AU2021106790A4

AU2021106790A4 - BiVO4/PROTONATED g-C3N4/AgI TERNARY COMPOSITE PHOTOCATALYST AND PREPARATION METHOD THEREOF

Info

Publication number: AU2021106790A4
Application number: AU2021106790A
Authority: AU
Inventors: Bo Liang; Chaoyang SUN; Min Xu; Jingkai YANG; Hongli Zhao
Original assignee: Yanshan University
Current assignee: Yanshan University
Priority date: 2021-08-24
Filing date: 2021-08-24
Publication date: 2021-11-18
Anticipated expiration: 2029-08-24

Abstract

: A BiVO 4/protonated g-C3N4/AgI ternary composite photocatalyst and a preparation method thereof are disclosed. First, BiVO 4 and protonated g-C3N4 are respectively prepared by a hydrothermal process and a calcination process. BiVO4/protonated g-C3N4 composite is prepared by an electrostatic self-assembly process. The BiVO4/protonated g-C3N4/AgI ternary composite photocatalyst is then prepared by an in-situ precipitation process. The ternary composite photocatalyst prepared in the present disclosure could quickly separate photo-generated electrons and holes, increase the life of charge carrier, reduce the recombination ratio of charge carrier, and have a extended response to visible light. After being catalyzed for 60 min, the degradation ratio of the rhodamine B solution could reach 94.7%. The composite photocatalyst could be used to degrade organic dyes under visible light, which is of great significance to environmental governance. Figure 3 for publication -2/2 1.0 0.8 -+-BiVO/AgI -. - BiVO/pCN/AgI 0.0~ 10 20 30 40 50 60 Degradation time (min) FIG.3 2

Description

-2/2

1.0

0.8

-+-BiVO/AgI -. - BiVO/pCN/AgI 0.0~ 10 20 30 40 50 60 Degradation time (min)

FIG.3

BiVO4/PROTONATED g-C3N4/AgI TERNARY COMPOSITE

PHOTOCATALYST AND PREPARATION METHOD THEREOF TECHNICAL FIELD

[01] The present disclosure relates to the technical field of photocatalysts, and in particular to a BiVO4/protonated g-C3N4/AgI ternary composite photocatalyst and a

preparation method thereof.

DEFINITION

[02] In the present description and claims, the term "comprising" shall be

understood to have a broad meaning similar to the term "including" and will be

understood to imply the inclusion of a stated integer or step or group of integers or steps

but not the exclusion of any other integer or step or group of integers or steps. This

definition also applies to variations on the term "comprising" such as "comprise" and

"comprises".

BACKGROUNDART

[03] The photocatalytic technology with semiconductor oxide as the main body has

become a relatively effective technology for the treatment of environmental pollutants

due to its excellent characteristics such as no pollution, simple completion process,

ability to directly use solar energy as a reaction light source and the generation of clean

energy. BiVO4 , as a new type of semiconductor material, has a narrow band gap (about

2.40 eV), excellent visible light response, suitable conduction band and valence band

positions (vs standard hydrogen electrodes), and is an effective semiconductor

photocatalyst that meanwhile has the ability to evolve oxygen via water splitting, reduce

and degrade pollutants. However, the characteristics of poor charge transport ability, fast

recombination and poor adsorption are the obstacles to achieve a satisfactory

photocatalytic activity for BiVO4 .It is considered to be an effective strategy to construct

an appropriate heterojunction photocatalytic system from BiVO 4 and other semiconductors, to further enhance the photocatalytic activity. In addition, studies have proven that the preparation of suitable ternary heterojunction is more advantageous to enhance the visible light response capability and the separation of charge carriers, thereby achieving a higher photocatalytic activity.

[04] Two-dimensional materials (2D) possess various excellent properties, such as high charge mobility and tunable electronic properties. In recent years, as a new

member of the 2D family, graphitic carbon nitride (g-C3N4) has received great attention

for its highly delocalized conjugated system, high chemical stability, and low cost of

mass production. For example, Xiao et al. prepared W3/g-C3N4 through precisely

controlled in situ hydrolysis and a polymerization process consecutively. The synergistic

effect between W03 and g-C3N4 could improve the interface charge transfer efficiency

and the number of redox active sites, resulting in the superior photocatalytic

performance (Appl. Catal. B. 220 (2018) 417-428). In addition, the researchers also

studied the BiVO 4 modified with g-C3N4. Wang et al. prepared BiVO 4/g-C3N 4

photocatalyst by ultrasonic dispersion method, which exhibited excellent photocatalytic

degradation activity for rhodamine B in sewage (Appl. Catal. B. 234 (2018) 37-49).

