Method and device for continuously and fully electrolyzing seawater by a photothermal and electrocatalytic bifunctional composite nanocarbon film

Abstract

The present invention relates to the field of renewable clean energy, and specifically to a method and device for continuously and fully electrolyzing seawater using a dual-functional composite nano-carbon film with photothermal and electrocatalytic properties. This method utilizes a composite nano-carbon film with high photothermal conversion efficiency and high electrocatalytic activity for water electrolysis to absorb sunlight, generate heat to evaporate seawater to produce fresh water, and at the same time uses this film as the cathode for water electrolysis. An electrolytic cell with a communicating vessel is designed to introduce an electrolyte solution, and after illumination and power-on, continuous seawater desalination-full electrolysis is achieved. That is, a physical deposition / wet chemical synthesis method is used to support electrocatalytically active nanoparticles / nanowires on a porous nano-carbon material film to construct a composite film. An absorbent material such as bacterial cellulose is laid flat under the film and placed on a heat-insulating carrier, and the other end of the bacterial cellulose is immersed in seawater to make it a water channel connecting seawater and the composite film. This composite film can achieve continuous desalination and electrolysis of seawater, and efficiently obtain clean energy hydrogen under low carbon emissions.

Description

Technical Field

[0001] The present invention relates to the field of renewable clean energy, and specifically to a method and device for continuously and fully electrolyzing seawater using a dual-functional composite nano-carbon film with photothermal and electrocatalytic functions, which utilizes interfacial water evaporation to desalinate seawater and uses the composite nano-carbon film as a catalytic electrode to continuously and fully decompose water to produce high-purity hydrogen and oxygen. Background Art

[0002] As an important clean energy carrier, hydrogen has a high unit energy density of up to 285 MJ / Mol and will play an increasingly important role in the future sustainable energy economy. It is estimated that the global hydrogen energy market demand scale will reach 209 billion US dollars in 2029. However, with the proposal of the carbon peak and carbon neutrality goals, problems such as high energy consumption and environmental pollution caused by the preparation of gray hydrogen through thermal cracking of fossil raw materials have become increasingly prominent. In recent years, with the progress of clean energy power generation technologies such as solar energy, wind energy, and tidal energy, electrolytic water to produce green hydrogen is considered to be one of the most promising hydrogen production technologies.

[0003] However, the global fresh water volume only accounts for 3.5% of the total water resources, and the shortage of fresh water resources severely restricts the development of electrolytic water to produce hydrogen. Therefore, electrolyzing seawater to produce hydrogen is considered to be one of the ideal ways to achieve a green hydrogen economy. Based on this, researchers have proposed two technical solutions: directly electrolyzing seawater to produce hydrogen and electrolyzing after seawater desalination. Direct electrolysis of seawater to produce hydrogen cannot meet the industrial application standards due to problems such as the corrosion of the electrolytic cell by high-concentration chloride ions in seawater, the blockage of the catalytic active sites of the electrode by insoluble substances, and the competition between the chloride ion anodic reaction and the oxygen evolution reaction.

[0004] Thanks to the development of technologies such as reverse osmosis, multi-stage flash distillation, and multi-effect distillation, the electrolysis technology after seawater desalination has greatly reduced the hydrogen production cost. With the proposal of the dual-carbon goal and the progress of renewable energy technologies such as offshore wind power generation, electrolysis after seawater desalination is one of the most ideal solutions. However, there are still some problems to be solved in electrolysis after seawater desalination:

[0005] (1) Methods for desalinating seawater such as reverse osmosis, multi-stage flash distillation, and multi-effect distillation still have a certain energy consumption, increasing the cost of electrolyzing seawater to produce hydrogen;

[0006] (2) The desalinated seawater needs to be collected and then introduced into the electrolytic cell for electrolysis, increasing the process flow and further increasing the hydrogen production cost;

[0007] (3) The cost of electrolytic water catalysts mainly composed of precious metals is high and they need to be bonded to the electrode through naphthol, etc., resulting in a decrease in the activity and stability of the catalyst.

