CN107952464B

CN107952464B - Novel photocatalytic material and double-photocatalytic-electrode self-bias pollution control system

Info

Publication number: CN107952464B
Application number: CN201711324886.5A
Authority: CN
Inventors: 柳丽芬; 拉贝; 张艺臻
Original assignee: Dalian University of Technology
Current assignee: Dalian University of Technology
Priority date: 2017-12-13
Filing date: 2017-12-13
Publication date: 2020-09-11
Anticipated expiration: 2037-12-13
Also published as: CN107952464A

Abstract

The invention provides a novel photocatalytic material and a double-photocatalytic-electrode self-bias pollution control system, and belongs to the technical field of sewage treatment and energy recycling. Synthesis of excellent ternary composite g-C by using cheap material₃N₄‑Fe⁰‑TiO₂The photocatalyst improves visible light absorption, and the heterojunction of the photocatalyst promotes electron hole separation so as to improve the photocatalytic performance. Using g-C₃N₄‑Fe⁰‑TiO₂As anodes for photocatalytic self-biasing systems, WO₃The photocatalyst is used as a cathode, and the constructed double electrodes expand the Fermi energy level difference between the electrodes and improve the electricity generation performance of the photocatalytic self-bias system. The invention has the effects and benefits that the novel ternary heterojunction photocatalyst is used as the anode, the cathode is reasonably matched, the Fermi energy level difference between the electrodes is enlarged, the self-bias system with high yield performance is constructed, the treatment of the organic wastewater difficult to degrade is realized, and the same time is used for treating the organic wastewater difficult to degradeThe electric energy can be efficiently output within a wider pH range.

Description

Novel photocatalytic material and double-photocatalytic-electrode self-bias pollution control system

Technical Field

The invention belongs to the technical field of energy and sewage treatment, and relates to a novel ternary heterojunction photocatalytic material applied to a double-photocatalytic electrode self-bias pollution control system, which drives and realizes electron transfer, and can realize high-efficiency electric energy output in a wide pH range while treating organic wastewater difficult to degrade.

Background

The photocatalysis technology is an environment management technology which integrates the advantages of high efficiency, energy conservation, simple operation and the like. The photocatalytic fuel cell developed in recent years is a novel fuel cell system, and a closed circuit is formed by connecting a photocatalytic anode and a photocatalytic cathode through a lead. Under the action of illumination, the semiconductor anode photocatalytic material of the system generates electrons and holes, the photoproduction holes oxidize and degrade pollutants in the anode chamber, the photoproduction electrons are transferred to the cathode through an external circuit to form a closed loop to generate electricity, and simultaneously the photoproduction electrons and H transferred from the anode can be simultaneously transferred under the anaerobic condition⁺Reaction to form H₂In the presence of oxygen, the oxygen can be reduced to produce water. The system realizes electric energy output while degrading the wastewater, realizes energy conservation and emission reduction and energy recovery, and has obvious environmental benefit, economic benefit and social benefit. Research on photocatalytic fuel cells (photocatalytic self-bias systems) mainly focuses on research construction on electrode materials, and selection of the photocatalytic electrode materials is an important factor influencing the system yield level and the degradation efficiency of pollutants.

