Method for producing hydrogen by photoelectrocatalytic pollution treatment of municipal sewage

Abstract

This invention belongs to the field of photoelectrocatalytic pollution treatment and hydrogen production technology, and particularly relates to a method for photoelectrocatalytic pollution treatment and hydrogen production from urban wastewater. The method involves pretreating urban wastewater using an ultrafiltration membrane module to remove suspended solids and large organic molecules. The ultrafiltration membrane has a pore size of 0.1-1 μm, is made of polyethersulfone, has a molecular weight cutoff of 10 kDa, and is pretreated at a pressure of 0.1-0.2 MPa. A BiVO4-modified WO3 nanorod array photoanode and a Cu2O-supported Pt nanoparticle cathode are prepared, with a Bi:W molar ratio of 1:5 in the photoanode and a Pt mass percentage of 2% in the cathode. The pretreated urban wastewater is then fed into the photoelectrocatalytic unit of a single-chamber reactor, with an external bias voltage of 0.5-1.5V applied, and 0.05-0.2 g / L TiO2-g-C3N4 composite photosensitizer added. The reaction temperature is controlled at 20-35℃, the stirring rate at 100-200 rpm, and the reaction is carried out at a 300-800 nm wavelength and a stirring speed of 50-100 mW / cm². 2 The reaction occurs under light intensity; after the reaction, the water is left in a sedimentation tank for 30-60 minutes to separate suspended solids before being discharged, and hydrogen is collected through a polytetrafluoroethylene membrane separator.

Description

Technical Field

[0001] This invention belongs to the field of photoelectrocatalytic pollution treatment and hydrogen production technology, and particularly relates to a method for using photoelectrocatalytic pollution treatment and hydrogen production from urban sewage. Background Technology

[0002] Currently, urban wastewater treatment and hydrogen production are mostly independent processes. Traditional wastewater treatment technologies require complex pretreatment stages to handle high-COD wastewater, and are characterized by high energy consumption and low resource recovery rates. Hydrogen production relies on fossil fuel reforming or high-purity water electrolysis, which suffers from high costs and large carbon emissions. While photoelectrocatalysis technology offers the possibility of integrated wastewater treatment and hydrogen production, existing solutions mostly use single TiO2-based catalysts, which have a photoresponse range limited to ultraviolet light, high electron-hole recombination rates, and rely on noble metal catalysts to lower the reaction energy barrier. This results in insufficient photoelectric conversion efficiency and high operating costs, making it difficult to meet the dual requirements of efficient wastewater treatment and low-cost hydrogen production in practical applications.

[0003] Existing technologies still suffer from problems such as poor catalyst loading stability and insufficient process adaptability. Some solutions can only treat low-COD wastewater and require significant additional energy investment for pretreatment, limiting their large-scale application. Furthermore, flaws such as unreasonable photoelectrode structure design and weak synergistic effects between photosensitizers and catalysts further restrict the improvement of COD removal rates and hydrogen yields, failing to achieve efficient synergy between wastewater treatment and energy production. Therefore, there is an urgent need to develop a photoelectrocatalytic technology solution that combines broad spectral response, low energy consumption, and high stability. Summary of the Invention

[0004] The purpose of this invention is to address the aforementioned technical problems by providing a method for hydrogen production through photoelectrocatalytic treatment of urban wastewater, comprising the following steps:

[0005] Step 1: Pre-treat urban sewage through an ultrafiltration membrane module to remove suspended solids and macromolecular organic matter. The ultrafiltration membrane has a pore size of 0.1-1μm, is made of polyethersulfone, has a molecular weight cutoff of 10kDa, and a pretreatment pressure of 0.1-0.2MPa.

[0006] Step 2: Prepare a BiVO4-modified WO3 nanorod array photoanode and a Cu2O-supported Pt nanoparticle cathode, respectively. The Bi:W molar ratio in the photoanode is 1:5, and the Pt mass percentage in the cathode is 2%.

[0007] Step 3: The pretreated urban wastewater is fed into the photoelectrocatalytic unit of a single-chamber reactor. An external bias voltage of 0.5-1.5V is applied, and 0.05-0.2g / LTiO2-g-C3N4 composite photosensitizer is added. The reaction temperature is controlled at 20-35℃, the stirring speed at 100-200rpm, and the reaction is carried out at a 300-800nm ​​wavelength and a stirring speed of 50-100mW / cm². 2 Reaction under light intensity;

[0008] Step 4: After the reaction, the water is left in a sedimentation tank for 30-60 minutes to separate suspended solids before being discharged. Hydrogen is then collected through a polytetrafluoroethylene membrane separator.

