Preparation method of bifunctional nano flower-shaped photoelectrocatalytic material and application of bifunctional nano flower-shaped photoelectrocatalytic material in collaborative production of ammonia and iodine

Abstract

The invention belongs to the technical field of photoelectrocatalysis ammonia synthesis catalysts, and particularly relates to a preparation method of a bifunctional nano flower-shaped photoelectrocatalysis material and application of the bifunctional nano flower-shaped photoelectrocatalysis material in collaborative production of ammonia and iodine. The preparation method comprises the following steps: performing in-situ growth of CoWO4 nanoflowers on a Ti net substrate through a hydrothermal method, and obtaining the CoP / CoWO4 / Ti integrated electrode through an in-situ phosphorization strategy. A CoP / CoWO4 / Ti integrated electrode is adopted as a bifunctional photoelectric cathode, and NH3 production through cathode nitrate reduction and anode iodine oxidation synergetic iodine generation can be achieved. Under the driving of a specific potential, the yield of NH3 synthesized by a NO3RR | I OR battery system is about 2.1 mg cm <-2 > h <-1 >, and the yield of I2 is about 0.8 mmol. The photoelectrochemical cell constructed on the basis of the bifunctional nano flower-shaped photoelectrocatalysis material has the characteristics of high Faraday efficiency, high ammonia yield, high conversion rate, excellent repeatability and the like, and has the advantages of low cost, simple process, environmental protection, no pollution and energy conservation.

Description

Technical Field

[0001] This invention belongs to the field of photoelectrocatalytic ammonia synthesis catalyst technology, specifically relating to a method for preparing a bifunctional nanoflower-like photoelectrocatalytic material and its application in the synergistic production of ammonia and iodine. Background Technology

[0002] Ammonia, as an important energy carrier and chemical raw material, holds strategic value in hydrogen storage and renewable energy conversion. Currently, the industrial synthesis of ammonia mainly relies on the Haber-Bosch process, but this process has been found to have problems such as high operating costs and serious environmental pollution. Although the nitrogen reduction-based synthesis route has theoretical advantages in terms of environmental protection, the low solubility and high dissociation energy of nitrogen molecules result in low NH3 yields, severely hindering the industrial production of ammonia. Therefore, it is necessary to develop an efficient, economical, and cost-effective ammonia synthesis process.

[0003] Photoelectrocatalytic nitrate reduction technology uses water as a proton source to achieve the directional conversion of nitrate to ammonia under ambient temperature and pressure, providing an innovative solution for ammonia synthesis under carbon neutrality. Compared with traditional ammonia production methods, the advantages of photoelectrocatalytic ammonia production are mainly reflected in the following aspects: (1) Using solar energy as the driving force, it realizes the direct conversion of clean energy to chemical energy, which meets the sustainable development needs of renewable energy utilization; (2) The reaction process can be carried out under ambient temperature and pressure, breaking through the dependence of traditional processes on high temperature and high pressure environments, significantly reducing system energy consumption and carbon emissions; (3) Semiconductor catalysts, through the directional migration mechanism of photogenerated carriers, synergistically utilize light energy and electrical energy to achieve efficient energy transfer and conversion, providing a new way for precise control of reaction pathways. In addition, nitrate, as a common environmental pollutant, is widely present in water bodies and soil in the natural environment. Excessive accumulation of nitrate in the natural environment leads to eutrophication of water bodies, which in turn destroys the nitrogen cycle in nature. Therefore, exploring photoelectrocatalytic nitrate reduction to NH3 under neutral conditions has a wider range of application value.

[0004] Photoelectrochemical cells constructed using anode-cathode coupling can reduce energy loss by converting solar energy through a photocathode and anode. Compared to the anodic oxidation reaction of water splitting (OER, 1.23 V vs standard hydrogen electrode potential (RHE)), the iodine oxidation reaction (IOR) requires a lower theoretical potential (0.57 V vs RHE), showing greater potential to replace OER for efficient NH3 production. Iodine produced by iodine oxidation is a fundamental chemical raw material with significant applications in pharmaceuticals, food additives, and fine chemicals. By constructing a bifunctional electrochemical system coupling cathode nitrate reduction and anodic iodine oxidation, the overpotential of the electrolytic cell can be effectively reduced, simultaneously driving the synthesis of two high-value chemicals: NH3 and I2. This synergistic catalytic mechanism effectively alleviates the high energy consumption problem of traditional water oxidation processes while increasing the value of anode and cathode products, providing a new approach to improving energy conversion efficiency and product selectivity. Summary of the Invention

[0005] One objective of this invention is to provide a bifunctional nanoflower-like photoelectrocatalytic material CoP / CoWO4 / Ti and its preparation method.