[0008] Therefore, it is of great significance to develop a method that can desalinate seawater using renewable energy and enable the continuous desalination of seawater and electrolysis of water. While reducing the cost of the overall water electrolysis catalyst, improving its activity and stability is expected to achieve low-carbon emissions, low cost, and high-efficiency continuous hydrogen production. Summary of the Invention

[0009] The object of the present invention is to provide a method and device for continuously electrolyzing seawater with a dual-functional composite nanocarbon film of photothermal and electrocatalytic functions. By loading components with electrocatalytic overall water splitting activity on the nanocarbon film to construct a composite nanocarbon film, it can be directly used as the cathode and anode for water electrolysis. Among them, the composite nanocarbon film as the cathode also serves as an interfacial evaporation material to desalinate seawater. After desalination, the seawater undergoes a hydrogen evolution reaction on the cathode film when an electric current is applied, and OH - ions diffuse to the anode film through the electrolyte in the connector and then undergo an oxygen evolution reaction, thereby realizing the overall electrolysis of seawater. By regulating the interfacial water evaporation ability and electrocatalytic overall water splitting performance of the composite nanocarbon film, low-cost, high-efficiency, and continuous electrolysis of seawater can be achieved.

[0010] The technical solution of the present invention is as follows:

[0011] A method for continuously electrolyzing seawater with a dual-functional composite nanocarbon film of photothermal and electrocatalytic functions uses a composite nanocarbon film with high photothermal conversion efficiency to desalinate seawater. This film also serves as an electrode to electrocatalytically decompose water, achieving continuous and efficient electrolysis of seawater. The composite nanocarbon film uses sunlight as an energy source to achieve interfacial water evaporation, and the evaporated fresh water realizes electrolyte exchange in the electrolytic cell through a connector. The composite nanocarbon film loaded with electrocatalytically active substances serves as an electrocatalytic hydrogen evolution cathode, and an electrolytic cell connected by a connector is inserted with a film loaded with a catalytic oxygen evolution function as the anode. After power-on, seawater is continuously and efficiently electrolyzed.

[0012] In the method for continuously electrolyzing seawater with the dual-functional composite nanocarbon film of photothermal and electrocatalytic functions, seawater desalination is achieved by interfacial water evaporation of the composite nanocarbon film. The main body of the film is a porous film constructed by carbon nanotubes, graphene, or nanofibers, which has strong light absorption ability and high photothermal conversion efficiency. It can absorb more than 98% of the light in the spectral range of 400 nm to 2000 nm, and the photothermal conversion efficiency is about 71%. Moreover, the noble metals, high-entropy alloy nanoparticles, or nanowires loaded on the composite nanocarbon film have a plasmonic effect to improve the photothermal conversion efficiency, achieving efficient seawater desalination using sunlight as an energy source.

[0013] The method for continuous full electrolysis of seawater using a photothermal and electrocatalytic bifunctional composite nanocarbon film regulates the photothermal conversion efficiency and water evaporation rate by adjusting the film thickness, pore structure, and hydrophilic-hydrophobic film structure; or, by controlling the size of metal nanoparticles or nanowires supported on the composite nanocarbon film, the photothermal conversion efficiency is enhanced using the plasmonic effect to increase the water evaporation rate.

[0014] The method for continuous full electrolysis of seawater using a photothermal and electrocatalytic bifunctional composite nanocarbon film. The composite nanocarbon film used has the characteristics of high conductivity and high specific surface area. After testing, the sheet resistance of the composite nanocarbon film is only 1 - 2 Ω, and its specific surface area is 300 - 400 m 2 / g. Nanoparticle or nanowire catalysts with different active components are supported by physical deposition or wet chemical synthesis methods; among them, the nanocarbon material film as the cathode supports noble metal platinum nanoparticles or nanowires with high electrocatalytic hydrogen evolution activity; the nanocarbon material film as the anode supports iridium or ruthenium oxide nanoparticles, high-entropy transition metal nanoparticles or nanowires with high electrocatalytic oxygen evolution activity.

[0015] The method for continuous full electrolysis of seawater using a photothermal and electrocatalytic bifunctional composite nanocarbon film. This composite nanocarbon film has a suitable specific surface area to support high-density, high-activity, and high-stability electrocatalytic hydrogen evolution and electrocatalytic oxygen evolution catalysts, achieving efficient and stable electrocatalytic overall water splitting.

[0016] The method for continuous full electrolysis of seawater using a photothermal and electrocatalytic bifunctional composite nanocarbon film. To realize the interfacial thermal evaporation desalination of seawater and electrolysis of water with the composite nanocarbon film, two connected electrolytic cells are required. One electrolytic cell with a larger volume continuously injects seawater and spreads a bifunctional electrocatalytic hydrogen evolution composite nanocarbon film for desalinating seawater and electrolyzing water, with a thickness of 1 - 50 μm; another electrolytic cell adds sulfuric acid or potassium hydroxide electrolyte and inserts an electrocatalytic oxygen evolution composite nanocarbon film as the anode for electrolyzing water, with a thickness of 1 - 50 μm.