Also, silver iodide (AgI) with superior redox ability has been widely used in the field of

photocatalysis. However, AgI presents irregular spherical particles and is easy to

agglomerate, thus inhibiting them to be high-performance photocatalysts. Coupling AgI

with other stable semiconductor to form heterojunction should be a good solution to the

problem. Chen et al. verified that the heterostructure in the BiVO 4 /AgI photocatalyst

system could promote photogenerated electrons transfer and improve photocatalytic

activity (ACSAppl. Mater. Inter. 8 (2016) 32887-32900).

[05] According to previous research, BiVO 4 /g-C3N 4 and BiVO 4/AgI composite

demonstrated considerable enhancement of photocatalytic activity. In particular, g-C3N4

and AgI exhibit strong reduction ability, while BiVO 4 exhibits strong oxidiation ability,

and their energy band structures could match. Considering the advantages of g-C3N4

and AgI, their use to co-modify BiVO 4 may be an effective strategy for designing a

highly active photocatalyst. And so far, there is no research or public reports on the composite photocatalyst constructed by BiVO 4 , g-C3N4 and AgI. Therefore, to enhance the photocatalytic degradation of organic dyes under visible light, we have prepared a BiVO4/protonated g-C3N4/AgI ternary composite photocatalyst.

[06] The reference to prior art in the background above is not and should not be taken as an acknowledgment or any form of suggestion that the referenced prior art forms part of the common general knowledge in Australia or in any other country.

SUMMARY

[071 At least one embodiment of the present disclosure provides a heterojunction photocatalyst, which is capable of promoting efficient charge separation and exhibits high photocatalytic activity, and a preparation method thereof. The method has advantages of simple operation, short reaction time, and mild reaction conditions. The prepared BiVO4/protonated g-C3N4/AgI ternary composite photocatalyst exhibits high degradation activity under visible light irradiation, and has broad application prospects in environmental pollution control, energy and other fields.

[08] The present disclosure provides the following technical solutions:

[09] The present disclosure provides a BiVO4/protonated g-C3N4/AgI ternary composite photocatalyst, including BiVO4 , protonated g-C3N4, and AgI, wherein the composite photocatalyst is prepared by the steps of:

[10] (1) preparation of a BiVO 4 powder: dissolving Bi(N0 3 ) 3 -5H 2 0 in deionized

water, and fully stirring to form a solution A; dissolving NH 4VO 3 in deionized water, and fully stirring to form a solution B; pouring the solution B slowly into the solution A and stirring continuously to form a yellow mixture suspension, adjusting a pH value thereof to 7-9 by using ammonia water, and fully stirring to obtain a BiVO 4 precursor solution, pouring the BiVO 4 precursor solution into a hydrothermal reaction kettle with a filling degree of 70%, heating to a temperature of 180 °C, maintaining at the temperature and subjecting the resulting mixture to a reaction for 12 h, cooling the reaction kettle to room temperature, washing and drying to obtain the BiVO 4 powder;

[11] (2) preparation of a protonated g-C3N4 powder: placing melamine into a muffle furnace, heating to 550 °C at a heating rate of 4 °C/min and calcining at 550 °C for 4 h, cooling to room temperature, and grinding to obtain g-C3N4; dispersing the obtained g-C3N4 in 37% hydrochloric acid solution, sonicating the resulting mixture for min, then stirring for 60 min, washing and drying to obtain the protonated g-C3N4;

[12] (3) dissolving BiVO4 and the protonated g-C3N4 with a certain mass ratio in ethanol, sonicating the resulting mixture at room temperature and then stirring in a fume

hood for 24 h; after ethanol is volatilized, drying the resulting product at 60 °C for 12 h

to obtain a BiVO4/protonated g-C3N4 composite;

[13] (4) dissolving the BiVO4/protonated g-C3N4 composite in deionized water, sonicating the resulting mixture at room temperature for 10 min and then adding a

AgNO3 solution, stirring the resulting mixture for 1 h in the dark, adding a KI solution

dropwise during the stirring, stirring the resulting mixture for another 1 h, then washing

and drying to obtain the BiVO4/protonated g-C3N4/AgI ternary composite photocatalyst.

