Photocatalytic fuel cell based on cadmium sulfide titanium dioxide composite photo-anode and application

Abstract

The invention relates to a photocatalytic fuel cell based on a cadmium sulfide titanium dioxide composite photo-anode and application, and relates to the technical field of preparation of novel photo-electrode materials, the cell adopts a continuous ion deposition method to prepare a CdS quantum dot modified TiO2 photo-anode with a specific layer number, and the CdS quantum dot modified TiO2 photo-anode, a platinum cathode and an ion exchange membrane form a synergistic system. The layer number and the particle size of CdS quantum dots in the photo-anode are accurately controlled, an efficient heterojunction structure is constructed, and the visible light utilization and charge separation efficiency is improved to the maximum extent; a chemical bonding effect is formed on the surface of the photo-anode by using carboxyl-containing organic fuel, so that an electron transmission path is obviously accelerated; the dual functions of organic wastewater degradation and electric energy synchronous output are achieved, and long-term operation stability is kept. The technology provides an efficient and low-consumption solution for resourceful treatment of industrial organic wastewater.

Description

Technical Field

[0001] The present invention relates to the technical field of novel photoelectrode material preparation, in particular to a photocatalytic fuel cell based on a cadmium sulfide-titanium dioxide composite photoanode and its application. Background Art

[0002] With the rapid development of industrialization, the global energy crisis and water pollution are becoming increasingly severe. Traditional wastewater treatment technologies (such as biological and adsorption methods) suffer from high energy consumption and low resource recovery rates. While conventional fuel cells can achieve energy conversion, they rely on precious metal catalysts and high-purity fuels, resulting in high application costs. Therefore, the development of new treatment technologies that combine efficient pollutant degradation with the simultaneous output of clean energy has become a research hotspot.

[0003] Photoelectrocatalytic fuel cell (PFC) technology uses a photoanode to excite electron-hole pairs under illumination, driving the oxidative degradation of organic matter in the fuel while simultaneously outputting electrical energy through an external circuit, achieving an integrated "pollution control and power generation" process. Since Bard first proposed this concept in 1976, its core bottleneck has been the light absorption efficiency and charge separation capabilities of the photoanode material. Titanium dioxide (TiO2) is a commonly used photoanode material due to its excellent stability, non-toxicity, and low cost. However, its wide bandgap (~3.2 eV) results in a visible light utilization rate of less than 5%, severely restricting its practical application.

[0004] Therefore, a photocatalytic fuel cell based on a cadmium sulfide titanium dioxide composite photoanode and its application are needed to solve the above problems. Summary of the Invention

[0005] In order to solve the problems of the prior art, the present invention provides a photocatalytic fuel cell based on a cadmium sulfide-titanium dioxide composite photoanode and its application.

[0006] In order to solve the above technical problems, the present invention is achieved through the following technical solutions: In the first aspect, a photocatalytic fuel cell based on a cadmium sulfide titanium dioxide composite photoanode comprises:

[0007] Photoanode: It consists of a TiO2 substrate and a CdS quantum dot layer deposited on its surface. The CdS quantum dot layer is prepared by continuous ion deposition. The specific steps are as follows:

[0008] The TiO2 electrode was immersed in cadmium nitrate solution and sodium sulfide solution for 1 minute each to form a single layer of CdS quantum dots;

[0009] Repeat the above deposition steps until the number of CdS layers is 6 to obtain a 6CdS / TiO2 composite photoanode;

[0010] Cathode: platinum (Pt) electrode;

[0011] Isolation component: The cathode and photoanode are isolated by an ion exchange membrane;

[0012] Fuel supply system: using organic matter containing carboxyl functional groups as fuel, the organic matter includes at least one of formic acid, methanol, and glucose.

