Photocatalytic fuel cell as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of wastewater treatment, and particularly relates to a photocatalytic fuel cell as well as a preparation method and application thereof. The preparation method of the photocatalytic fuel cell comprises the following steps: preparing a precursor, calcining and packaging. The MeSy ZnO / ITO photo-anode prepared by adopting an electro-deposition-high-temperature sintering method has a layered structure, photo-generated holes can be generated to oxidize S < 2-> into sulfur, photo-generated electrons can be quickly transferred to an external circuit, compounding of photo-generated carriers is inhibited, and the MeSy ZnO / ITO photo-anode has excellent photoelectric properties; the constructed photocatalytic fuel cell can realize the purification of sulfide-containing wastewater under the conditions of visible light irradiation and no external bias voltage, and meanwhile, S < 2-> is recycled as sulfur to generate electricity and hydrogen peroxide, so that the recycling of sulfide is realized, and the environmental pollution is reduced. The problems that in the traditional sulfur-containing wastewater treatment process, the dosage of chemical agents is large, and the chemical energy of the chemical agents is not fully utilized are solved, and obvious economic benefits and environmental benefits are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment, and in particular relates to a photocatalytic fuel cell and a preparation method and application thereof. Background Art

[0002] Sulfide-containing wastewater generally refers to wastewater containing negative divalent sulfur (S 2- ) are mainly from the leather manufacturing industry, oil and gas industry, chemical production process and natural environment. In recent years, with the rapid development of modern industry, the discharge of sulfide-containing wastewater has increased rapidly. When sulfide is discharged directly into the water without treatment, it is easy to emit an unbearable odor, causing water quality deterioration, causing environmental damage, and seriously threatening human health. Therefore, sulfide-containing wastewater must be treated before it can be discharged into the environment.

[0003] At present, the main methods used to treat sulfide-containing wastewater are physical methods (stripping, adsorption and liquid membrane methods, etc.), biological methods (aerobic biological oxidation, anoxic biological treatment, etc.) and chemical methods (acidification absorption, chemical precipitation, chemical oxidation, electrocatalytic oxidation and photocatalytic oxidation, etc.). When treating sulfide-containing wastewater with physical methods, it is easy to generate gases such as SO2 and H2S, causing secondary pollution; biological methods have a long treatment cycle and poor applicability to high-concentration sulfide wastewater; chemical methods usually add a large amount of oxidants to S 2- Converted to S, S2O3 2- 、SO3 2- 、SO4 2- The products can be recycled and have the characteristics of fast reaction and simple operation. However, these methods require the addition of a large amount of chemical agents and frequent operations, which are difficult to meet the requirements of low-carbon environmental protection.

[0004] In recent years, the photocatalytic oxidation method driven by sunlight has attracted much attention due to its advantages of being green, economical, safe and sustainable. 2- Oxidized to S, S2O3 2- 、SO3 2- 、SO4 2- Under the action of appropriate catalysts, the sulfide ions can be oxidized and the H + Reduction to H2. It can be seen that the photocatalytic oxidation method can simultaneously realize the oxidation of sulfur ions and the production of H2, and is an effective method for harmless and resource-based treatment of sulfide-containing wastewater. Despite this, the current photocatalytic oxidation method only utilizes part of the chemical energy of sulfur ions when treating sulfide-containing wastewater, and the product H2 is not easy to transport and store. Therefore, the development of a resource-based treatment technology that can efficiently treat sulfide-containing wastewater and make full use of chemical energy has great application value. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a photocatalytic fuel cell and a preparation method and application thereof.

[0006] The object of the present invention is achieved by the following technical solution: A method for preparing a photocatalytic fuel cell, which comprises the following steps: S1. Preparation of precursor: Precursor MeS was obtained by electrodeposition y @Zn 0 / ITO, the MeS y It is a metal sulfide; S2. Calcination: The precursor MeS prepared in step S1 is y @Zn 0 / ITO was calcined at 300-400°C for 0.5-3h and then cooled to room temperature to obtain MeS y @ZnO / ITO photoanode; S3. Packaging: The MeS prepared in step S2 is y @ZnO / ITO photoanode and carbon material are used as photoanode and cathode of photocatalytic fuel cell respectively, the anode chamber and cathode chamber are separated by proton exchange membrane, and the electrodes are connected by wires and packaged to produce photocatalytic fuel cell.