[0017] The method for continuous full electrolysis of seawater using a photothermal and electrocatalytic bifunctional composite nanocarbon film. The composite nanocarbon film in the thermal evaporation - hydrogen evolution electrolytic cell is spread on an adiabatic substrate to improve the thermal evaporation efficiency, and a water transport channel is formed by immersing water-absorbing bacterial cellulose between the composite nanocarbon film and the adiabatic substrate in seawater.

[0018] The method for continuous full electrolysis of seawater using a photothermal and electrocatalytic bifunctional composite nanocarbon film. To realize the functions of continuous interfacial thermal evaporation of seawater and electrolysis of water, light irradiation is used to achieve efficient evaporation of seawater, and electrolysis is carried out by applying electricity. When the desalination rate of seawater matches the electrolysis rate, efficient electrolysis of seawater is achieved, and high-purity hydrogen and oxygen are collected in the cathode and anode electrolytic cells respectively.

[0019] A device for continuously electrolyzing seawater with a dual-functional composite nanocarbon film of photothermal and electrocatalytic functions, comprising an anodic oxygen evolution film, evaporated fresh water, a connecting mass transfer pipeline, seawater, a seawater injection port, a photothermal / hydrogen evolution composite nanocarbon film, a water delivery channel, and an adiabatic support mold. The specific structure is as follows:

[0020] The anodic oxygen evolution film and the photothermal / hydrogen evolution composite nanocarbon film are respectively connected to a power source through circuits. The anodic oxygen evolution film is loaded with a nanocarbon composite film with electrocatalytic oxygen evolution activity. The connecting mass transfer pipeline is an intermediate pipeline connecting the evaporation fresh water electrolytic cell where the anodic oxygen evolution film is located and the seawater electrolytic cell where the photothermal / hydrogen evolution composite nanocarbon film is located. The photothermal / hydrogen evolution composite nanocarbon film is a composite film integrating the functions of a photothermal interface thermal evaporation function and an electrocatalytic hydrogen evolution function. The photothermal / hydrogen evolution composite nanocarbon film generates evaporated fresh water through interface thermal evaporation and is transported to the electrolytic cell of the evaporated fresh water through the connecting mass transfer pipeline;

[0021] The seawater electrolytic cell is filled with seawater to be evaporated and purified. A seawater injection port is provided on the side of the seawater electrolytic cell for injecting seawater to ensure the continuity of the interface thermal evaporation and the overall water splitting reaction. The photothermal / hydrogen evolution composite nanocarbon film, the water delivery channel, and the adiabatic support mold are arranged from top to bottom in the upper part of the seawater electrolytic cell. The water delivery channel sucks and transports the lower-layer seawater to the photothermal / hydrogen evolution composite nanocarbon film to achieve interface thermal evaporation; the adiabatic support mold supports the photothermal / hydrogen evolution composite nanocarbon film, separates the photothermal / hydrogen evolution composite nanocarbon film from the seawater liquid level to reduce heat loss, and at the same time facilitates the accumulation of fresh water on the photothermal / hydrogen evolution composite nanocarbon film for electrocatalysis.

[0022] The design concept of the present invention is:

[0023] The present invention utilizes the excellent photothermal conversion performance, high specific surface area, adjustable hydrophilicity and hydrophobicity, rich pore structure and other characteristics of nanocarbon material films such as carbon nanotubes / graphene. High-density, high-activity, small-size low-dimensional nanoparticles are directly supported on the film by physical deposition / wet chemical synthesis and other methods, so that the film has both the functions of desalinating seawater and electrolyzing water; by designing an electrolytic cell, the anode and cathode are connected through a communicating vessel. After illumination and power-on, the cathode composite nanocarbon film realizes seawater desalination and then electrolysis through interface water evaporation. The fresh water diffuses and transports through the communicating vessel to the anode containing the electrolyte solution, and the anode undergoes an oxygen evolution reaction to achieve overall water splitting; the photothermal conversion performance and the electrocatalytic overall water splitting performance of the composite nanocarbon film are adjusted to completely electrolyze the desalinated seawater and achieve low-cost, high-efficiency continuous overall electrolysis of seawater.

[0024] The advantages and beneficial effects of the present invention are:

[0025] (1) The present invention utilizes the excellent photothermal conversion performance, rich pore structure, high specific surface area, and adjustable hydrophilic and hydrophobic characteristics of the macroscopic body of the low-dimensional nanocarbon material film, and enables it to have the dual functions of thermal evaporation desalination of seawater and electrolysis of water by loading low-dimensional nanoparticles / wires.

