ₄c/TiO ₂in sample XRD collection of illustrative plates, only observe the characteristic diffraction peak of (012), (104) and (201) crystal face, and peak is by force along with B ₄c content increases and strengthens.

Two, the TEM photo of products therefrom in embodiment 1 and embodiment 3.

Fig. 2 b embodiment 1 gained B ₄c/TiO ₂tEM photo, show that sample is the sheet of regular shape, length and width are about 80 ~ 100nm, and thickness is about 10nm.

Fig. 2 a embodiment 3 gained TiO ₂tEM photo.

Three, the UV-Vis DRS collection of illustrative plates of products therefrom in embodiment 1 to embodiment 5

Fig. 3 is the UV-Vis DRS collection of illustrative plates of products therefrom in embodiment 1 to embodiment 5, shows that sample has at visible region (wavelength is between 400 ~ 800nm) and absorbs more by force; Along with B ₄c content increases, and absorbs visible ray ability and strengthens.

Four, in embodiment 1 to embodiment 5, products therefrom is used for visible light catalytic reduction CO ₂synthesis CH ₄.

With H ₂for electron donor and hydrogen source, visible light catalytic reduction CO ₂, comprise the steps:

Light source is 300W xenon lamp, is equipped with ultraviolet/infrared fileter (light of wavelength between 405 ~ 723nm can pass through).React a volume be 200mL have dismountable Pyrex quartz plane window (effective illuminating area is about 20cm ²) container in carry out, irradiate from top.When Kaolinite Preparation of Catalyst film, by 10mg catalyst deposit at Pyrex quartz plane window, heating, drying, vacuum drying 12h under 363K.Before introducing unstripped gas, reactor is evacuated to about 10Pa and keeps 20min.Utilize mass-flow gas meter to control and regulate the concentration of unstripped gas and Balance Air, H ₂and CO ₂concentration be respectively 4vol% and 1vol%, argon gas is as Balance Air.

Methane content in reaction gas-phase product SRI-8610C gas-chromatography (being equipped with PorapakQ chromatographic column, methanator, flame ionization ditector and six-way valve injector) measures, and carrier gas is argon gas, quantified by external standard method.At interval of certain hour, auto injection, each gas phase sampling quantity is 0.5mL.

Fig. 4 is that in embodiment 1 to embodiment 5, products therefrom carries out visible light catalytic reduction CO ₂the performance comparison figure of synthesizing methane.Result shows, under other experimental condition same case, with pure B ₄c or TiO ₂compare, B ₄c/TiO ₂visible light catalytic reducing carbon dioxide methane performance significantly improves.B ₄c content is to B ₄c/TiO ₂catalytic performance has remarkable impact, B ₄c and TiO ₂quality proportioning when being 1:3, the methane of every gram of catalyst generation per hour 31.7ppm; B ₄c and TiO ₂quality proportioning when being 1:21, the methane of every gram of catalyst generation per hour 37.4ppm; B ₄c and TiO ₂best in quality proportioning be 1:6, the methane of now every gram of catalyst generation per hour 49.1ppm; This is the result of the many factors comprehensive functions such as catalyst visible absorption ability, catalyst surface area and photogenerated charge separative efficiency.

Specific surface area analysis shows: along with B ₄c content increases, B ₄c/TiO ₂specific area reduces, and works as B ₄c and TiO ₂mass ratio when increasing to 1/2 by 1/21, B ₄c/TiO ₂specific area is by 80.8m ²/ g is reduced to 32.6m ²/ g; And B ₄c specific area is only 1.6m ²/ g.Obviously, with TiO ₂after coupling, composite specific area enlarges markedly, and is conducive to the photocatalysis performance improving material.

Above-described embodiment is only for the invention example is clearly described, and the restriction not to the invention detailed description of the invention.For those of ordinary skill in the field, can also make other changes in different forms on the basis of the above description.Here exhaustive without the need to also giving all embodiments.All within the spirit and principles in the present invention any apparent change of extending out or variation be still among the protection domain of the invention claim.

Claims (9)

1. a p-n heterojunction type visible light catalyst B ₄c/TiO ₂, it is characterized in that, by B ₄c and TiO ₂composition, described B ₄c and described TiO ₂mass ratio be 1:21 ~ 1:2.