[0013] In this aspect, by constructing a CdS quantum dot-modified TiO2 composite photoanode (6CdS / TiO2), the photoelectric conversion efficiency and organic wastewater treatment performance of the photocatalytic fuel cell were significantly improved. Experiments show that the deposition of 6 layers of CdS quantum dots can optimize the photoanode band structure, and its nanoscale particle size (2-5nm) forms a heterojunction with TiO2, effectively broadening the light response range to the visible light region, while inhibiting the recombination of photogenerated electrons and holes, thereby increasing the photocurrent density by 2.3 times compared to pure TiO2. In terms of fuel selection, organic matter containing carboxyl functional groups (such as formic acid) can form Ti-OOH bonds with the surface of the photoanode, accelerate the transfer of electrons to the cathode, and achieve the highest short-circuit current density (3.2mA / cm 2 ) and open circuit voltage (0.78V). For actual organic wastewater (COD≈3000mg / L), the battery still maintains 1.5mA / cm after 15 days of continuous operation. 2 Stable current output demonstrates its efficient degradation and energy conversion capabilities for organic matter in complex wastewater. This technology overcomes the light absorption limitations of traditional TiO2 photoanodes and provides an environmentally friendly and economically efficient solution for the resource-based treatment of carboxylic acid-containing organic wastewater.

[0014] In a specific embodiment of the first aspect, the TiO2 substrate is prepared by an anodic oxidation method, and a vertically oriented nanotube array structure is formed on the surface of the TiO2 substrate.

[0015] In a specific embodiment of the first aspect, in the 6CdS / TiO2 composite photoanode, the particle size of the CdS quantum dots is 2-5 nm, and the conduction band energy level thereof forms a heterojunction structure with the valence band of TiO2.

[0016] In a specific embodiment of the first aspect, when the fuel is formic acid, its concentration range is 20 mM to 200 mM, and the photocurrent density shows a saturation trend as the concentration increases.

[0017] In a specific embodiment of the first aspect, when the fuel is actual organic wastewater, the COD concentration of the wastewater is 3000 mg / L, and the photocurrent density of the battery is stabilized at 1.5 mA / cm after continuous operation for 15 days. 2 above.

[0018] In a specific embodiment of the first aspect, the ion exchange membrane is a proton exchange membrane (PEM) or an anion exchange membrane (AEM) for selectively transporting photogenerated charge carriers.

[0019] In a specific embodiment of the first aspect, the open circuit voltage and short circuit current of the photocatalytic fuel cell are optimized by:

[0020] The carboxyl functional groups on the surface of the photoanode form Ti-OOH bonds with the metal oxide;

[0021] The adsorption kinetics of fuel molecules on the photoanode surface are limited by the saturation adsorption effect at a concentration of 20 M.

[0022] Secondly, the application of photocatalytic fuel cells based on cadmium sulfide-titanium dioxide composite photoanodes in the treatment of organic wastewater, which includes but is not limited to industrial wastewater, domestic sewage or mixed wastewater containing urea and glucose. During the treatment process, photogenerated power output and organic matter degradation are achieved simultaneously.

[0023] In a specific embodiment of the second aspect, the photoelectric conversion efficiency of the photocatalytic fuel cell is optimized by the following parameters:

[0024] the number of CdS quantum dot layers in the photoanode;

[0025] Fuel molecule functional group type;

[0026] The cell operates in the potential range of 0.5 V to 1.23 V (vs. RHE).

[0027] In a specific embodiment of the second aspect, the photoelectric conversion efficiency reaches a maximum value when formic acid is used as fuel, and its short-circuit current density is 3.2 mA / cm 2 , the open circuit voltage is 0.78V.

[0028] The beneficial effects of the present invention are:

[0029] 1. This invention overcomes the photoresponse limitations of traditional TiO2 by constructing a CdS / TiO2 heterojunction photoanode. Precise control of the number of quantum dot layers and particle size optimizes the visible light absorption range and enhances interfacial charge separation. The carboxyl functional group fuel forms a directional bond on the electrode surface, significantly accelerating directional electron migration and achieving a significant increase in photoelectric conversion efficiency. This design fundamentally addresses the dual drawbacks of low photogenerated electron utilization and poor fuel adaptability.

[0030] 2. In organic wastewater treatment scenarios, the system's dual functionality of simultaneously outputting electricity and degrading pollutants significantly reduces energy consumption. Its broad adaptability to complex wastewater compositions (such as acid / alcohol / sugar mixtures) and long-term operational stability overcome bottlenecks in the engineering application of existing technologies. This technology provides an innovative path for industrial wastewater resource utilization that combines environmental benefits with energy recovery. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic diagram of the photocurrent-voltage curve of the present invention that varies with the number of CdS layers.

[0032] Figure 2 Schematic diagrams of (a) photocurrent changing with formic acid concentration, (b) photocurrent comparison of different organic substances at different concentrations, and (c) photocatalytic fuel cell performance comparison of different organic substances according to the present invention.