TiO₂The photocatalyst is a typical n-type semiconductor photocatalyst which is most widely used, and has stable chemical properties, simple and convenient synthesis and low price; however, the band gap width is 3.2eV, the photocatalyst can only be excited by ultraviolet light, and the recombination probability of photogenerated holes and electrons is high, so that the photocatalytic efficiency is reduced. Thus, TiO is added₂The photocatalyst can be combined with other semiconductor catalysts with narrower forbidden band widths to improve the photocatalytic effect of the semiconductor catalysts. g-C₃N₄Is a visible light catalyst with narrower forbidden band width, has large specific surface area and unique electronic structure, and can be used for pollutant degradation, photocatalytic hydrogen production and the likeThe catalyst has excellent performance and good photoelectrochemical performance, and is a visible light electric catalyst with good application prospect. Recent research shows that the ternary heterojunction has higher catalytic activity, and the ternary heterojunction catalyst has higher catalytic activity and stability than the binary heterojunction catalyst. Ag₃PO₄/Ag/BiVO₄(040) Ternary Z-structure heterojunction catalysts enhance triclosan degradation under visible light (Chen F, Yang Q, Li X, equivalent. hierarchical association of graphene-bridged Ag₃PO₄/Ag/BiVO₄(040)Z-schemephotocatalyst:An efficient,sustainable and heterogeneous catalyst withenhanced visible-light photoactivity towards tetracycline degradation undervisible light irradiation[J]Applied Catalysis B: Environmental,2017,200: 330-. In addition, for the photocatalytic self-bias system, different photocatalytic anode and cathode materials have different Fermi energy level differences, and electron transfer is driven and realized, so that the selection of a proper photocatalytic cathode and anode material is crucial to the improvement of system power generation, the improvement of light source utilization rate and photo-generated electron transfer efficiency, and the improvement of the performance of the self-bias system. Therefore, the invention aims to provide a novel ternary heterojunction high-activity photocatalytic electrode material, which is matched with a reasonably selected cathode material to construct a self-bias system with larger inter-electrode Fermi energy level difference, drive and realize electron transfer, and realize simultaneous high-efficiency power generation and degradation-resistant wastewater treatment in a wide pH range under the condition of not adding a chemical oxidation reagent.

Disclosure of Invention

The invention prepares the ternary heterojunction g-C by using a simple method of cheap materials₃N₄-Fe⁰-TiO₂The photocatalyst enhances the visible light absorption and electron hole separation effects, improves the photocatalytic degradation effect, and is coupled with WO as an anode material₃As a cathode material, a photocatalytic self-bias system for enlarging the Fermi energy level difference between electrode materials is constructed, the system is used for improving the power generation of the system, and the active oxygen species generated in the system are used for treating the refractory wastewater.

The technical scheme of the invention is as follows:

novelThe photocatalytic material and double photocatalytic electrode self-bias pollution control system comprises a reactor, an aeration device and an electrogenesis collection system; the reactor is a square quartz single-chamber reactor, g-C₃N₄-Fe⁰-TiO₂Electrodes as anodes placed on one side of the reactor, WO₃The photocatalyst is used as a cathode and is arranged at the other side in the reactor, a resistor is connected between the cathode and the anode to form a circuit, and an aeration device is arranged at the bottom of the circuit;

said g-C₃N₄-Fe⁰-TiO₂The powder preparation steps are as follows:

(1)Fe⁰/TiO₂preparation: according to Fe⁰With TiO₂Is 0.2 to 10 percent by mass to TiO₂Adding FeSO into the powder₄·7H₂Dissolving in deionized water after O, and adding NaBH₄Adding a reducing agent according to a stoichiometric ratio, reducing for 30-60min in a nitrogen atmosphere, centrifuging, washing for several times, and drying at 60 ℃ to obtain Fe⁰/TiO₂Standby;

(2)g-C₃N₄/Fe⁰/TiO₂preparation: roasting melamine at 550 ℃ for 4h to obtain g-C₃N₄Powder of g-C₃N₄Adding the powder into HCl solution with the mass percent of 18.5 wt%, wherein the concentration of the solution is 0.001-0.003g/mL, and washing and drying for later use after ultrasonic dispersion; taking g-C after acid treatment₃N₄The prepared concentration of the powder is 1mg/mL g-C₃N₄Solution, ultrasonic dispersion to obtain g-C₃N₄A nanosheet solution; dissolving 1.5mg/mL Fe in deionized water⁰/TiO₂Solution, 1mg/mL g-C₃N₄Mixing the nanosheet solution and 5-10 wt% of polyethylene glycol 2000 solution according to a volume ratio of 200:1:10, performing ultrasonic dispersion, reacting for 1h at 70 ℃ water bath temperature, performing centrifugal separation and washing for several times, and drying at 60 ℃ to obtain the g-C₃N₄/Fe⁰/TiO₂And (3) powder.