2. p-n heterojunction type visible light catalyst B according to claim 1 ₄c/TiO ₂, it is characterized in that, described B ₄c and described TiO ₂mass ratio be 1:6.

3.p-n heterojunction type visible light catalyst B ₄c/TiO ₂preparation method, it is characterized in that, comprise the steps:

The commercially available B of (a) purifying ₄c;

B () is with the commercially available B after purifying ₄c and butyl titanate prepare B under hydrothermal conditions ₄c/TiO ₂, generate 1mol TiO according to 1mol butyl titanate ₂calculate, B ₄c and TiO ₂mass ratio be 1:21 ~ 1:2;

C product that step (b) prepares by () washs, and is separated to obtain B ₄c/TiO ₂, then dry, grind, sieve for subsequent use.

4. p-n heterojunction type visible light catalyst B according to claim 3 ₄c/TiO ₂preparation method, it is characterized in that, step (a) comprises the steps:

(1) by commercially available B ₄c adds in hydrochloric acid, and ultrasonic disperse 20 ~ 40min, then stirs 4 ~ 8h;

(2) product that step (1) prepares is used respectively deionized water and absolute ethanol washing 3 ~ 5 times;

(3) by the product vacuum drying 10 ~ 16h at 80 ~ 100 DEG C after washing, then grind, sieve, obtain the commercially available B after purifying ₄c.

5. p-n heterojunction type visible light catalyst B according to claim 4 ₄c/TiO ₂preparation method, it is characterized in that, used salt acid concentration is 1 ~ 3mol/L in described step (1).

6. p-n heterojunction type visible light catalyst B according to claim 3 ₄c/TiO ₂preparation method, it is characterized in that, described step (b) comprises the steps:

I () is by the commercially available B after purifying ₄c adds in butyl titanate, and ultrasonic disperse 8 ~ 12min, then stirs 0.5 ~ 2h, can by B ₄the suspension of C and butyl titanate composition; With B ₄c and butyl titanate are as presoma;

(ii) using hydrofluoric acid as adjuvant and structure directing agent, hydrofluoric acid solution is added in step (i) gained suspension, and gained mixture is transferred to is equipped with in teflon-lined reactor, reaction temperature is 150 ~ 210 DEG C, and the reaction time is 20 ~ 28h.

7. p-n heterojunction type visible light catalyst B according to claim 6 ₄c/TiO ₂preparation method, it is characterized in that, the hydrofluoric acid concentration in step (ii) in hydrofluoric acid solution used is 40wt%; In step (ii), the volume of hydrofluoric acid solution used and the volume ratio of described butyl titanate are 3:26.5.

8. p-n heterojunction type visible light catalyst B according to claim 6 ₄c/TiO ₂preparation method, it is characterized in that, step (c) comprises the steps:

(I), after reaction terminates, the product that step (ii) prepares is naturally cooled to room temperature, then washs more than 3 times or 3 times by absolute ethyl alcohol and deionized water respectively, be then separated;

(II) the product vacuum drying 10 ~ 14h at 80 ~ 100 DEG C step (I) prepared, then grinds, sieves for subsequent use.

9. according to the arbitrary described p-n heterojunction type visible light catalyst B of claim 3 ~ 8 ₄c/TiO ₂preparation method, it is characterized in that, comprise the steps:

A () is by 1 gram of commercially available B ₄c adds in the hydrochloric acid of 60mL 2mol/L, ultrasonic disperse 30min, stirs 6h, is then separated, and products therefrom is used respectively deionized water and absolute ethanol washing 3 times, then by the product vacuum drying 12h at 80 ~ 100 DEG C after washing, obtains the commercially available B after purifying ₄c, then by the commercially available B after purifying ₄c grinds, sieves for subsequent use;

Commercially available B after b purifying that step (a) prepares by () ₄c joins in 26.5mL butyl titanate, stirs 1h and obtain by B after ultrasonic disperse 10min ₄the suspension of C and butyl titanate composition, then in gained suspension, the hydrofluoric acid solution that 3mL concentration is 40wt% is added, and gained mixture is transferred to is equipped with in teflon-lined reactor, at 180 DEG C, react 12h, then naturally cool to room temperature;

C product that step (b) prepares by () is separated with after deionized water and absolute ethanol washing 3 times respectively, by products therefrom vacuum drying 12h at 100 DEG C, then by dried product grinding, sieve for subsequent use.