[0033] Figure 3 It is a schematic diagram of the change of the photocurrent of the photocatalytic fuel cell of the present invention with the test time. DETAILED DESCRIPTION

[0034] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0035] like Figures 1 to 3 The photocatalytic fuel cell based on cadmium sulfide titanium dioxide composite photoanode and its application are shown.

[0036] The TiO2 electrode in this application is prepared by an anodic oxidation method. The CdS / TiO2 is prepared primarily using a continuous ion deposition method. The prepared TiO2 electrode is first placed in a cadmium nitrate solution for one minute, then rinsed in clean water, and then placed in a sodium sulfide solution for one minute. This forms a layer of CdS quantum dots on its surface. Repeating this process creates a multilayer of CdS quantum dots. The prepared CdS / TiO2 is used as a photoanode, with Pt as the cathode, separated by an ion exchange membrane, to create a photocatalytic fuel cell.

[0037] Results and Discussion

[0038] Preparation and Analysis of CdS / TiO2 Photoanode

[0039] Figure 1 The photoelectrochemical water splitting efficiency was compared after depositing different numbers of CdS layers. The results show that when the number of CdS layers is increased to 6, the photocurrent gradually increases. Further increases lead to a gradual decrease in the photocurrent. This is primarily due to the fact that with further CdS deposition, the quantum dot size increases, the conduction band energy level decreases, and the photoelectron injection efficiency decreases. Therefore, this experiment selected TiO2 deposited with 6 layers of CdS (i.e., 6CdS / TiO2) as the photoanode for further experiments.

[0040] Performance comparison of photocatalytic fuel cells

[0041] A photocatalytic fuel cell device constructed with 6CdS / TiO2, in which a Pt sheet electrode is selected as the cathode. Figure 2 a Comparison of the photocurrent response after adding different concentrations of formic acid. As the formic acid concentration increases to 200 mM, the photocurrent density gradually increases. When the formic acid concentration is further increased to 300 mM, the photocurrent density no longer increases. This is mainly because formic acid has reached saturated adsorption on the active sites on the photoanode surface. Figure 2 b compares the photocurrents of formic acid, methanol, urea and glucose at different concentrations (potential at 1.23 V). It can be seen that when the concentration of organic matter increases to 20 M, the photocurrents of all organic matter reach saturation values, and the photocatalytic degradation reaction kinetics are completely limited by the adsorption process of organic matter on the electrode surface. Figure 2 c compares the effects of different organic substrates at a concentration of 20 M on the performance of the photocatalytic fuel cell. Formic acid exhibits the highest open-circuit voltage and short-circuit current, followed by methanol, glucose, and urea. This is primarily due to the carboxyl groups on the formic acid surface being able to better bond with metals to form Ti-OOH bonds, enhancing the rate of electron transfer to the cathode.

[0042] Study on the stability of photocatalytic fuel cells

[0043] After comparing the effects of different organic substrates on photocatalytic fuel cells, we further analyzed the actual organic water samples used as substrates. The water samples came from an organic wastewater treatment plant of our company, and the COD concentration was about 3000 mg / L. Figure 3 The stability of the photocatalytic fuel cell constructed with 6CdS / TiO2 was tested. After 15 days of continuous operation, the current density of the photocatalytic fuel cell remained stable (about 1.5mA / cm2).

[0044] This application uses CdS quantum dots to improve the photoresponse characteristics of TiO2 and utilizes them as photoanodes in photocatalytic fuel cells. The authors compared the effects of different organic substrates on the photocatalytic fuel cell, finding that acidic organics exhibited higher photocurrent density and cell power. The CdS / TiO2-based photocatalytic fuel cell maintained stable operation when using actual wastewater as the organic substrate. This research advances the industrialization of photocatalytic fuel cells.

[0045] Example 1: Preparation of 6CdS / TiO2 composite photoanode

[0046] TiO2 substrate preparation:

[0047] Anodic oxidation was used, with a pure titanium sheet (purity ≥ 99.7%, thickness 0.25 mm) as the anode and a platinum sheet as the cathode. The samples were placed in an ethylene glycol electrolyte containing 0.5 wt% NH4F and oxidized at 60 V for 2 hours to form vertically oriented TiO2 nanotube arrays.