[0007] As a preferred technical solution, the specific operation of preparing the precursor in step S1 is: placing 1-10 mmol / L zinc nitrate and 0.1-1 mol / L sodium sulfate in an electrolytic cell, using a zinc sheet as an anode and ITO (indium tin oxide conductive glass) as a cathode, and electroplating for 1-30 minutes under a DC voltage of 0.4-0.6 V to obtain Zn 0 / ITO; metal ions and sodium thiosulfate are used as electrolyte, the molar ratio of metal ions to sodium thiosulfate in the electrolyte is 1:1-10, graphite sheets are used as anodes and Zn 0 / ITO was used as the cathode and electroplated for 1 to 30 min at a DC voltage of 1.5 to 3.5 V to obtain MeS y @Zn 0 / ITO.

[0008] As a preferred technical solution, the metal sulfide is any one of cadmium sulfide, cuprous sulfide or indium zinc sulfide.

[0009] As a preferred technical solution, the carbon material in step S3 is graphite or nitrogen-modified graphite.

[0010] The preparation method of the nitrogen-modified graphite is as follows: melamine and graphite felt are mixed in a mass ratio of 50:1, the mixture is sintered at a temperature of 700° C. in an argon atmosphere for 2 hours, and the mixture is cooled to room temperature to obtain the nitrogen-modified graphite.

[0011] The photocatalytic fuel cell prepared by the above method.

[0012] The above-mentioned photocatalytic fuel cell is used in wastewater treatment.

[0013] As a preferred technical solution, the wastewater is sulfur-containing wastewater.

[0014] As a preferred technical solution, the specific operation of the wastewater treatment is as follows: injecting wastewater into the anode chamber of a photocatalytic fuel cell and adjusting the pH value of the anode chamber solution to 7-14, injecting an aqueous solution containing sodium sulfate into the cathode chamber of the photocatalytic fuel cell and adjusting the pH value of the cathode chamber solution to 2-7, then irradiating the anode chamber with visible light while introducing oxygen into the cathode chamber, stirring the reaction at room temperature for 0.1-3 hours; after stopping the reaction, adding acid to the anode chamber to adjust the pH value of the anode chamber solution to 1-2, forming a precipitate in the anode chamber, the obtained solid is sulfur, and the liquid is the treated effluent.

[0015] As a preferred technical solution, the light intensity is 0.5-1.5 Lux, and the stirring rate is 100-400 r / min.

[0016] Furthermore, the wastewater S 2- The ratio of mass to the area of ​​the photoanode is 1.5 to 6 mg:1 cm 2 The amount of oxygen introduced into the cathode chamber solution is 0.02-0.08 kg / m 3 *min, the concentration of sodium sulfate in the aqueous solution containing sodium sulfate is 2-4wt%.

[0017] The principle of the present invention is: In a photocatalytic fuel cell, the photoanode and cathode are connected by wires, and the anode chamber and cathode are separated by a proton exchange membrane. Under light, the photoanode generates electron-hole pairs, holes are enriched in the photoanode, and photoelectrons are transferred to the cathode through an external circuit; the sulfur ions in the photoanode chamber are oxidized by the holes enriched at the photoanode, and at the same time, the polysulfide solution produced by sulfur oxidation in the anode chamber is converted into sulfur by adjusting the pH; the oxygen in the cathode chamber is reduced to hydrogen peroxide by the electrons enriched in the cathode; the process of photoelectron migration through the external circuit generates current, realizing electricity generation.