[0006] The second objective of this invention is to provide a method for achieving efficient nitrate reduction to ammonia production using a bifunctional nanoflower-like photoelectrocatalyst material CoP / CoWO4 / Ti.

[0007] The third objective of this invention is to provide a method for achieving efficient electrocatalytic iodine oxidation using a bifunctional nanoflower-like photoelectrocatalytic material CoP / CoWO4 / Ti.

[0008] The fourth objective of this invention is to provide a method for achieving efficient nitrate reduction to ammonia and iodine co-production in a photoelectrochemical cell using a bifunctional nanoflower-like photocatalytic material CoP / CoWO4 / Ti.

[0009] The technical solution adopted in this invention is as follows:

[0010] A method for preparing a bifunctional nanoflower-like photoelectrocatalytic material includes the following steps:

[0011] 1) Dissolve trisodium citrate in deionized water, add CoCl2 under vigorous stirring to obtain solution A; dissolve Na2WO4 in deionized water to obtain solution B; slowly add solution B to solution A under continuous stirring, and continue stirring for 2 hours to form a uniform pink transparent solution.

[0012] 2) The pink transparent solution and the pretreated Ti mesh were transferred to an autoclave for hydrothermal reaction. After the reaction was completed, the mixture was allowed to cool naturally to room temperature. The precipitate was collected by centrifugation and washed repeatedly with deionized water. The mixture was then dried overnight in an oven at 60°C to obtain CoWO4 / Ti.

[0013] 3) Place CoWO4 / Ti and NaH2PO2 into two ceramic boats respectively. Place NaH2PO2 in the upstream zone of the tube furnace and CoWO4 / Ti in the downstream zone, maintaining a distance of 3 cm between them. In a N2 atmosphere, incubate at a rate of 5℃ / min. -1 CoP / CoWO4 / Ti can be obtained by calcining at 350℃ for 2 hours.

[0014] Furthermore, in the above preparation method, in step 1), the molar ratio of trisodium citrate, CoCl2, and Na2WO4 is 2:1:1.

[0015] Furthermore, in the above preparation method, step 2), the hydrothermal reaction is carried out at 200°C for 12 h.

[0016] Furthermore, in the above preparation method, in step 3), the mass ratio of CoWO4 / Ti and NaH2PO2 is 1:1.

[0017] Application of bifunctional nanoflower-like photocatalytic materials prepared by any of the above methods in the photocatalytic reduction of nitrate to NH3.

[0018] Furthermore, the application method of the bifunctional nanoflower-like photoelectrocatalytic material in the photoelectrocatalytic reduction of nitrate to NH3 is as follows: In a standard three-electrode system, a CHI 660E electrochemical workstation was used, with the bifunctional nanoflower-like photoelectrocatalytic material CoP / CoWO4 / Ti as the working electrode, an Ag / AgCl electrode as the reference electrode, a Pt sheet as the counter electrode, a 300 W xenon lamp with λ>420nm as the visible light source, and an argon-saturated neutral mixed electrolyte of 0.5 M Na2SO4 and 0.05 M NaNO3. The voltage was -1.0 V vs RHE, and the photoelectrocatalytic reduction of nitrate was carried out.

[0019] Application of bifunctional nanoflower-like photoelectrocatalytic materials prepared by any of the above methods in electrocatalytic iodine oxidation.

[0020] Furthermore, the application method of the bifunctional nanoflower-like photoelectrocatalyst in the electrocatalytic oxidation of iodine is as follows: A CHI 660E electrochemical workstation was used in a standard three-electrode system. The bifunctional nanoflower-like photoelectrocatalyst CoP / CoWO4 / Ti was used as the working electrode, the Ag / AgCl electrode as the reference electrode, and the Pt sheet as the counter electrode. The electrolyte solution was a mixture of 0.5 M H₂SO₄ and 0.5 M KI acid-washed electrolyte, and a constant stirring frequency of 500 rpm and a current of 15 mA cm⁻¹ were maintained. -2 It undergoes an electrocatalytic iodine oxidation reaction.

[0021] Application of bifunctional nanoflower-like photocatalytic materials prepared by any of the above methods in the photocatalytic co-production of ammonia and iodine.