Said WO₃The preparation method of the photocatalyst comprises the following steps:

preparing 0.34mol/L sodium tungstate aqueous solution, dropwise adding 3mol/L hydrochloric acid solution, stirring until no precipitate is generated, wherein the volume ratio of the sodium tungstate aqueous solution to the hydrochloric acid solution is about25:1, standing the solution until the solution is gelatinous; adding 0.10-0.2mol/L CTAB solution into the gel at a volume ratio of 10:3, ultrasonically dispersing, centrifuging, washing, drying, and roasting at 600 deg.C for 2-3h to obtain WO₃And (3) powder.

The preparation method of the photocatalytic electrode comprises the steps of pretreating and cleaning conductive substrate materials such as stainless steel meshes, carbon fiber cloth, carbon felts and the like, and then respectively adding the binder into g-C₃N₄/Fe⁰/TiO₂And WO₃And (3) uniformly mixing the powder by ultrasonic waves, and coating the powder on a conductive substrate to obtain the photocatalytic electrode.

The novel double-photocatalysis electrode self-bias pollution control system simultaneously realizes high-performance electricity generation and degradation of refractory dyes, antibiotics and coking wastewater within the pH range of 2-10.

The invention has the beneficial effects that: the invention utilizes cheap materials to prepare g-C₃N₄-Fe⁰-TiO₂The composite material enhances the absorption and utilization of light, promotes the separation of electrons and holes, and improves the photocatalytic activity; with WO₃The composite material is used as a cathode and applied to a photocatalytic self-bias system, the Fermi energy level difference between electrode materials is enlarged to drive electron transfer, high-efficiency electricity generation under a wide pH range is realized, and pollutants difficult to degrade are treated.

Drawings

FIG. 1 is g-C of the present invention₃N₄-Fe⁰-TiO₂TEM image of the catalyst.

FIG. 2 is g-C of the present invention₃N₄-Fe⁰-TiO₂EDS diagram of catalyst.

FIG. 3 is g-C of the present invention₃N₄-Fe⁰-TiO₂、Fe⁰-TiO₂、g-C₃N₄And TiO₂Photo-catalytic composite contrast UV-visDRS plot.

FIG. 4 is g-C of the present invention₃N₄-Fe⁰-TiO₂Anode, WO₃A cathode constructs a photocatalytic self-bias system, and the system degrades a graph of 10mg/L rhodamine B under (without) visible light under visible light with different pH values; wherein the abscissa represents time in minutes and the ordinate representsAnd (4) dividing rate.

FIG. 5 is g-C of the present invention₃N₄-Fe⁰-TiO₂Anode, WO₃A cathode constructs a photocatalytic self-bias system, and the system is in a potential diagram under visible light with different pH values; (a) pH 2 (b) pH 5 (c) pH 7 (d) pH 10; where the abscissa represents time in minutes and the ordinate represents voltage in volts.

FIG. 6 is g-C of the present invention₃N₄-Fe⁰-TiO₂Anode, WO₃Constructing a photocatalytic self-bias system by the cathode, and carrying out a potential diagram of the system under the condition of different pH values and keeping out of the sun; where the abscissa represents time in minutes and the ordinate represents voltage in volts.

Detailed Description

The following further describes a specific embodiment of the present invention with reference to the drawings and technical solutions.

Example 1:

g-C₃N₄-Fe⁰-TiO₂preparation of photocatalytic powder:

(1)Fe⁰/TiO₂preparation: according to Fe⁰With TiO₂In a mass ratio of 0.5% to TiO₂Adding FeSO into the powder₄·7H₂Adding O into 50ml deionized water, ultrasonically dispersing for 30min, introducing nitrogen for 30min, and adding 0.0136g NaBH₄Reducing for 30min under nitrogen atmosphere, centrifuging and washing for several times, and drying at 60 ℃ for later use.