[0018] In the photocatalytic fuel cell prepared by the present invention, MeS y@ZnO / ITO has a layered structure and gradient energy levels. The principle of preparing it by electrodeposition-high temperature sintering process is: electrodeposition is a method in which metal ions are deposited on electrodes under the action of a certain electrolyte and an external electric field. Under the action of an external electric field, Zn in zinc nitrate 2+ Reduced to Zn on the ITO (indium tin oxide conductive glass) cathode 0 , forming Zn 0 / ITO precursor. Then, sodium thiosulfate and metal chloride (MeCl x ) is the electrolyte. Under the action of an external electric field, sodium thiosulfate reacts with Zn 0 / ITO cathode is reduced to S 2- , while S 2- with Me x+ Generate MeS y and deposited on Zn 0 / ITO surface, forming a layered structure of MeS y @Zn 0 / ITO electrode precursor; again, MeS y @Zn 0 During the heating process of the ITO electrode precursor at high temperature, Zn 0 Transformed into ZnO, a layered structure (ZnO on MeS y and ITO) y @ZnO / ITO photoanode. In MeS y @Zn 0 In the ITO photoanode, MeS y Forming heterojunction with ZnO can promote MeS y The photogenerated electrons generated on MeS are quickly transferred to ZnO, and ZnO, as an electron transport layer, can quickly transfer the photoelectrons to ITO. y @ZnO / ITO is used in photocatalytic fuel cell anodes. y The electrons generated on the surface can be quickly transferred to the external circuit, and the generated photogenerated holes can 2- Selectively oxidizes sulfur. Since the generated sulfur will react with S 2- Polysulfides are generated, which can be converted into sulfur by adding sulfuric acid or hydrochloric acid.

[0019] When photoelectrons are transferred from the photoanode to the cathode through the external circuit, the O2 in the cathode chamber solution diffuses to the cathode surface, obtains electrons and is reduced. Since graphite or nitrogen-modified graphite can catalyze the two-electron reduction pathway of O2, O2 can be selectively reduced to hydrogen peroxide. Therefore, when MeS y When ZnO / ITO and graphite or nitrogen-modified graphite are used as the photoanode and cathode of photocatalytic fuel cells, respectively, S2- S is sulfur 2- The lost electrons are transferred to the external circuit and then to the cathode, where O2 is selectively reduced to hydrogen peroxide, thereby achieving the purpose of recovering sulfur, generating electricity and synthesizing hydrogen peroxide.

[0020] The present invention has the following advantages: (1) The present invention adopts the electrodeposition-high temperature sintering method to prepare MeS y @ZnO / ITO photoanode has a layered structure (ZnO is located on the MeS y and ITO), which can generate photogenerated holes to convert S 2- Oxidized to sulfur, it can also quickly transfer photogenerated electrons to the external circuit, inhibiting the recombination of photogenerated carriers and having excellent photoelectric properties; (2) The present invention uses graphite or nitrogen-modified graphite as the cathode to selectively reduce oxygen to hydrogen peroxide.

[0021] (3) The constructed photocatalytic fuel cell can purify sulfide-containing wastewater under visible light irradiation and without external bias. 2- It can be recovered as sulfur, generate electricity and hydrogen peroxide, and convert the chemical energy of sulfide into electrical energy, so as to solve the problems of large amount of chemical reagents added and insufficient utilization of chemical energy in the traditional sulfur-containing wastewater treatment process, which has obvious economic and environmental benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the principle of wastewater treatment using a photocatalytic fuel cell prepared by the method of the present invention. DETAILED DESCRIPTION

[0023] The present invention is further described below in conjunction with the accompanying drawings and embodiments, and the protection scope of the present invention is not limited to the following: Embodiment 1: A method for preparing a photocatalytic fuel cell, comprising the following steps: S1. Preparation of precursor: 1mmol / L zinc nitrate and 0.1mol / L sodium sulfate were placed in an electrolytic cell, with zinc sheet as anode and ITO as cathode, and electroplated for 30min at a DC voltage of 0.4V to obtain Zn 0 / ITO; metal cadmium ions and sodium thiosulfate are used as electrolytes, the molar ratio of metal ions to sodium thiosulfate in the electrolyte is 1:1, graphite sheets are used as anodes and Zn 0 / ITO was used as the cathode and electroplated for 30 min at a DC voltage of 1.5 V to obtain MeS y @Zn 0 / ITO, among which MeS y It is cadmium sulfide; S2. Calcination: The precursor MeS prepared in step S1 is y @Zn 0 / ITO was calcined at 300 °C for 3 h and then cooled to room temperature to obtain MeS y @ZnO / ITO photoanode; S3. Packaging: The MeS prepared in step S2 is y @ZnO / ITO photoanode and graphite are used as photoanode and cathode of photocatalytic fuel cell respectively, the anode chamber and cathode chamber are separated by proton exchange membrane, and the electrodes are connected by wires and packaged to produce photocatalytic fuel cell.