[0022] Furthermore, the application method of bifunctional nanoflower-like photoelectrocatalytic materials in the photoelectrocatalytic co-production of ammonia and iodine is as follows: A CHI 660E electrochemical workstation is used in an H-type electrolytic cell. The bifunctional nanoflower-like photoelectrocatalytic materials CoP / CoWO4 / Ti are used as the cathode and anode, respectively, with Ag / AgCl as the reference electrode. A 300 W xenon lamp with λ>420 nm is used as the visible light source to irradiate the cathode. The cathode chamber and anode chamber are separated by a Nafion membrane. The anode electrolyte solution is a 0.5 M H2SO4 and 0.5 M KI acidic mixed solution, and the cathode electrolyte solution is a 0.5 M Na2SO4 and 0.05 M NaNO3 neutral mixed solution. The voltage is -1.2 Vvs RHE, and the photoelectrocatalytic co-production of NH3 and I2 is carried out.

[0023] The beneficial effects of this invention are:

[0024] 1. This invention presents a novel bifunctional nanoflower-like photoelectrocatalyst material, CoP / CoWO4 / Ti, prepared using a hydrothermal method combined with low-temperature in-situ phosphating. The preparation process is simple. This invention utilizes the unique Schottky junction characteristics to construct a heterojunction catalyst with close metal-semiconductor interface contact, which promotes electron transfer and increases the reaction rate. The presence of the Schottky barrier inhibits electron-hole recombination, enhancing the catalyst's redox capability. The advantages of using bifunctional CoP / CoWO4 / Ti lie in its highly efficient synergistic catalysis. Through the coupling of cathode nitrate reduction and anolyte iodine oxidation, simultaneous pollutant degradation and resource recovery are achieved, while reducing energy consumption, simplifying system design, and improving overall reaction efficiency.

[0025] 2. This invention features simplicity, high efficiency, low cost, and low energy consumption. Utilizing the cascaded catalyst of this invention, the selective control of the competing reactions of nitrate enrichment and hydrogen evolution is achieved through the synergistic effect of different reaction sites. This not only facilitates the adsorption of active substances but also provides a large amount of H*, improving the selectivity of nitrate reduction and enabling the efficient production of chemical value-added products. Under a specific additional bias voltage, the yield of NH3 synthesized by the CoP / CoWO4 / Ti integrated electrode in the NO3RR‖IOR battery system is approximately 2.1 mg / cm³. -2 h -1 The I2 yield is approximately 0.8 mmol, and it also exhibits good recyclability, providing important theoretical and experimental basis for the development of efficient and stable photoelectrochemical synthesis systems. Attached Figure Description

[0026] Figure 1X-ray diffraction (XRD) patterns of CoP, CoWO4, and CoP / CoWO4.

[0027] Figure 2 Scanning electron microscope (SEM) images of CoWO4 (a) and CoP / CoWO4 (b).

[0028] Figure 3 (a) is the X-ray photoelectron spectrum (XPS) of CoP / CoWO4, (b) is the O 1s fine spectrum of CoWO4 and CoP / CoWO4, and (c) is the P 2p fine spectrum of CoP and CoP / CoWO4.

[0029] Figure 4 (a) shows the UV-Vis diffuse reflectance absorption spectra of CoWO4 and CoP (inset: Eg calculated spectrum of CoWO4), and (b) shows the Mott-Schottky curve of CoWO4.

[0030] Figure 5 The LSV curves are for different electrodes under different conditions.

[0031] Figure 6 (a) is a graph showing the yield of NH3 synthesized by photoelectrocatalytic nitrate reduction using CoWO4 / Ti, CoP / Ti, and CoP / CoWO4 / Ti; (b) is a graph showing the yield of NH3 synthesized by photoelectrocatalytic nitrate reduction using CoP / CoWO4 / Ti at different potentials; (c) is a graph showing the NO3 synthesis during the photoelectrocatalytic nitrate reduction process using CoP / CoWO4 / Ti. - NO2 - And NH3 change curve.

[0032] Figure 7 The graph shows the performance of CoP / CoWO4 / Ti photoelectrocatalytic nitrate reduction and recycling.

[0033] Figure 8 (a) shows the LSV curves of IOR and OER catalyzed by CoP / CoWO4 / Ti, and (b) shows the I2 yield obtained by IOR catalyzed by CoP / CoWO4 / Ti at different current densities.

[0034] Figure 9 (a) shows the LSV curves of the CoP / CoWO4 / Ti integrated electrode in the NO3RR‖IOR and NO3RR‖OER coupled battery systems, and (b) shows the yields of NH3 and I2 catalyzed by the NO3RR‖IOR coupled battery system at different potentials.