[14] In some embodiments, in step (1), a molar ratio of Bi(N 3 )3-5H 20 to NH4 VO 3

is 1 : 1.

[15] In some embodiments, in step (2), a dosage ratio of the g-C3N4 to the

hydrochloric acid solution is in the range of (1-4) g : (50-100) ml.

[16] In some embodiments, in step (3), a dosage ratio of BiVO 4 , the protonated

g-C3N4 and ethanol is in the range of (0.1-0.2) g : 0.1 g : 100 ml, and sonicating the

resulting mixture at room temperature is performed for 1-4 h.

[171 In some embodiments, in step (4), a dosage ratio of the BiVO4/protonated

g-C3N4 composite, deionized water, the AgNO3 solution, and the KI solution is 0.1 g :

ml : 0.0851 mmol : 0.0851 mmol, the AgNO3 solution has a AgNO3 concentration of

0.1 mol/L, and the KI solution has a KI concentration of 0.1 mol/L.

[18] In some embodiments, the present disclosure provides use of the

BiVO4/protonated g-C3N4/AgI ternary composite photocatalyst in the treatment of

organic dyes.

[19] The technical solutions of the present disclosure have the following technical

effects:

[201 1) The present disclosure makes it possible to successfully prepare a BiVO4/protonated g-C3N4/AgI ternary composite photocatalyst by electrostatic

self-assembly process and in-situ precipitation process for the first time. Compared with

pure BiVO 4 , the BiVO4/protonated g-C3N4/AgI ternary composite photocatalyst has a

higher photo-generated electron-hole separation effect and electron mobility, and thus it

shows more efficient photocatalytic activity.

[21] 2) The BiVO4/protonated g-C3N4/AgI ternary composite photocatalyst prepared in the present disclosure makes it possible to achieve high-efficiency

degradation of organic dyes under visible light, and the degradation rate of organic dyes

(rhodamine B) could be more than 94% within 60 min for illumination.

[22] 3) The method for preparing the BiVO4/protonated g-C3N4/AgI ternary composite photocatalyst according to the present disclosure is simple, easy to operate,

low in cost, and environmentally friendly.

BRIEF DESCRIPTION OF THE DRAWINGS

[23] FIG. 1 shows XRD patterns of BiVO 4 , protonated g-C3N4 (pCN), AgI, BiVO4/protonated g-C3N4, BiVO 4/AgI, and BiVO4/protonated g-C3N4/AgI ternary

composite photocatalyst as prepared in Example 1 of the present disclosure.

[24] FIG. 2 is a TEM image of the BiVO4/protonated g-C3N4/AgI ternary composite photocatalyst as prepared in Example 1 of the present disclosure.

[25] FIG. 3 is a diagram showing the degradation effect of rhodamine B catalyzed by

BiVO 4 , protonated g-C3N4 (pCN), AgI, BiVO 4/pCN, BiVO 4/AgI, and the

BiVO4/pCN/AgI ternary composite photocatalyst as prepared in Example 1 of the

present disclosure under visible light irradiation.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[26] Example 1

[27] (1) Preparation of a BiVO 4 Powder: 10 mmol of bismuth nitrate Bi(N0 3) 3 -5H 20

was weighed and dissolved in 40 ml of deionized water. The resulting mixture was stirred fully for 30 min, forming a solution A. 10 mmol of ammonium metavanadate NH 4VO 3 was weighed and dissolved in 40 ml of deionized water. The resulting mixture was stirred fully for 30 min, forming a solution B. The solution B was poured into the solution A slowly. They were stirred continuously, forming a yellow mixture suspension. The pH value thereof was adjusted to 7 by using ammonia water, and the resulting mixture was stirred thoroughly for 30 min, obtaining a BiVO 4 precursor solution. The prepared BiVO4 precursor solution was poured into a hydrothermal reaction kettle with a filling degree of 70%, heated to 180 °C and maintained at 180 °C for 12 h. After the reaction kettle was cooled to room temperature, the resulting product mixture was washed and dried, obtaining BiVO 4 .