[0024] Embodiment 2: A method for preparing a photocatalytic fuel cell, comprising the following steps: S1. Preparation of precursor: 10mmol / L zinc nitrate and 1mol / L sodium sulfate were placed in an electrolytic cell, with zinc sheet as anode and ITO as cathode, and electroplated for 1min at a DC voltage of 0.6V to obtain Zn 0 / ITO; monovalent copper ions and sodium thiosulfate were used as electrolytes, the molar ratio of metal ions to sodium thiosulfate in the electrolyte was 1:10, graphite sheets were used as anodes and Zn 0 / ITO was used as the cathode and electroplated for 1 min at a DC voltage of 3.5 V to obtain MeS y @Zn 0 / ITO, among which MeS y It is cuprous sulfide; S2. Calcination: The precursor MeS prepared in step S1 is y @Zn 0 / ITO was calcined at 400 °C for 0.5 h and then cooled to room temperature to obtain MeS y @ZnO / ITO photoanode; S3. Packaging: The MeS prepared in step S2 is y @ZnO / ITO photoanode and nitrogen-modified graphite are used as photoanode and cathode of photocatalytic fuel cell, respectively. The anode chamber and cathode chamber are separated by a proton exchange membrane. The electrodes are connected by wires and packaged to obtain a photocatalytic fuel cell. Among them, nitrogen-modified graphite is prepared by the following method: melamine and graphite felt are mixed in a mass ratio of 50:1, the mixture is sintered at 700°C in an argon atmosphere for 2 hours, and then cooled to room temperature to obtain.

[0025] Embodiment 3: A method for preparing a photocatalytic fuel cell, comprising the following steps: S1. Preparation of precursor: 5mmol / L zinc nitrate and 0.6mol / L sodium sulfate were placed in an electrolytic cell, with zinc sheet as anode and ITO as cathode, and electroplated for 18min at a DC voltage of 0.5V to obtain Zn 0 / ITO; indium ions, zinc ions and sodium thiosulfate are used as electrolytes, the molar ratio of metal ions to sodium thiosulfate in the electrolyte is 1:6, and graphite sheets are used as anodes and Zn 0 / ITO was used as the cathode and electroplated for 18 min at a DC voltage of 2 V to obtain MeS y @Zn 0 / ITO, wherein the MeS y Indium zinc sulfide; S2. Calcination: The precursor MeS prepared in step S1 is y @Zn 0 / ITO was calcined at 365 °C for 1.8 h and then cooled to room temperature to obtain MeS y @ZnO / ITO photoanode; S3. Packaging: The MeS prepared in step S2 is y @ZnO / ITO photoanode and graphite are used as photoanode and cathode of photocatalytic fuel cell respectively, the anode chamber and cathode chamber are separated by proton exchange membrane, and the electrodes are connected by wires and packaged to produce photocatalytic fuel cell.

[0026] Example 4: A method for treating wastewater, wherein wastewater is injected into the anode chamber of a photocatalytic fuel cell and the pH value of the anode chamber solution is adjusted to 7, an aqueous solution containing sodium sulfate is injected into the cathode chamber of the photocatalytic fuel cell and the pH value of the cathode chamber solution is adjusted to 2, and then the anode chamber is irradiated with visible light while oxygen is introduced into the cathode chamber, and the reaction is stirred at room temperature for 0.1h; after stopping the reaction, an acid is added to the anode chamber to adjust the pH value of the anode chamber solution to 1, a precipitate is formed in the anode chamber, the obtained solid is sulfur, and the liquid is treated effluent. The principle of wastewater treatment is as follows Figure 1 shown.