[0009] Preferably, the Ti:C molar ratio of the TiO2-g-C3N4 composite photosensitizer is 1:3, and it is prepared by mixing urea with TiO2 nanoparticles and calcining at 550°C under a nitrogen atmosphere for 4 hours.

[0010] Preferably, the WO3 nanorod array of the photoanode is 1-2 μm long and 50-100 nm in diameter, prepared by hydrothermal method, with a WO3 precursor concentration of 0.1 mol / L and a BiVO4 deposition time of 2 h.

[0011] Preferably, the Pt nanoparticles in the cathode have a size of 5-10 nm and are prepared by electrodeposition with an electrodeposition current density of 5 mA / cm². 2 Time: 30 minutes.

[0012] Preferably, the pH of the electrolyte in the photoelectrocatalytic reaction is controlled at 6.0-8.0, and the initial COD of the treated urban sewage is 200-600 mg / L and the conductivity is 5-10 mS / cm.

[0013] Preferably, the illumination is provided by a condenser lens and a 150W xenon lamp, with the condenser lens having a focal length of 20cm and a focusing ratio of 5:1, and the xenon lamp simulating the AM1.5G spectrum with an ultraviolet content of 5%.

[0014] Preferably, the single-chamber reactor has a volume of 1-5L and is equipped with a transparent quartz window. The photoelectrocatalytic unit also includes a DC power supply, a light intensity meter, and a pH / temperature probe.

[0015] Preferably, the PTFE membrane separator used for hydrogen collection has a pore size of 0.02 μm and a separation efficiency of >97%, and the collected hydrogen is stored in a hydrogen storage tank with a pressure of 0.1-0.5 MPa.

[0016] In view of this, the present invention provides a photoelectrocatalytic method for treating pollution and producing hydrogen based on illumination-adaptive planar representation.

[0017] The beneficial effects of this invention are:

[0018] This invention provides a photoelectrocatalytic method and system for hydrogen production from wastewater based on illumination-adaptive planar representation, aiming to achieve integrated and synergistic development of urban wastewater treatment and hydrogen production. This method optimizes the photoelectrode structure, composite photosensitizers, and regulates reaction conditions, leveraging solar energy to drive the photoelectrocatalytic reaction. This efficiently produces hydrogen while degrading pollutants in wastewater, solving problems such as complex wastewater pretreatment, high catalyst costs, and low energy utilization in traditional technologies.

[0019] Its core solution includes wastewater pretreatment, photoelectrocatalytic reaction, and product separation. A composite catalyst-modified photoelectrode is prepared using a specific process, paired with a dedicated photosensitizer, to achieve a synergistic effect of photo-electro-catalysis under suitable reaction parameters. The system consists of a pretreatment unit, a photoelectrocatalytic unit, a light source system, a control system, and a gas collection unit. These units operate collaboratively, allowing for direct treatment of urban wastewater without complex pretreatment procedures. While ensuring efficient pollutant removal, it also stably produces hydrogen energy, combining environmental benefits with energy value. Attached Figure Description

[0020] Figure 1 This is a process flow diagram of the present invention;

[0021] Figure 2 This is a graph showing the relationship between hydrogen yield and light intensity in this invention. Detailed Implementation

[0022] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0023] The purpose of this invention is to provide a photoelectrolyte-based electrolyzer catalyst formulation and process package. By optimizing the photoelectrode structure, composite photosensitizer, and reaction conditions, it utilizes solar energy to achieve efficient COD degradation and hydrogen production in urban wastewater, solving the problems of high COD wastewater pretreatment requirements and high cost of precious metal catalysts in traditional technologies.

[0024] Catalyst formulation:

[0025] Anode catalyst:

[0026] Composition: TiO2-Fe2O3, with Fe2O3 accounting for 10-15% by mass (optimal 12.5%).

[0027] Structure: TiO2 nanorods (length 200-300nm, diameter 20-30nm, hexagonal crystal system), with Fe2O3 particles (particle size 10-15nm, cubic crystal system) on the surface.

[0028] Performance: Loading capacity 1.5-2.0 mg / cm³ 2 (Average 1.8 mg / cm) 2 ), specific surface area 120-150m² 2 / g, photoresponse range 400-600nm (UV-Vis detection), OER overpotential 280-300mV@10mA / cm².

[0029] Carrier: Carbon fiber cloth (thickness 0.3mm, specific surface area 200-300m² / g, conductivity >10³S / cm).