[28] (2) Preparation of a protonated g-C3N4 powder: First, a crucible containing 15 g of melamine C 3 N3 (NH 2 ) 3 was placed in a muffle furnace, heated to 550 °C at a heating rate of 4 °C/min, calcined at 550 °C for 4 h, cooled to room temperature, and ground, obtaining a sample g-C3N4. 4 g of g-C3N4 was weighed and dissolved in 500 ml of 37% hydrochloric acid solution. They were sonicated for 60 min, and then stirred for 60 min. The resulting mixture was washed and dried, obtaining the protonated g-C3N4.

[29] (3) 0.1 g of BiVO 4 and 0.1 g of the protonated g-C3N4 were dissolved in 100 mL of ethanol. The resulting mixture was sonicated at room temperature for 1 h and then stirred in a fume hood for 24 h. After ethanol was volatilized, the resulting product was collected and dried at 60 °C for 12 h, obtaining a BiVO4/protonated g-C3N4 composite.

[30] (4) 0.1 g of the BiVO4/protonated g-C3N4 composite was dissolved in 50 ml of deionized water. The resulting mixture was sonicated for 10 min at room temperature. 851 L of 0.1 mol/L AgNO3 solution was added thereto. The resulting mixture was stirred for 1 h in the dark. 851 L of 0.1 mol/L KI solution was then added thereto dropwise during the stirring, and the stirring was continued for another 1 h. The resulting product mixture was washed and dried, obtaining the BiVO4/protonated

g-C3N4/AgI ternary composite photocatalyst.

[31] FIG. 1 shows XRD patterns of BiVO 4 , protonated g-C3N4 (pCN), AgI, BiVO4 /pCN, BiVO4/AgI, and BiVO4/pCN/AgI prepared in Example 1. The BiVO 4 diffraction peaks in the patterns are in agreement with the monoclinic phase of BiVO 4

(JCPDS No.14-0688), and the characteristic diffraction peaks are sharp, indicating that

the sample prepared by this method is monoclinic phase BiVO 4 with good crystallinity.

The two diffraction peaks of the protonated g-C3N4 located at 27.460 and 21.600 in the

pattern are respectively attributed to the (002) and (100) crystal planes of g-C3N4

(JCPDS No.87-1526), which are characteristics of carbon nitride layer-by-layer stacking

and regular arrangement of triazine rings in the plane. The diffraction peaks of AgI in

the pattern are in agreement with AgI (JCPDS 09-0374). For the XRD pattern of the

prepared BiVO4/protonated g-C3N4/AgI ternary composite photocatalyst, the pattern

contains all the diffraction peaks of monoclinic phase BiVO 4 and AgI, but no diffraction

peak of protonated g-C3N4 is detected, because of poor crystallization effect and low

strength after compounding.

[32] FIG. 2 is a TEM image of the BiVO4/protonated g-C3N4/AgI ternary composite photocatalyst as prepared in Example 1. It is observed that BiVO 4 and AgI are

distributed on protonated g-C3N4.

[33] FIG. 3 is a diagram showing the degradation effect of rhodamine B catalyzed by

BiVO 4 , protonated g-C3N4 (pCN), AgI, BiVO 4 /pCN, BiVO 4/AgI and the

BiVO4/pCN/AgI ternary composite photocatalyst as prepared in Example 1 under

visible light irradiation. The degradation ratio of the rhodamine B solution could reach

94.7% after being catalyzed by the BiVO4/protonated g-C3N4/AgI ternary composite

photocatalyst for 60 min, indicating that the prepared ternary composite photocatalyst

has excellent photocatalytic activity under visible light.

[34] Example 2

[35] (1) Preparation of a BiVO 4 powder: 10 mmol of bismuth nitrate Bi(N0 3 ) 3 -5H 2 0

was weighed and dissolved in 40 ml of deionized water. The resulting mixture was

stirred fully for 30 min, forming a solution A. 10 mmol of ammonium metavanadate

NH 4VO 3 was weighed and dissolved in 40 ml of deionized water. The resulting mixture

was stirred fully for 30 min, forming a solution B. The solution B was poured into the solution A slowly. They were stirred continuously, forming a yellow mixture suspension. The pH value thereof was adjusted to 7 by using ammonia water, and the resulting mixture was stirred thoroughly for 30 minutes, obtaining a BiVO 4 precursor solution. The prepared BiVO4 precursor solution was poured into a hydrothermal reaction kettle with a filling degree of 70%, heated to 180 °C and maintained at 180 °C for 12 h. After the reaction kettle was cooled to room temperature, the resulting product mixture was washed and dried, obtaining BiVO 4

.