[0027] Wherein, the illumination intensity is 0.5 Lux, the stirring rate is 100 r / min; 2- The ratio of mass to the area of ​​the photoanode is 1.5 mg:1 cm 2 The amount of oxygen introduced into the cathode chamber solution is 0.02 kg / m 3 *min, the concentration of sodium sulfate in the aqueous solution containing sodium sulfate is 2wt%.

[0028] Example 5: A method for treating wastewater, wherein wastewater is injected into the anode chamber of a photocatalytic fuel cell and the pH value of the anode chamber solution is adjusted to 14, an aqueous solution containing sodium sulfate is injected into the cathode chamber of the photocatalytic fuel cell and the pH value of the cathode chamber solution is adjusted to 7, and then the anode chamber is irradiated with visible light while oxygen is introduced into the cathode chamber, and the reaction is stirred at room temperature for 3 hours; after stopping the reaction, an acid is added to the anode chamber to adjust the pH value of the anode chamber solution to 2, a precipitate is formed in the anode chamber, the obtained solid is sulfur, and the liquid is treated effluent. The principle of wastewater treatment is as follows Figure 1 shown.

[0029] The illumination intensity is 1.5 Lux, the stirring rate is 400 r / min, and the S in the wastewater is 2- The mass ratio of the photoanode to the area of ​​the photoanode is 6 mg:1 cm 2 The amount of oxygen introduced into the cathode chamber solution is 0.08 kg / m 3 *min, the concentration of sodium sulfate in the aqueous solution containing sodium sulfate is 4wt%.

[0030] Example 6: A method for treating wastewater, wherein wastewater is injected into the anode chamber of a photocatalytic fuel cell and the pH value of the anode chamber solution is adjusted to 10, an aqueous solution containing sodium sulfate is injected into the cathode chamber of the photocatalytic fuel cell and the pH value of the cathode chamber solution is adjusted to 5, and then the anode chamber is irradiated with visible light while oxygen is introduced into the cathode chamber, and the reaction is stirred at room temperature for 1.5 hours; after stopping the reaction, an acid is added to the anode chamber to adjust the pH value of the anode chamber solution to 1.5, a precipitate is formed in the anode chamber, the obtained solid is sulfur, and the liquid is treated effluent. The principle of wastewater treatment is as follows Figure 1 shown.

[0031] Wherein, the illumination intensity is 1 Lux, the stirring rate is 220 r / min; 2- The mass ratio of the photoanode to the area of ​​the photoanode is 3 mg:1 cm 2 The amount of oxygen introduced into the cathode chamber solution is 0.04 kg / m 3 *min, the concentration of sodium sulfate in the aqueous solution containing sodium sulfate is 3wt%.

[0032] Experimental Example 1: Treatment of wastewater from an oil and gas field using the photocatalytic fuel cell prepared in Example 1 Wastewater from an oil and gas field, S 2- The concentration is 389.0 mg / L, the pH is 6.5, the TOC is 80.5 mg / L, and the conductivity is 4.52 mS / m. Take 1L of the wastewater into the anode chamber of the photocatalytic fuel cell; the size of the photoanode is 30 cm long × 4 cm wide × 0.1 cm thick; the size of the cathode graphite is 30 cm long × 4 cm wide × 0.1 cm thick; then irradiate the anode chamber with visible light and add 1L of 3wt% sodium sulfate solution into the cathode chamber, and introduce 0.025 kg / m3 *min, stirred at room temperature for 3h, and the intensity of the visible light was 1Lux. After the illumination, S 2- The removal rate is 92.8%, the concentration of hydrogen peroxide obtained in the cathode chamber is 19 mmol / L, and sulfuric acid is added to the anode chamber until the solution pH = 1 to obtain sulfur.