[0030] Cathode catalyst: Composition: TiO2-CuS, CuS mass percentage 15-20% (optimal 18%).

[0031] Structure: TiO2 nanorod substrate, CuS forming a heterojunction (particles 5-10 nm, monoclinic crystal system).

[0032] Performance: Loading capacity 1.5-2.0 mg / cm² (average 1.8 mg / cm²), specific surface area 130-160 m² / g, HER overpotential 120-140 mV @ 10 mA / cm².

[0033] Carrier: Same as anode.

[0034] Design principle: TiO2 acts as a photosensitive matrix to absorb ultraviolet light and generate electron-hole pairs, Fe2O3 extends the visible light response and catalyzes the decomposition of organic matter by OER, and CuS improves electron transfer efficiency and promotes HER hydrogen production.

[0035] Step 1: Hydrothermal growth of TiO2 nanorods: Prepare a 0.05 mol / L TiCl4 (purity >99%) ethanol solution (50 mL), add 5 mL of deionized water (conductivity <0.1 μS / cm), immerse carbon fiber cloth (5 cm × 5 cm) in the solution, hydrothermally grow at 150℃ for 6 h (autoclave, pressure 1-1.5 MPa), and dry at 120℃ for 4 h (vacuum degree 0.01 MPa).

[0036] Step 2: Fe2O3 chemical deposition (anodide): Prepare a 0.02mol / LFe(NO3)3·9H2O solution (50mL, purity >99%), immerse TiO2 / carbon fiber cloth in it, stir at 80℃ for 2h (500rpm), and calcine in air at 400℃ for 2h (heating rate 5℃ / min).

[0037] Step 3: CuS ion exchange (cathode): TiO2 / carbon fiber cloth is immersed in 0.03 mol / L CuSO4 solution (50 mL, purity >99%), 0.1 mol / L Na2S (purity >98%) is added, reacted at 60℃ for 1 h, and dried at 80℃ for 4 h (vacuum degree 0.01 MPa).

[0038] Process features: Hydrothermal method ensures uniform growth of TiO2 nanorods, and chemical deposition and ion exchange precisely control the loading of Fe2O3 and CuS.

[0039] Application conditions: Electrolyzer: PEM electrolyzer (single cell capacity 10L, electrode area 200cm²), anode flows through municipal sewage (COD 200-600mg / L, conductivity 5-10mS / cm), cathode flows through pure water (flow rate 0.5L / h).

[0040] Parameters: Voltage: 1.8-2.3V, Current density: 0.6-1.5A / cm².

[0041] Temperature: 35-55℃, UV lamp: 365nm, 10W / cm².

[0042] Membrane: Nafion 117 (thickness 175 μm, IEC 0.9 meq / g).

[0043] Performance: H2 yield: 1.6-2.0 L / min (purity >99.9%).

[0044] COD removal rate: 88-92% (ultraviolet spectrophotometry).

[0045] Lifespan: >1000 hours (attenuation <8%).

[0046] TiO2 nanorods absorb ultraviolet light to generate electron-hole pairs, while Fe2O3 extends the photoresponse to the visible light range (band gap decreases from 3.2 eV to 2.1 eV, UV-Vis detection), enhancing the ability of photogenerated holes to oxidize COD. CuS forms a heterojunction (interfacial barrier of approximately 0.5 eV), accelerating electron transfer to the cathode for hydrogen production. Compared with CN114057408A (single-phase TiO2, band gap 3.2 eV) and J.Am.Chem.Soc. (TiO2-Fe2O3, without CuS), the ternary system synergistically improves photoelectric efficiency by 20-25%.

[0047] Process optimization: The aspect ratio of TiO2 nanorods was controlled using a hydrothermal method (10:1, SEM detection), Fe2O3 was uniformly distributed (10-15 nm thickness) by chemical deposition, and CuS heterojunctions were prepared by ion exchange (coverage >90%). Compared with CN112852007A (simple coating, uniformity <80%), this process improves catalyst loading stability and photoelectric synergy, and reduces electron-hole recombination rate by 30% (photocurrent test).

[0048] Integrated wastewater treatment and hydrogen production: Directly treats wastewater with COD of 200-600 mg / L, with an H2 production rate of 1.6-2.0 L / min and a COD removal rate of 88-92%, superior to Nature Energy (NiMo, COD <100 mg / L, H2 <1.0 L / min). Photovoltaic-electric synergistic decomposition of organic matter and hydrogen production require no pretreatment, saving approximately 2 kWh / m³ of energy compared to CN112852007A. 3 .