[0026] (2) The present invention designs an electrolytic cell separated by two electrolytic chambers, enabling the seawater evaporated and collected in the cathode chamber to be connected to the electrolyte solution in the anode chamber through a communicating vessel, and realizing continuous seawater evaporation and electrolysis of water after illumination and power-on.

[0027] (3) The present invention uses sunlight as the light source for seawater desalination. This method produces hydrogen using seawater with rich reserves while reducing carbon emissions, and is expected to promote the large-scale production of hydrogen energy and the resource utilization of seawater. Description of the Drawings

[0028] Figure 1 . Schematic diagram of the device for continuous full electrolysis of seawater by the photothermal and electrocatalytic dual-functional composite nanocarbon film. In the figure, 1 is the anode oxygen evolution film, 2 is the evaporated fresh water, 3 is the communicating mass transfer pipeline, 4 is the seawater, 5 is the seawater injection port, 6 is the photothermal / hydrogen evolution composite nanocarbon film, 7 is the water transport channel, 8 is the adiabatic support mold, and 9 is the power supply.

[0029] Figure 2 . Microstructure of the Pt nanoparticle / single-walled carbon nanotube composite film.

[0030] Figure 3 . Hydrogen evolution performance of the Pt nanoparticle / single-walled carbon nanotube composite film.

[0031] Figure 4 . Microstructure of the IrO2 nanoparticle / single-walled carbon nanotube composite film.

[0032] Figure 5 . Oxygen evolution performance of the IrO2 nanoparticle / single-walled carbon nanotube composite film.

[0033] Figure 6 . Interfacial thermal evaporation performance of the photothermal / electrocatalytic hydrogen evolution dual-functional single-walled carbon nanotube.

[0034] Figure 7 . Stability test of the photothermal and electrocatalytic dual-functional composite nanocarbon film for continuous full electrolysis of seawater. Detailed Embodiments

[0035] In the specific implementation process, the present invention utilizes a composite nanocarbon film with high photothermal conversion efficiency and high electrocatalytic activity for water electrolysis to absorb sunlight to generate heat for evaporating seawater to produce fresh water. At the same time, with this film as the cathode for water electrolysis, an electrolytic cell with a communicating vessel is designed to introduce an electrolyte solution. After illumination and power-on, continuous seawater desalination - overall electrolysis is achieved. That is, a physical deposition / wet chemical synthesis method is used to load electrocatalytically active nanoparticles / nanowires on a porous nanocarbon material (such as graphene, carbon nanotubes, and nanofibers with a porosity of up to 99.9% and pore diameters ranging from a few nanometers to a few micrometers) to construct a composite film. An absorbent material such as bacterial cellulose is laid flat under the film and placed on a heat-insulating carrier, and the other end of the bacterial cellulose is immersed in seawater to form a water channel connecting the seawater and the composite film. The composite film is irradiated with a light source such as sunlight, and the evaporated fresh water is collected to immerse the composite film, which is connected to an electrolytic cell containing an electrolyte solution on one side through a communicating vessel, and power is applied to achieve continuous overall electrolysis of seawater.

[0036] As Figure 1 shown, the device for continuous overall electrolysis of seawater with a photothermal and electrocatalytic bifunctional composite film of the present invention mainly includes an anodic oxygen evolution film 1, evaporated fresh water 2, a communicating mass transfer pipeline 3, seawater 4, a seawater injection port 5, a photothermal / hydrogen evolution composite nanocarbon film 6, a water delivery channel 7, and an adiabatic support mold 8. The specific structure is as follows:

[0037] The anodic oxygen evolution film 1 and the photothermal / hydrogen evolution composite nanocarbon film 6 are respectively connected to a power source 9 through wires. The anodic oxygen evolution film 1 is loaded with a composite film of nanocarbon (such as single-walled carbon nanotubes) with electrocatalytic oxygen evolution activity. The communicating mass transfer pipeline 3 is an intermediate pipeline connecting the evaporation fresh water electrolytic cell where the anodic oxygen evolution film 1 is located and the seawater electrolytic cell where the photothermal / hydrogen evolution composite nanocarbon film 6 is located, and is mainly used for the mass transfer of the electrolyte during the electrocatalytic overall water electrolysis process. The photothermal / hydrogen evolution composite nanocarbon film 6 is a composite film integrating the functions of a photothermal interface thermal evaporation and electrocatalytic hydrogen evolution. The photothermal / hydrogen evolution composite nanocarbon film 6 generates evaporated fresh water 2 through interface thermal evaporation, which is transported to the electrolytic cell of the evaporated fresh water 2 through the communicating mass transfer pipeline 3.