[0035] Figure 10 The recycling performance of the NO3RR‖IOR coupled battery system (illustration: image of solution color change during reaction and XRD pattern of I2 obtained at the end). Detailed Implementation

[0036] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The embodiments listed below are merely for further understanding and implementation of the technical solution of the present invention and do not constitute a further limitation on the claims of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0037] Example 1: Preparation of bifunctional CoP / CoWO4 catalyst

[0038] 2.9 g of trisodium citrate (10 mmol) was dissolved in 70 mL of deionized water. 1.2 g of CoCl2 (5 mmol) was added under vigorous stirring to obtain solution A. Separately, 5 mmol of Na2WO4 was dissolved in 30 mL of deionized water to obtain solution B. Solution B was slowly added dropwise to solution A under continuous stirring. After stirring for 2 h, a homogeneous pink transparent solution was formed. This pink transparent solution was transferred to a 100 mL autoclave and hydrothermally reacted at 200 °C for 12 h. After the reaction, the mixture was allowed to cool to room temperature, the precipitate was collected by centrifugation and repeatedly washed with deionized water. The precipitate was then dried overnight in an oven at 60 °C to obtain CoWO4. CoWO4 and NaH2PO2 (mass ratio 1:1) were then placed in two separate ceramic boats. NaH2PO2 was placed in the upstream zone of a tube furnace, and CoWO4 in the downstream zone, with a distance of 3 cm between them. The furnace was then heated at a rate of 5 °C / min under a N2 atmosphere. -1 CoP / CoWO4 can be obtained by calcining at 350℃ for 2 hours.

[0039] Preparation method of CoP catalyst:

[0040] 0.655 g of Co(NO3)2·6H2O and 0.675 g of urea were dissolved in 50 mL of deionized water. The mixed solution was transferred to a polytetrafluoroethylene-lined autoclave and hydrothermally heated at 120 °C for 6 h to obtain the precursor. The obtained precursor was then subjected to the phosphating method described above, and the resulting gray-black powder was CoP.

[0041] Results analysis:

[0042] The catalyst prepared in Example 1 was characterized by X-ray diffraction (XRD). Figure 1It can be observed that the XRD pattern of CoP / CoWO4 simultaneously shows the characteristic diffraction peaks of CoWO4 (PDF#15-0867) and CoP (PDF#29-0497), indicating the successful synthesis of the CoP / CoWO4 catalyst.

[0043] The catalyst prepared in Example 1 was characterized by scanning electron microscopy (SEM). Figure 2 As shown in figure a, CoWO4 is formed by stacking nanosheets to create a nanoflower morphology with a size of approximately 2 μm. CoP / CoWO4 was obtained by in-situ phosphating with PH3 generated from the thermal decomposition of NaH2PO2. Figure 2 b) The morphology of the nanoflowers with CoWO4 is still maintained.

[0044] X-ray photoelectron spectroscopy (XPS) analysis was performed on the CoP / CoWO4 catalyst, such as... Figure 3 As shown. Figure 3 The XPS full spectrum of CoP / CoWO4 (a) contains four elements: Co, W, P, and O. From... Figure 3 As can be observed in bc, the P 2p of the CoP / CoWO4 heterojunction catalyst undergoes a significant negative shift relative to pure CoP, while the O 1s shifts positively relative to pure CoWO4. This indicates that surface electrons flow from CoWO4 to CoP, and this redistribution of surface charge is beneficial to the subsequent nitrate reduction reaction.

[0045] UV-Vis diffuse reflectance spectroscopy was performed on CoWO4 and CoP, and the results are as follows: Figure 4 As shown in Figure a, compared to CoWO4, CoP exhibits excellent photoresponse in the 200-800 nm wavelength range, demonstrating superior broad-spectrum trapping capability. The band gap (Eg) of CoWO4, calculated using the Kubelka-Munk equation, is 2.6 eV. CoP, with its smaller band gap, can act as an electron acceptor in Schottky junctions, accelerating electron transport. The Mott-Schottky ratio measurements of CoWO4 and CoP are shown in Figure a. Figure 4 As shown in b, CoWO4 is an n-type semiconductor, and the flat-band potential (E) of CoWO4 is... FB The value is -0.36 eV (vs. NHE). Typically, the conduction band potential of an n-type semiconductor is close to its flat band potential, exceeding it by 0.1-0.2 eV. Therefore, the estimated conduction band potential (E) of CoWO4 is... CB The value is -0.46 eV (vs. NHE). From the formula E... g =E VB -E CB The valence band potential (E) of CoWO4 was obtained. VB The value is 2.14 eV (vs. NHE).