[0049] Urban sewage is introduced into the device and pretreated by an ultrafiltration membrane (pore size 0.1-1μm, polyethersulfone material, molecular weight cutoff 10kDa) to remove suspended solids and large molecular organic matter;

[0050] In the photoelectrocatalytic unit, the photoanode is exposed to sunlight (spectral range 300-800 nm, light intensity 50-100 mW / cm²). 2 Under irradiation, organic matter is oxidized, and hydrogen gas is generated by the reduction of water by photogenerated electrons at the cathode.

[0051] Apply an external bias voltage of 0.5-1.5V (preferably 1.0V), add 0.05-0.2g / LTiO2-g-C3N4 composite photosensitizer (Ti:C molar ratio 1:3) to the electrolyte, and control the pH at 6.0-8.0;

[0052] The reaction temperature was maintained at 20-35℃, and the stirring speed was 100-200 rpm to ensure uniform dispersion of the photosensitizer and gas release.

[0053] After treatment, the water is discharged after suspended solids are separated in a sedimentation tank (retention time 30-60 min), and hydrogen is collected through a polytetrafluoroethylene membrane separator (pore size 0.02 μm).

[0054] Pretreatment unit: ultrafiltration membrane module (effective area 0.5m², pressure 0.1-0.2MPa), equipped with sedimentation tank (volume 50-100L);

[0055] Photoelectrocatalytic unit: single-chamber reactor (volume 1-5L, transparent quartz window), photoanode is BiVO4 modified WO3 nanorod array (rod length 1-2μm, diameter 50-100nm, Bi:W molar ratio 1:5), cathode is Cu2O supported Pt nanoparticles (particle size 5-10nm, Pt mass percentage 2%).

[0056] Light source system: condenser lens (focal length 20cm, focusing ratio 5:1) and 150W xenon lamp (simulating AM1.5G spectrum, ultraviolet content 5%).

[0057] Control system: Equipped with DC power supply (0-5V adjustable), light intensity meter and pH / temperature probe;

[0058] Gas collection unit: membrane separator (separation efficiency >97%) and hydrogen storage tank (pressure 0.1-0.5MPa).

[0059] Example 1: Laboratory Validation;

[0060] One liter of wastewater from a primary sedimentation tank in the city was collected. The COD was 350 mg / L, TOC was 120 mg / L, and pH was 7.2. After pretreatment with an ultrafiltration membrane (0.2 μm pore size, 0.15 MPa pressure), the COD was reduced to 280 mg / L. The mixture was placed in a photoelectrocatalytic unit. The photoanode was BiVO4-WO3 nanorods (prepared via hydrothermal method: 0.1 mol / L WO3 precursor, BiVO4 deposition time 2 h), and the cathode was Cu2O-Pt (electrodeposition of Pt, current density 5 mA / cm², time 30 min). The illumination intensity was 90 mW / cm², the bias voltage was 1.0 V, and 0.15 g / L TiO2-g-C3N4 (prepared via thermal polymerization, calcination temperature 550 °C) was added. The mixture was stirred at 150 rpm and reacted for 45 minutes. Results: COD decreased to 28 mg / L (removal rate 92%), hydrogen production rate was 15 mL / min (purity 98.5%), and photocurrent density was 3.2 mA / cm².

[0061] Example 2: Outdoor pilot test;

[0062] Wastewater from a wastewater treatment plant, with a flow rate of 2000 m³ / d, has a COD of 400 mg / L and a pH of 6.5. After pretreatment, the COD is reduced to 320 mg / L. The treated wastewater then enters a 5 m³ photoelectrocatalytic unit under natural sunlight (average 80 mW / cm²), a bias voltage of 1.2 V, a photosensitizer concentration of 0.2 g / L, a temperature of 25 °C, and stirring at 200 rpm. After treatment, the COD is reduced to 35 mg / L (removal rate 91%), the hydrogen production rate reaches 1.8 m³ / h, the energy consumption is 0.78 kWh / m³ of water, and the hydrogen produced can power a 10 kW fuel cell for 2 hours.

[0063] Example 3: Stability of photoelectrode and photosensitizer;

[0064] The experiment was conducted for 500 hours in simulated wastewater (COD 300 mg / L, pH 7.0) under an illumination of 70 mW / cm² and a bias voltage of 1.0 V. The photocurrent attenuation of the BiVO4-WO3 photoanode was only 7%, the activity of the Cu2O-Pt cathode decreased by 5%, and the activity of the TiO2-g-C3N4 photosensitizer remained at 95% after 10 cycles, which is superior to that of traditional TiO2 (which attenuated by 20%).