(2)g-C₃N₄/Fe⁰/TiO₂Preparation: roasting melamine at 550 ℃ for 4h to obtain g-C₃N₄Powder of 1.00g g-C₃N₄Adding HCl (18.5 wt%) into the powder, performing ultrasonic treatment for 4 hours to fully disperse the HCl, adding 500ml deionized water to dilute, performing centrifugal washing for several times until the solution is neutral, and drying at 105 ℃ to obtain g-C₃N₄Nanosheets. Weighing the above g-C₃N₄Dissolving the nano-sheet powder in deionized water, controlling the concentration at 1mg/mL, and performing ultrasonic treatment for 6 hours to obtain uniform g-C₃N₄A nanosheet solution. 300mg of prepared Fe was weighed⁰/TiO₂Dissolving the catalyst in 200ml deionized water, and performing ultrasonic treatment for 30minAdding 1.0mL of 5 wt% polyethylene glycol 2000 solution, uniformly dispersing by ultrasonic wave, and adding 10mL of 1mg/mL g-C₃N₄Reacting the nanosheet solution in water bath at 70 ℃ for 1h, centrifugally separating and washing for a plurality of times, and drying at 60 ℃ to obtain the g-C₃N₄/Fe⁰/TiO₂Grinding the powder, and sieving the powder with a 120-mesh sieve for later use. In the TEM image of FIG. 1 and the EDS elemental distribution chart of FIG. 2, it can be seen that g-C was successfully prepared₃N₄/Fe⁰/TiO₂The nano-scale composite material has a good ternary composite nano-scale microstructure, forms a heterojunction composite structure, and is uniformly dispersed. FIG. 3 is a UV-visible diffuse reflectance plot comparing ternary composite g-C₃N₄/Fe⁰/TiO₂，Fe⁰/TiO₂，TiO₂And g-C₃N₄It can be seen that g-C is in the visible region₃N₄/Fe⁰/TiO₂The absorbance of the ternary composite structure is strongest and is better than that of binary composite.

Example 2

g-C prepared in example 1₃N₄-Fe⁰-TiO₂Mixing the photocatalytic powder and the silica sol according to the proportion of 1mg:1 mu L, performing ultrasonic dispersion to obtain uniform suspension, uniformly coating the uniform suspension on the surface of the pretreated stainless steel net, and naturally drying.

Self-biasing system WO₃The preparation method of the photocatalytic cathode comprises the following steps: 50ml of 0.34mol/L sodium tungstate aqueous solution is prepared, about 2ml of 3mol/L hydrochloric acid solution is added, the mixture is continuously stirred until no precipitate is generated, and the mixture is placed for 24 hours to form gel. Adding 15ml of 0.15mol/L CTAB into the gel, performing ultrasonic dispersion for 40min, performing centrifugal separation, washing and drying, and roasting at 600 ℃ for 2h to obtain WO₃Grinding the powder, and sieving the powder with a 120-mesh sieve for later use. Mixing the prepared catalyst powder and 1 mg/1 mu L of silica sol, ultrasonically dispersing into uniform suspension, uniformly coating on the surface of a pretreated stainless steel net, and naturally drying.

The bi-photocatalytic electrode self-bias system operates: 450ml of a single-chamber reactor containing 10mg/L rhodamine B and 0.05mol/L NaSO is added into the reactor with the volume of 100mm, 50mm and 200mm₄Wastewater was simulated and pH was adjusted to 2, 5, 7, 10 with hydrochloric acid and sodium hydroxide. g-C₃N₄/Fe⁰/TiO₂Electrode for electrochemical cellAs an anode on one side of the reactor, WO₃The electrode is used as a cathode and is arranged at the other side of the reactor, an external circuit is connected with a 10 omega resistor, a 50W cold reflection halogen tungsten lamp is used as a light source, the distance between the light source and the reactor is 5cm, and the bottom of the reactor is continuously aerated to provide sufficient dissolved oxygen for generating oxygen free radicals by electron activation of oxygen. Before the reaction starts, air is exposed and stirred, the mixture is adsorbed in the dark for 30min to achieve adsorption-desorption balance, a 50W cold reflection tungsten halogen lamp is turned on, samples are taken once every 10min, and an ultraviolet visible spectrophotometer is used for measuring the absorbance value at the position with the wavelength of 554 nm. The results in fig. 4 show that the double photocatalytic electrode self-bias system has greater degradation effect under visible light irradiation under the conditions of

pH

2, 5, 7 and 10 than that without light, the degradation rate is 90% under neutral condition, and the degradation rate reaches 94% under the condition of pH 2, which indicates that H is provided under acidic condition⁺Promoting the photocatalytic reaction.