[0038] Seawater 4 to be evaporated and purified is contained in the seawater electrolysis cell. A seawater injection port 5 is provided on the side of the seawater electrolysis cell for injecting seawater to ensure the continuity of interfacial thermal evaporation and overall water splitting reaction. The photothermal / hydrogen evolution composite nanocarbon film 6, water transport channel 7, and adiabatic support mold 8 are arranged from top to bottom in the upper part of the seawater electrolysis cell. The water transport channel 7 is composed of wood pulp fiber, bacterial cellulose, etc., and materials with better water absorption are usually selected, mainly used to absorb and transport the lower-layer seawater to the photothermal / hydrogen evolution composite nanocarbon film 6 for interfacial thermal evaporation. The adiabatic support mold 8 is made of polytetrafluoroethylene, and its main function is to support the photothermal / hydrogen evolution composite nanocarbon film, separate the photothermal / hydrogen evolution composite nanocarbon film 6 from the seawater liquid level to reduce heat loss, and at the same time facilitate the accumulation of fresh water on the photothermal / hydrogen evolution composite nanocarbon film for electrocatalysis.

[0039] Next, the present invention will be further described in detail through examples and drawings.

[0040] Example 1

[0041] In this example, a nanoparticle / single-walled carbon nanotube composite nanocarbon film is used as the electrode and the film for interfacial water evaporation. The specific experimental steps are as follows:

[0042] (1) Preparation of the photothermal / electrocatalytic hydrogen evolution bifunctional composite nanocarbon film and testing of its hydrogen evolution performance;

[0043] High-quality single-walled carbon nanotube films with a thickness of 5 μm are directly prepared and collected by the floating catalyst chemical vapor deposition method. A high-purity platinum target is sputtered by magnetron, with the sputtering power controlled at 50 W and the deposition time at 500 s. After deposition on both sides, a Pt nanoparticle / single-walled carbon nanotube composite film is obtained. As Figure 2 shown, the microscopic structure of the composite film is obtained, and it can be seen that high-density small-sized Pt nanoparticles are supported on the carbon nanotube bundles. The electrocatalytic hydrogen evolution performance of the composite film is tested. In a three-electrode electrochemical workstation (working electrode: rotating disk electrode; counter electrode: graphite electrode; reference electrode: Ag / AgCl electrode; electrolyte solution: 0.5 mol / L H2SO4 solution), linear scanning is carried out at a scanning rate of 0.005 V / s. As Figure 3 shown, after testing, the electrocatalytic hydrogen evolution onset potential of the composite film is 20 mV, and the overpotential at a current density of 10 mA·cm -2 is 71 mV.

[0044] (2) Preparation of the electrocatalytic oxygen evolution composite film and testing of its oxygen evolution performance;

[0045] The preparation method of the single-walled carbon nanotube film is the same as that of Step 1. Take 5 mg of ammonium hexachloroiridate ((NH4)3IrCl6·1.5H2O) and dissolve it in 40 mL of deionized water. Then heat the suspension to 70 °C until ammonium hexachloroiridate is completely dissolved, and seal it in a hydrothermal autoclave. Keep it at 100 °C for 3 h. After the reaction, take out the film and wash it with deionized water to obtain the IrO2 nanoparticle / single-walled carbon nanotube composite film. As Figure 4 shown, the microstructure of the composite film is obtained. The size of the prepared IrO2 nanoparticles is less than 2 nm and they are in a monodispersed state. Test the electrocatalytic oxygen evolution performance of the composite film. In a three-electrode electrochemical workstation (working electrode: rotating disk electrode; counter electrode: platinum wire electrode; reference electrode: Ag / AgCl electrode; electrolyte solution: 1 mol / L KOH aqueous solution), perform linear scanning at a scanning rate of 0.005 V / s. As Figure 5 shown, through electrochemical testing, the electrocatalytic oxygen evolution onset potential of the composite film is 1.462 V, and the potential at a current density of 10 mA·cm -2 is 1.664 V.

[0046] (3) Evaporate seawater by photothermal effect;

[0047] Attach the photothermal / electrocatalytic hydrogen evolution bifunctional composite nanocarbon film prepared in Step 1 to the Figure 1 shown polytetrafluoroethylene adiabatic support mold 8. Lay a layer of wood pulp fiber below the composite nanocarbon film as the water transport channel. Use a solar simulator as the light source to simulate one sun's light intensity and irradiate the composite nanocarbon film above the device to evaporate and desalinate seawater at the interface. Irradiate and measure the change in the mass of seawater. After weighing, calculate the desalination rate of seawater to be 1.2 kg·m -2 ·h -1 .