[0033] Experimental Example 2: Treating leather wastewater using the photocatalytic fuel cell prepared in Example 1 A leather wastewater, S 2- The concentration is 5040mg / L, the pH is 12.3, the TOC is 2700mg / L, and the conductivity is 3.19mS / m. Take 5L of the wastewater to the anode chamber of the photocatalytic fuel cell; the size of the photoanode is 60 length × 10 width × 0.1cm height, and the size of the cathode graphite is 60 length × 10 width × 0.1cm height; then irradiate the anode chamber with visible light, and add 5L of 3wt% sodium sulfate solution to the cathode chamber, and introduce 0.04kg / m 3 *min, stirred at room temperature for 2h, the intensity of the visible light was 1Lux. After the illumination, the removal rate of sulfur ions in the anode chamber was 61.2%, the concentration of hydrogen peroxide in the cathode chamber was 840mmol / L, sulfuric acid was added to the anode chamber until the solution pH = 1, and sulfur was obtained.

[0034] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which are all covered by the protection scope of the present invention.

Claims

1. A method for preparing a photocatalytic fuel cell, characterized in that: It includes the following steps: S1. Preparation of precursor: Precursor MeS was obtained by electrodeposition y @Zn 0 / ITO, the MeS y It is a metal sulfide; S2. Calcination: The precursor MeS prepared in step S1 is y @Zn 0 / ITO was calcined at 300-400°C for 0.5-3h and then cooled to room temperature to obtain MeS y @ZnO / ITO photoanode; S3. Packaging: The MeS prepared in step S2 is y @ZnO / ITO photoanode and carbon material are used as photoanode and cathode of photocatalytic fuel cell respectively, the anode chamber and cathode chamber are separated by proton exchange membrane, and the electrodes are connected by wires and packaged to produce photocatalytic fuel cell.

2. The method for preparing a photocatalytic fuel cell according to claim 1, characterized in that: The specific operation of preparing the precursor in step S1 is: placing 1-10 mmol / L zinc nitrate and 0.1-1 mol / L sodium sulfate in an electrolytic cell, using a zinc sheet as an anode and ITO as a cathode, and electroplating for 1-30 min under a DC voltage of 0.4-0.6 V to obtain Zn 0 / ITO; metal ions and sodium thiosulfate are used as electrolyte, the molar ratio of metal ions to sodium thiosulfate in the electrolyte is 1:1-10, graphite sheets are used as anodes and Zn 0 / ITO was used as the cathode and electroplated for 1 to 30 min at a DC voltage of 1.5 to 3.5 V to obtain MeS y @Zn 0 / ITO.

3. The method for preparing a photocatalytic fuel cell according to claim 1, characterized in that: The metal sulfide is any one of cadmium sulfide, cuprous sulfide or indium zinc sulfide.

4. The method for preparing a photocatalytic fuel cell according to claim 1, characterized in that: The carbon material in step S3 is graphite or nitrogen-modified graphite.

5. A photocatalytic fuel cell prepared according to the method described in any one of claims 1 to 4.

6. Use of the photocatalytic fuel cell according to claim 5 in wastewater treatment.

7. The use according to claim 6, characterized in that: The wastewater is sulfur-containing wastewater.

8. The use according to claim 7, characterized in that: The specific operation of the wastewater treatment is: injecting wastewater into the anode chamber of the photocatalytic fuel cell and adjusting the pH value of the anode chamber solution to 7-14, injecting an aqueous solution containing sodium sulfate into the cathode chamber of the photocatalytic fuel cell and adjusting the pH value of the cathode chamber solution to 2-7, then irradiating the anode chamber with visible light while introducing oxygen into the cathode chamber, stirring at room temperature for 0.1-3 hours; after stopping the reaction, adding acid into the anode chamber to adjust the pH value of the anode chamber solution to 1-2, forming a precipitate in the anode chamber, the obtained solid is sulfur, and the liquid is treated effluent.

9. The use according to claim 8, characterized in that: The light intensity is 0.5-1.5 Lux, and the stirring rate is 100-400 r / min.

10. The use according to claim 8, characterized in that: The S in the wastewater 2- The ratio of mass to the area of ​​the photoanode is 1.5 to 6 mg:1 cm 2 The amount of oxygen introduced into the cathode chamber solution is 0.02-0.08 kg / m 3 *min, the concentration of sodium sulfate in the aqueous solution containing sodium sulfate is 2-4wt%.

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