Example 3

The reaction system has the same composition as the reaction system in the embodiment 2, and a computer is connected with a data acquisition unit to record the potential under the conditions of visible light and dark light in the operation process. FIG. 5 shows the system power generation under pH 2, pH 5, pH 7 and pH 10, the cell potential is 0.7V under neutral condition, and the system power generation effect is further improved to about 0.9V in acidic and alkaline solutions; the potential of the reactor cell is kept at about 0.5V under the condition of pH 2-10 in a dark condition, and the stability is better when the reactor runs at pH 2 and pH 7 (figure 6).

Claims

1. The double-photocatalytic electrode self-bias pollution control system is characterized by comprising a reactor, an aeration device and an electrogenesis collection system; the reactor is a square quartz single-chamber reactor, g-C₃N₄-Fe⁰-TiO₂Electrodes as anodes placed on one side of the reactor, WO₃The photocatalyst is used as a cathode and is arranged at the other side in the reactor, a resistor is connected between the cathode and the anode to form a circuit, and an aeration device is arranged at the bottom of the circuit;

said g-C₃N₄-Fe⁰-TiO₂The powder preparation steps are as follows:

(1)Fe⁰/TiO₂preparation: according to Fe⁰With TiO₂Is 0.2 to 10 percent by mass to TiO₂Adding FeSO into the powder₄·7H₂Dissolving in deionized water after O, and adding NaBH₄Adding a reducing agent according to a stoichiometric ratio, reducing for 30-60min in a nitrogen atmosphere, centrifugally washing for several times, and drying at 60 ℃ to obtain Fe⁰/TiO₂Standby;

(2)g-C₃N₄/Fe⁰/TiO₂preparation: roasting melamine at 550 ℃ for 4h to obtain g-C₃N₄Powder of g-C₃N₄Adding the powder into HCl solution with the mass percent of 18.5 wt%, wherein the concentration of the solution is 0.001-0.003g/mL, and washing and drying for later use after ultrasonic dispersion; taking g-C after acid treatment₃N₄The powder preparation concentration is 1mg/mL g-C₃N₄Solution, ultrasonic dispersion to obtain g-C₃N₄A nanosheet solution; dissolving 1.5mg/mL Fe in deionized water⁰/TiO₂Solution, 1mg/mL g-C₃N₄Mixing the nanosheet solution and 5-10 wt% of polyethylene glycol 2000 solution according to a volume ratio of 200:1:10, performing ultrasonic dispersion, reacting for 1h at 70 ℃ water bath temperature, performing centrifugal separation and washing for several times, and drying at 60 ℃ to obtain the g-C₃N₄/Fe⁰/TiO₂Powder;

preparing 0.34mol/L sodium tungstate aqueous solution, dropwise adding 3mol/L hydrochloric acid solution, stirring until no precipitate is generated, wherein the volume ratio of the sodium tungstate aqueous solution to the hydrochloric acid solution is 25:1, and standing the solution until the solution is gelatinous; adding 0.10-0.2mol/L CTAB solution into the gel at a volume ratio of 10:3, ultrasonically dispersing, centrifuging, washing, drying, and roasting at 600 deg.C for 2-3h to obtain WO₃And (3) powder.

2. The dual-photocatalytic electrode self-bias pollution control system as claimed in claim 1, wherein the photocatalytic electrode is prepared by pre-treating and cleaning a stainless steel mesh, carbon fiber cloth or carbon felt conductive substrate material, and then adding a binder to g-C₃N₄/Fe⁰/TiO₂And WO₃And (3) uniformly mixing the powder by ultrasonic waves, and coating the powder on a conductive substrate to obtain the photocatalytic electrode.

3. The bi-photocatalytic electrode self-bias pollution control system as claimed in claim 1 or 2, which can simultaneously realize high-performance electricity generation and degradation of refractory dyes, antibiotics or coking wastewater in the pH range of 2-10.