[0065] Example 4: Preparation and optimization of photosensitizer;

[0066] TiO2-g-C3N4 was prepared by mixing urea (10g) and TiO2 nanoparticles (0.5g) and calcining at 550℃ under a nitrogen atmosphere for 4h. When the optimized Ti:C ratio was 1:3, the specific surface area reached 120m² / g, and the light absorption edge red-shifted to 520nm, significantly improving the photocatalytic efficiency.

[0067] The embodiments of this application have been described above with reference to the accompanying drawings. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. This application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A photoelectrochemical hydrogen production method for pollution control based on illumination-adaptive planar representation, characterized in that: Includes the following steps: Step 1: Pre-treat urban sewage through an ultrafiltration membrane module to remove suspended solids and macromolecular organic matter. The ultrafiltration membrane has a pore size of 0.1-1μm, is made of polyethersulfone, has a molecular weight cutoff of 10kDa, and a pretreatment pressure of 0.1-0.2MPa. Step 2: Prepare a BiVO4-modified WO3 nanorod array photoanode and a Cu2O-supported Pt nanoparticle cathode, respectively. The Bi:W molar ratio in the photoanode is 1:5, and the Pt mass percentage in the cathode is 2%. Step 3: The pretreated urban wastewater is fed into the photoelectrocatalytic unit of a single-chamber reactor. An external bias voltage of 0.5-1.5V is applied, and 0.05-0.2g / LTiO2-g-C3N4 composite photosensitizer is added. The reaction temperature is controlled at 20-35℃, the stirring speed at 100-200rpm, and the reaction is carried out at a 300-800nm ​​wavelength and a stirring speed of 50-100mW / cm². 2 Reaction under light intensity; Step 4: After the reaction, the water is left in a sedimentation tank for 30-60 minutes to separate suspended solids before being discharged. Hydrogen is then collected through a polytetrafluoroethylene membrane separator.

2. The photoelectrochemical hydrogen production method for pollution control based on illumination-adaptive planar representation according to claim 1, characterized in that: The TiO2-g-C3N4 composite photosensitizer has a Ti:C molar ratio of 1:3 and is prepared by mixing urea with TiO2 nanoparticles and calcining at 550°C under a nitrogen atmosphere for 4 hours.

3. The photoelectrochemical hydrogen production method for pollution control based on illumination-adaptive planar representation according to claim 1, characterized in that: The WO3 nanorod array of the photoanode is 1-2 μm long and 50-100 nm in diameter. It is prepared by hydrothermal method with a WO3 precursor concentration of 0.1 mol / L and a BiVO4 deposition time of 2 h.

4. The photoelectrochemical hydrogen production method for pollution control based on illumination-adaptive planar representation according to claim 1, characterized in that: The cathode contains Pt nanoparticles with a size of 5-10 nm, prepared by electrodeposition at a current density of 5 mA / cm². 2 Time: 30 minutes.

5. The photoelectrochemical hydrogen production method for pollution control based on illumination-adaptive planar representation according to claim 1, characterized in that: The electrolyte pH of the photoelectrocatalytic reaction is controlled at 6.0-8.0, and the initial COD of the treated urban sewage is 200-600 mg / L, and the conductivity is 5-10 mS / cm.

6. The photoelectrochemical hydrogen production method for pollution control based on illumination-adaptive planar representation according to claim 1, characterized in that: The illumination is provided by a condenser lens and a 150W xenon lamp. The condenser lens has a focal length of 20cm and a light concentration ratio of 5:

1. The xenon lamp simulates the AM1.5G spectrum with an ultraviolet content of 5%.

7. The photoelectrochemical hydrogen production method for pollution control based on illumination-adaptive planar representation according to claim 1, characterized in that: The single-chamber reactor has a volume of 1-5L and is equipped with a transparent quartz window. The photoelectrocatalytic unit also includes a DC power supply, a light intensity meter, and a pH / temperature probe.

8. The photoelectrochemical hydrogen production method for pollution control based on illumination-adaptive planar representation according to claim 1, characterized in that: The hydrogen collection uses a polytetrafluoroethylene membrane separator with a pore size of 0.02 μm and a separation efficiency of >97%. The collected hydrogen is stored in a hydrogen storage tank with a pressure of 0.1-0.5 MPa.

Images