[36] (2) Preparation of a protonated g-C3N4 powder: First, a crucible containing 15 g of melamine C 3 N3 (NH 2 ) 3 was placed in a muffle furnace, heated to 550 °C at a heating rate of 4 °C/min, calcined at 550 °C for 4 h, cooled to room temperature, and ground, obtaining a sample g-C3N4. 4 g of g-C3N4 was weighed and dissolved in 500 ml of 37% hydrochloric acid solution. The resulting mixture was sonicated for 60 min, and then stirred for 60 min. The resulting product mixture was washed and dried, obtaining the protonated g-C3N4.

[37] (3) 0.15 g of BiVO 4 and 0.1 g of the protonated g-C3N4 were dissolved in 100 mL of ethanol. The resulting mixture was sonicated at room temperature for 1 h and then stirred in a fume hood for 24 h. After ethanol was volatilized, the resulting product was collected and dried at 60 °C for 12 h, obtaining a BiVO4/protonated g-C3N4 composite.

[38] (4) 0.1 g of the BiVO4/protonated g-C3N4 composite was dissolved in 50 ml of deionized water. The resulting mixture was sonicated for 10 min at room temperature. 851 L of 0.1 mol/L AgNO3 solution was added thereto. The resulting mixture was stirred for 1 hour in the dark. 851 L of 0.1 mol/L KI solution was then added thereto dropwise during the stirring, and the stirring was continued for another 1 hour. The resulting product mixture was washed and dried, obtaining the BiVO4/protonated

g-C3N4/AgI ternary composite photocatalyst.

[39] After being catalyzed by the catalyst obtained in Example 2 for 60 min, the degradation ratio of the rhodamine B solution reached 92.5%.

Example 3

[40] (1) Preparation of a BiVO 4 powder: 10 mmol of bismuth nitrate Bi(N0 3 ) 3 -5H 2 0 was weighed and dissolved in 40 ml of deionized water. The resulting mixture was stirred fully for 30 min, forming a solution A. 10 mmol of ammonium metavanadate NH 4VO 3 was weighed and dissolved in 40 ml of deionized water. The resulting mixture was stirred fully for 30 min, forming a solution B. The solution B was poured into the solution A slowly. They were stirred continuously, forming a yellow mixture suspension. The pH value thereof was adjusted to 7 by using ammonia water, and the resulting mixture was stirred thoroughly for 30 minutes, obtaining a BiVO 4 precursor solution. The prepared BiVO4 precursor solution was poured into a hydrothermal reaction kettle with a filling degree of 70%, heated to 180 °C and maintained at 180 °C for 12 h. After the reaction kettle was cooled to room temperature, the resulting product mixture was washed and dried, obtaining BiVO 4 .

[41] (2) Preparation of a protonated g-C3N4 powder: First, a crucible containing 15 g melamine C 3 N3 (NH 2 ) 3 was placed in a muffle furnace, heated to 550 °C at a heating rate of 4 °C/min, and caicined at 550 °C for 4 h, cooled to room temperature, and ground, obtaining a sample g-C3N4. 4 g of g-C3N4 was weighed and dissolved in 500 ml of 37% hydrochloric acid solution. The resulting mixture was sonicated for 60 min, and then stirred for 60 min. The resulting product mixture was washed and dried, obtaining the protonated g-C3N4.

[42] (3) 0.2 g of BiVO 4 and 0.1 g of the protonated g-C3N4 were dissolved in 100 mL of ethanol. The resulting mixture was sonicated at room temperature for 1 h and then stirred in a fume hood for 24 h. After ethanol was volatilized, the resulting product was collected and dried at 60 °C for 12 h, obtaining a BiVO4/protonated g-C3N4 composite.