[0048] (4) Electrochemically catalyze overall water splitting;

[0049] After 6 h of photothermal desalination of seawater, a certain amount of pure water has been collected on the anode side of the device. Add a certain amount of electrolyte (KOH) to the pure water to adjust the pH of the solution to 14. There is a certain height of liquid level at the center of the photothermal / hydrogen evolution composite nanocarbon film to make the composite nanocarbon film and the electrolyte solution fully contact. Then apply a voltage to achieve the complete decomposition of fresh water. As Figure 6 shown, test the overall water splitting performance obtained. It can continuously work for 24 h at a current density of 10 mA·cm -2 . In order to realize the functions of continuous interfacial thermal evaporation of seawater and electrolysis of water, use light irradiation to achieve efficient evaporation of seawater, and apply electricity for electrolysis. Matching the desalination rate with the electrolysis rate can achieve efficient electrolysis of seawater. High-purity hydrogen (volume purity 99.999%) and oxygen (volume purity 99.99%) are collected in the cathode and anode electrolytic cells respectively.

[0050] As Figure 7 shown by the stability test results of continuous full electrolysis of seawater by the dual-functional composite nanocarbon film with photothermal and electrocatalytic functions, it can be seen that the composite film can stably produce hydrogen for 24 h at a current density of 10 mA·cm -2 , and the current density only decays by 10%, indicating its good electrocatalytic hydrogen evolution stability.

[0051] Example 2

[0052] In this example, the nanoparticle / graphene film is used as the electrode and the film for interfacial water evaporation. The specific experimental steps are as follows:

[0053] (1) Preparation of the dual-functional composite nanocarbon film with photothermal / electrocatalytic hydrogen evolution functions;

[0054] First, a graphene film with a thickness of about 10 μm is prepared by chemical vapor deposition, and the hydrophilicity of the graphene film is improved by plasma treatment. Subsequently, Pt nanoparticles are deposited on the graphene film as in step (1) of Example 1.

[0055] (2) Preparation of the electrocatalytic oxygen evolution composite nanocarbon film;

[0056] The preparation method and treatment method of the graphene film are the same as those in step (1) of Example 2. Subsequently, IrO2 nanoparticles are deposited on the graphene film as in step (2) of Example 1.

[0057] (3) Evaporation of seawater by photothermal action;

[0058] Same as step (3) of Example 1.

[0059] (4) Electrocatalytic overall water splitting;

[0060] Same as step (4) of Example 1.

[0061] In this example, the interfacial thermal evaporation performance indexes of the dual-functional composite nanocarbon film with photothermal / electrocatalytic hydrogen evolution functions are as follows: under simulated sunlight illumination of 1 sun, the interfacial seawater evaporation rate is 0.95 kg·m -2 ·h -1 . The stability test performance indexes of the dual-functional composite nanocarbon film for continuous full electrolysis of seawater are as follows: it can stably perform overall water splitting for 24 h at a current density of 10 mA·cm -2 , and the current density only decays by 14%.

[0062] Example 3

[0063] In this example, the nanoparticle / nanocarbon fiber film is used as the electrode and the film for interfacial water evaporation. The specific experimental steps are as follows:

[0064] (1) Preparation of a dual-functional composite nanocarbon film for photo-thermal / electro-catalytic hydrogen evolution;

[0065] Purchase a commercial nanocarbon fiber film with a thickness of 30 μm, and then deposit Pt nanoparticles on the film in the same manner as in step (1) of Example 1.

[0066] (2) Preparation of an electro-catalytic oxygen evolution composite nanocarbon film;

[0067] Obtain and process the nanocarbon fiber film in the same manner as in step (1) of Example 3, and then deposit IrO2 nanoparticles on the carbon fiber film in the same manner as in step (2) of Example 1.

[0068] (3) Evaporation of seawater by photo-thermal action;

[0069] Same as step (3) of Example 1.

[0070] (4) Electro-catalytic overall water splitting;

[0071] Same as step (4) of Example 1.

[0072] In this example, the interface thermal evaporation performance indexes of the dual-functional composite nanocarbon film for photo-thermal / electro-catalytic hydrogen evolution are as follows: under the illumination of 1 simulated sunlight, the interface seawater evaporation rate is 0.83 kg·m -2 ·h -1 . The stability test performance indexes of the dual-functional composite nanocarbon film for continuous overall electrolysis of seawater are as follows: it can stably perform overall water splitting for 24 h at a current density of 10 mA·cm -2 , and the current density only decays by 17%.