[0048] The oxidized titanium sheet was rinsed with deionized water and annealed in a muffle furnace at 450°C for 2 hours to obtain anatase TiO2 photoanode.

[0049] CdS quantum dot deposition:

[0050] Prepare 0.1M cadmium nitrate (Cd(NO3)2·4H2O) aqueous solution and 0.1M sodium sulfide (Na2S·9H2O) aqueous solution;

[0051] The TiO2 electrode was immersed in cadmium nitrate solution for 1 minute, rinsed with deionized water for 30 seconds, and then immersed in sodium sulfide solution for 1 minute to form a single layer of CdS quantum dots;

[0052] The above steps were repeated 6 times to obtain a 6CdS / TiO2 composite photoanode (total deposition time: 12 minutes). The particle size of each layer of CdS quantum dots was characterized by transmission electron microscopy (TEM) to be 2-5 nm.

[0053] Example 2: Photocatalytic fuel cell assembly

[0054] Battery structure:

[0055] 6CdS / TiO2 was used as the photoanode, a platinum sheet (2 cm × 2 cm) was used as the cathode, the cathode and the photoanode were separated by a Nafion 117 proton exchange membrane.

[0056] The fuel chamber and the cathode chamber are respectively injected with organic wastewater and 0.5M sodium sulfate electrolyte.

[0057] Lighting conditions:

[0058] A 300W xenon lamp (AM 1.5 filter) was used to simulate sunlight, with a light intensity of 100mW / cm 2 , the effective irradiation area of ​​the photoanode is 4cm 2 .

[0059] Example 3: Performance test of different organic fuels

[0060] Fuel solution preparation:

[0061] Formic acid (HCOOH), methanol (CH2OH), urea (CO(NH2)2), glucose (C6H 12 O6) were dissolved in deionized water to prepare solutions with a concentration gradient of 10mM, 50mM, 100mM, 200mM, and 300mM.

[0062] Test method:

[0063] The photocurrent density was measured in a constant potential mode at 1.23 V (vs. RHE) on an electrochemical workstation (CHI 760E).

[0064] Record the photocurrent variation curve over time and calculate the saturation photocurrent value (J_sat).

[0065] Experimental results:

[0066] Formic acid reaches a maximum J_sat = 3.2 mA / cm at a concentration of 200 mM 2 , further increasing the concentration to 300 mM, J_sat had no significant change;

[0067] The J_sat of methanol, glucose and urea at 200mM concentration is 2.6mA / cm 2 , 1.8mA / cm 2 , 1.2mA / cm 2 ;

[0068] When carboxyl functional groups are present (formic acid), the open circuit voltage (Voc) increases to 0.78 V and the short circuit current (Jsc) is 3.1 mA / cm 2 , better than other fuels (Voc≤0.65V, Jsc≤2.5mA / cm 2 ).

[0069] Example 4: Actual organic wastewater treatment stability test

[0070] Wastewater sources:

[0071] The sample was taken from the regulating tank of a wastewater treatment plant in a chemical park. The COD concentration was diluted to 3000 mg / L and the pH was adjusted to 5.0.

[0072] Long-running tests:

[0073] In continuous flow mode, wastewater was pumped into the fuel chamber at a flow rate of 10 mL / min, and the effluent COD value was measured daily;

[0074] After 15 days of operation, the photocurrent density stabilized at 1.5 mA / cm 2 , COD removal rate was maintained at 85%±3%.

[0075] Example 5: Battery Performance Optimization Verification

[0076] CdS layer number optimization:

[0077] Compared with the photoanode deposited with 1-8 layers of CdS, the photocurrent density of 6-layer CdS / TiO2 under AM 1.5 light is 3.0mA / cm 2 , significantly higher than pure TiO2 (1.3mA / cm 2 ) and 8 layers of CdS / TiO2 (2.2mA / cm 2 ).

[0078] Potential window optimization:

[0079] In the range of 0.5V to 1.23V (vs. RHE), the battery power density increases first and then decreases with the increase of potential, and the optimal operating point is at 1.0V (power density = 1.2mW / cm 2 ).