[43] (4) 0.1 g of the BiVO4/protonated g-C3N4 composite was dissolved in 50 ml of deionized water. The resulting mixture was sonicated for 10 min at room temperature. 851 L of 0.1 mol/L AgNO3 solution was added thereto. The resulting mixture was stirred for 1 h in the dark. 851 L of 0.1 mol/L KI solution was then added thereto dropwise during the stirring, and the stirring was continued for another 1 h. The resulting product mixture was washed and dried, obtaining the BiVO4/protonated g-C3N4/AgI ternary composite photocatalyst.

[44] After being catalyzed by the catalyst obtained in Example 3 for 60 minutes, the degradation ratio of the rhodamine B solution reached 90.3%.

[45] The above-mentioned embodiments are only the preferred embodiments of the present disclosure, and do not limit the scope of the present disclosure. Without departing from the design spirit of the present disclosure, various modifications and improvements to the technical solutions of the present disclosure made by those of ordinary skill in the art shall fall within the protection scope as defined in claims of the present disclosure.

Claims

CLAIMS:

1. A BiVO 4/protonated g-C3N4/AgI ternary composite photocatalyst, comprising

BiVO 4 , protonated g-C3N4, and AgI, wherein the composite photocatalyst is prepared by

steps of:

(1) preparation of a BiVO 4 powder: dissolving Bi(N0 3 )3-5H 20 in deionized water,

and fully stirring to form a solution A; dissolving NH 4 VO 3 in deionized water, and fully

stirring to form a solution B; pouring the solution B slowly into the solution A and

stirring continuously to form a yellow mixture suspension, adjusting a pH value thereof

to 7-9 by using ammonia water, and fully stirring to obtain a BiVO 4 precursor solution,

pouring the BiVO 4 precursor solution into a hydrothermal reaction kettle with a filling

degree of 70%, heating to a temperature of 180 °C, maintaining at the temperature and

subjecting the resulting mixture to a reaction for 12 h, cooling the reaction kettle to

room temperature, washing and drying to obtain the BiVO 4 powder;

(2) preparation of a protonated g-C3N4 powder: placing melamine into a muffle

furnace, heating to 550 °C at a heating rate of 4 °C/min, and calcining at 550 °C for 4 h,

cooling to room temperature, and grinding to obtain g-C3N4; dispersing the obtained

g-C3N4 in 37% hydrochloric acid solution, sonicating the resulting mixture for 60 min,

then stirring for 60 min, washing and drying to obtain the protonated g-C3N4;

(3) dissolving BiVO4 and the protonated g-C3N4 with a certain mass ratio in

ethanol, sonicating the resulting mixture at room temperature and then stirring in a fume

to obtain a BiVO4/protonated g-C3N4 composite;

(4) dissolving the BiVO4/protonated g-C3N4 composite in deionized water,

sonicating the resulting mixture at room temperature for 10 min and then adding a

2. The BiVO 4/protonated g-C3N4/AgI ternary composite photocatalyst as claimed in

claim 1, wherein in step (1), a molar ratio of Bi(N0 3) 3 -5H20 to NH4 VO 3 is 1 : 1.

3. The BiVO4/protonated g-C3N4/AgI ternary composite photocatalyst as claimed in

claim 1 or claim 2, wherein in step (2), a dosage ratioof g-C3N4 to the hydrochloric acid

solution is in the range of (1-4) g : (50-100) ml.

4. The BiVO4/protonated g-C3N4/AgI ternary composite photocatalyst as claimed in

any one of claims 1 to 3, wherein in step (3), a dosage ratio of BiVO 4 , the protonated

g-C3N4, and ethanol is in the range of (0.1-0.2) g : 0.1 g : 100 ml, and sonicating the

resulting mixture at room temperature is performed for 1-4 h; and in step (4), a dosage

ratio of the BiVO4/protonated g-C3N4 composite, deionized water, the AgNO3 solution,

and the KI solution is 0.1 g : 50 ml : 0.0851 mmol : 0.0851 mmol, the AgNO3 solution

has a AgNO3 concentration of 0.1 mol/L, and the KI solution has a KI concentration of

0.1 mol/L.

5. Use of the BiVO4/protonated g-C3N4/AgI ternary composite photocatalyst as

claimed in any one of claims 1-4 in the treatment of organic dyes.