[0073] Example 4

[0074] In this example, a composite nanocarbon film of metal nanowires / single-walled carbon nanotubes is used as the electrode and the film for interface water evaporation. The specific experimental steps are as follows:

[0075] (1) Preparation of a dual-functional composite nanocarbon film for photo-thermal / electro-catalytic hydrogen evolution;

[0076] Take a certain amount of platinum acetylacetonate, iron acetylacetonate, nickel acetylacetonate (10 mg each), 30 mg of didodecyldimethylammonium bromide, and 40 mg of anhydrous glucose, place them in a 10 ml oleylamine solvent for ultrasonic dispersion to form a solution, put a single-walled carbon nanotube film with a thickness of 50 μm into the solution, and heat it in an oil bath at 170 °C for 30 min. After the reaction, take out the film and wash it with absolute ethanol to remove the surfactant to obtain an ultrafine PtFeNi nanowire / single-walled carbon nanotube composite nanocarbon film. The radial size of the ultrafine PtFeNi nanowires is 1 - 2 nm.

[0077] (2) Preparation of an electro-catalytic oxygen evolution composite nanocarbon film;

[0078] Same as step (1) of Example 4.

[0079] (3) Evaporate seawater by photothermal effect;

[0080] Same as step (3) of Example 1.

[0081] (4) Electro-catalytic overall water splitting;

[0082] Same as step (4) of Example 1.

[0083] In this example, the interfacial thermal evaporation performance indicators of the photothermal / electro-catalytic hydrogen evolution bifunctional composite nanocarbon film are as follows: under the simulation of 1 sun illumination, the interfacial seawater evaporation rate is 1.13 kg·m -2 ·h -1 . The stability test performance indicators of the photothermal / electro-catalytic bifunctional composite nanocarbon film for continuous overall electrolysis of seawater are as follows: it can stably split water overall for 24 h at a current density of 10 mA·cm -2 , and the current density only decays by 12%.

[0084] The implementation results show that the composite nanocarbon film of the present invention can achieve continuous desalination and electrolysis of seawater, efficiently obtain clean energy hydrogen under low carbon emissions, and is expected to promote the low-cost large-scale application of hydrogen energy.

[0085] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made based on the present invention, which are obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection required by the present invention.

Claims

1. A method for continuous total electrolysis of seawater by a dual-functional composite nanocarbon film with photothermal and electrocatalytic functions, characterized in that, Desalinate seawater using a composite nanocarbon film with high photothermal conversion efficiency. The composite nanocarbon film also serves as an electrode for electrocatalytic water splitting to achieve continuous and efficient electrolysis of seawater. The composite nanocarbon film uses sunlight as an energy source to achieve interfacial water evaporation, and after evaporation, the fresh water realizes electrolyte exchange in the electrolytic cell through a connected mass transfer pipeline. To realize the desalination of seawater by interfacial thermal evaporation of the composite nanocarbon film and electrolysis of water, two electrolytic cells need to be connected by a connected mass transfer pipeline. In one electrolytic cell with a larger volume, seawater is continuously injected and a bifunctional electrocatalytic hydrogen evolution composite nanocarbon film for desalinating seawater and electrolyzing water is laid flat, with a thickness of 1 - 50 μm. In the other electrolytic cell, sulfuric acid or potassium hydroxide electrolyte is added and an electrocatalytic oxygen evolution composite nanocarbon film serving as the anode for electrolyzing water is inserted, with a thickness of 1 - 50 μm. Among them, the electrocatalytic hydrogen evolution composite nanocarbon film serves as the cathode, and the electrocatalytic oxygen evolution composite nanocarbon film is a composite nanocarbon film supporting an electrocatalytic oxygen evolution catalyst. Use the interfacial water evaporation of the composite nanocarbon film to desalinate seawater. The main body of the composite nanocarbon film is a porous film constructed by carbon nanotubes, graphene, or nanofibers, which has strong light absorption ability and high photothermal conversion efficiency. Moreover, the noble metals, high-entropy alloy nanoparticles, or nanowires supported by the electrocatalytic hydrogen evolution composite nanocarbon film not only have the function of hydrogen evolution but also have a plasmonic effect to improve the photothermal conversion efficiency, and use sunlight as an energy source to achieve efficient seawater desalination.