[0080] Technical effect verification:

[0081] It can be seen from the above embodiments that the technical solution of the present invention achieves breakthroughs in the following aspects:

[0082] Improved photoelectric conversion efficiency: The photocurrent of the 6CdS / TiO2 photoanode is 138% higher than that of pure TiO2, attributed to the quantum dot sensitization effect and charge separation at the heterojunction interface;

[0083] Enhanced fuel selectivity: Carboxyl functional groups enhance electron transport through chemical adsorption, making formic acid fuel cells perform better than traditional alcohols / sugars;

[0084] Industrial adaptability optimization: In actual wastewater treatment, the battery operated continuously for 15 days without performance degradation, and the COD removal rate met the third-level standard of the "Integrated Wastewater Discharge Standard" (GB 8978-1996).

[0085] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A photocatalytic fuel cell based on a cadmium sulfide titanium dioxide composite photoanode, characterized in that: include: Photoanode: It consists of a TiO2 substrate and a CdS quantum dot layer deposited on its surface. The CdS quantum dot layer is prepared by continuous ion deposition. The specific steps are as follows: The TiO2 electrode was immersed in cadmium nitrate solution and sodium sulfide solution for 1 minute each to form a single layer of CdS quantum dots; Repeat the above deposition steps until the number of CdS layers is 6 to obtain a 6CdS / TiO2 composite photoanode; Cathode: platinum (Pt) electrode; Isolation component: The cathode and photoanode are isolated by an ion exchange membrane; Fuel supply system: using organic matter containing carboxyl functional groups as fuel, the organic matter includes at least one of formic acid, methanol, and glucose.

2. The photocatalytic fuel cell based on the cadmium sulfide-titanium dioxide composite photoanode according to claim 1, characterized in that: The TiO2 substrate is prepared by an anodic oxidation method, and a vertically oriented nanotube array structure is formed on the surface of the TiO2 substrate.

3. The photocatalytic fuel cell based on the cadmium sulfide-titanium dioxide composite photoanode according to claim 1, characterized in that: In the 6CdS / TiO2 composite photoanode, the particle size of the CdS quantum dots is 2-5 nm, and the conduction band energy level thereof forms a heterojunction structure with the valence band of TiO2.

4. The photocatalytic fuel cell based on the cadmium sulfide-titanium dioxide composite photoanode according to claim 1, characterized in that: When the fuel is formic acid, its concentration ranges from 20 mM to 200 mM, and the photocurrent density shows a saturation trend as the concentration increases.

5. The photocatalytic fuel cell based on the cadmium sulfide-titanium dioxide composite photoanode according to claim 1, characterized in that: When the fuel is actual organic wastewater with a COD concentration of 3000 mg / L, the photocurrent density stabilizes at 1.5 mA / cm after the battery is operated continuously for 15 days. 2 above.

6. The photocatalytic fuel cell based on the cadmium sulfide-titanium dioxide composite photoanode according to claim 1, characterized in that: The ion exchange membrane is a proton exchange membrane (PEM) or an anion exchange membrane (AEM), which is used to selectively transport photogenerated charge carriers.

7. The photocatalytic fuel cell based on the cadmium sulfide-titanium dioxide composite photoanode according to claim 1, characterized in that: The open circuit voltage and short circuit current of the photocatalytic fuel cell are optimized by: The carboxyl functional groups on the surface of the photoanode form Ti-OOH bonds with the metal oxide; The adsorption kinetics of fuel molecules on the photoanode surface are limited by the saturation adsorption effect at a concentration of 20 M.

8. Application of photocatalytic fuel cells based on cadmium sulfide-titanium dioxide composite photoanodes in the treatment of organic wastewater, characterized by: The organic wastewater includes but is not limited to industrial wastewater, domestic sewage or mixed wastewater containing urea and glucose, and the output of photoelectric energy and the degradation of organic matter are simultaneously achieved during the treatment process.

9. The use of a photocatalytic fuel cell based on a cadmium sulfide-titanium dioxide composite photoanode in the treatment of organic wastewater according to claim 8, characterized in that: The photoelectric conversion efficiency of the photocatalytic fuel cell is optimized by the following parameters: the number of CdS quantum dot layers in the photoanode; Fuel molecule functional group type; The cell operates in the potential range of 0.5 V to 1.23 V (vs. RHE).

10. The use of a photocatalytic fuel cell based on a cadmium sulfide-titanium dioxide composite photoanode in the treatment of organic wastewater according to claim 1, characterized in that: The photoelectric conversion efficiency reaches its maximum when formic acid is used as fuel, and its short-circuit current density is 3.2 mA / cm 2 , the open circuit voltage is 0.78V.

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