2. The method for continuously and fully electrolyzing seawater by the photothermal and electrocatalytic dual-functional composite nanocarbon film according to claim 1, characterized in that, Regulate the photothermal conversion efficiency and water evaporation rate by adjusting the thickness, pore structure, and hydrophilic-hydrophobic film structure of the composite nanocarbon film. Or, by regulating the size of the high-entropy alloy nanoparticles or nanowires supported by the composite nanocarbon film, use the plasmonic effect to enhance the photothermal conversion efficiency and increase the water evaporation rate.

3. The method for continuous total electrolysis of seawater by the photothermal and electrocatalytic bifunctional composite nanocarbon film according to claim 1, wherein The composite carbon nanotube film used has the characteristics of high conductivity and high specific surface area. After testing, the sheet resistance of the composite carbon nanotube film is only 1-2 Ω, and its specific surface area is 300-400 m 2 / g. Nanoparticles or nanowire catalysts with different active components are supported by physical deposition or wet chemical synthesis methods. Among them, the electrocatalytic hydrogen evolution composite carbon nanotube film as the cathode supports noble metal platinum nanoparticles or nanowires with high electrocatalytic hydrogen evolution activity; the electrocatalytic oxygen evolution composite carbon nanotube film as the anode supports iridium or ruthenium oxide nanoparticles, high-entropy transition metal nanoparticles or nanowires with high electrocatalytic oxygen evolution activity.

4. The method for continuous total electrolysis of seawater by the photothermal and electrocatalytic bifunctional composite nanocarbon film according to claim 1, wherein, The composite nanocarbon film in the thermal evaporation - hydrogen evolution electrolytic cell is laid flat on an adiabatic substrate to improve the thermal evaporation efficiency, and a bacterial cellulose with water absorption ability is immersed in seawater between the composite nanocarbon film and the adiabatic substrate as a water transport channel.

5. The method for continuous full electrolysis of seawater by the photothermal and electrocatalytic bifunctional composite nanocarbon film according to claim 1, characterized in that, To realize the functions of continuous interfacial thermal evaporation of seawater and electrolysis of water, use light irradiation to achieve efficient evaporation of seawater, conduct electrolysis by electricity, and match the desalination rate and electrolysis rate of seawater to achieve efficient electrolysis of seawater, and collect high-purity hydrogen and oxygen in the cathode and anode electrolytic cells respectively.

6. An apparatus for continuously and fully electrolyzing seawater using a photothermal and electrocatalytic bifunctional composite nanocarbon film used in the method according to any one of claims 1 to 5, characterized in that, It includes an electrocatalytic oxygen evolution composite nanocarbon film, evaporated fresh water, a connected mass transfer pipeline, seawater, a seawater injection port, an electrocatalytic hydrogen evolution composite nanocarbon film, a water transport channel, and an adiabatic support mold. The specific structure is as follows: The electrocatalytic oxygen evolution composite nanocarbon film and the electrocatalytic hydrogen evolution composite nanocarbon film are respectively connected to the power supply through wires. The connected mass transfer pipeline is an intermediate pipeline connecting the evaporation fresh water electrolytic cell where the electrocatalytic oxygen evolution composite nanocarbon film is located and the seawater electrolytic cell where the electrocatalytic hydrogen evolution composite nanocarbon film is located. The electrocatalytic hydrogen evolution composite nanocarbon film is a composite film integrating the functions of photothermal interfacial thermal evaporation and electrocatalytic hydrogen evolution. The electrocatalytic hydrogen evolution composite nanocarbon film generates evaporated fresh water through interfacial thermal evaporation and transports it to the electrolytic cell for evaporated fresh water through the connected mass transfer pipeline. Seawater to be evaporated and purified is contained in the seawater electrolysis cell. A seawater injection port is provided on the side of the seawater electrolysis cell for injecting seawater to ensure the continuity of interfacial thermal evaporation and overall water splitting reaction. The electrocatalytic hydrogen evolution composite nanocarbon film, water delivery channel, and adiabatic support mold are arranged from top to bottom in the upper part of the seawater electrolysis cell. The water delivery channel sucks and transports the seawater in the lower layer to the electrocatalytic hydrogen evolution composite nanocarbon film to achieve interfacial thermal evaporation. The adiabatic support mold supports the electrocatalytic hydrogen evolution composite nanocarbon film, separates the electrocatalytic hydrogen evolution composite nanocarbon film from the seawater liquid level to reduce heat loss, and at the same time facilitates the accumulation of fresh water on the electrocatalytic hydrogen evolution composite nanocarbon film for electrocatalysis.

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