[0046] Example 2: Fabrication of a bifunctional CoP / CoWO4 / Ti integrated electrode

[0047] 2.9 g of trisodium citrate (10 mmol) was dissolved in 70 mL of deionized water. 1.2 g of CoCl2 (5 mmol) was added under vigorous stirring to obtain solution A. Separately, 5 mmol of Na2WO4 was dissolved in 30 mL of deionized water to obtain solution B. Solution B was slowly added dropwise to solution A under continuous stirring. After stirring for 2 h, a homogeneous pink transparent solution was formed. The above pink transparent solution and the pretreated Ti mesh were transferred to a 100 mL autoclave and hydrothermally reacted at 200 °C for 12 h. After the reaction, the mixture was allowed to cool naturally to room temperature. The precipitate was collected by centrifugation and repeatedly washed with deionized water. It was then dried overnight in an oven at 60 °C to obtain CoWO4 / Ti. CoWO4 / Ti and NaH2PO2 (mass ratio 1:1) were then loaded into two separate ceramic boats. NaH2PO2 was placed in the upstream zone of a tube furnace, and CoWO4 / Ti was placed in the downstream zone, with a distance of 3 cm between them. The mixture was then incubated at a rate of 5 °C / min under a N2 atmosphere. -1 CoP / CoWO4 / Ti can be obtained by calcining at 350℃ for 2 hours.

[0048] Example 3: Performance Study of Photoelectrocatalytic Nitrate Reduction (NO3RR)

[0049] The tests were conducted using a CHI 660E electrochemical workstation in a standard three-electrode system. A CoP / CoWO4 / Ti electrode was used as the working electrode, an Ag / AgCl electrode as the reference electrode, a Pt sheet as the counter electrode, and a 300 W xenon lamp (λ>420nm) as the visible light source. The electrolyte solution was a neutral mixture of 0.5 M Na2SO4 and 0.05 M NaNO3 saturated with argon. The working potentials used in the tests (vs. Ag / AgCl) were all determined according to E... RHE = E Ag / AgCl +0.0592 pH +0.1976 translates to potential relative to the standard hydrogen electrode (vs. RHE). The linear sweep voltammetry (LSV) curve has a scan potential range of 0 to -1.4 V vs. RHE, with a scan rate of 5 mV s. -1 The rotation speed was 200 rpm. The photoelectrochemical NO3-reactive oxygen species (NO3RR) was measured using a chronovoltammetric method at a voltage of -1.0 V vs. RHE. After 1 h of continuous reaction, the NH4+ concentration in the electrolyte was measured using an ammonia-sensitive electrode. + The concentration of NO3 was determined, and the corresponding ammonia yield and Faraday efficiency (FE) were calculated. - and NO2 -The content was quantitatively determined by sulfonamide-assisted and N-(1-naphthalene)ethylenediamine-assisted ultraviolet-visible spectrophotometry, respectively.

[0050] Results analysis:

[0051] Depend on Figure 5 It can be seen that, under visible light irradiation but without NO3... - Under these conditions, CoP / CoWO4 / Ti exhibited the largest current response and a lower onset potential, indicating superior catalytic activity; with visible light irradiation and the presence of NO3... - In this case, CoP / CoWO4 / Ti exhibited a significantly improved current density, indicating that NO3... - It participates in NO3RR as an active reactant in the catalytic process; when there is no visible light irradiation but NO3 is present... - In the presence of visible light, the current density of the CoP / CoWO4 / Ti electrocatalyzed NO3RR was significantly reduced, indicating that the introduction of visible light promoted the NO3RR process.

[0052] Depend on Figure 6 As can be seen from ab, at a voltage of -1.0 V, the ammonia production yield of the CoP / CoWO4 / Ti heterojunction photoelectrocatalysis is 2.5 mgh. -1 cm -2 The FE (exchange factor) was 77.4%, significantly higher than that of the comparative materials CoWO4 / Ti and CoP / Ti. With increasing voltage, the ammonia production of CoP / CoWO4 / Ti also increased, but the FE showed a trend of first increasing and then decreasing, possibly due to competing side reactions at more negative potentials, leading to the decrease in FE. Simultaneously, the concentration changes of nitrogen species (NO3) were monitored throughout the reaction process. - NO2 - (and NH3), the results are as follows Figure 6 As shown in c. With NO3 - The decrease in concentration means that most of the NO3 - It is converted to NH3 within 60 minutes, but a small amount of NO2 remains. - NO2 is generated. - The concentration of NO3 initially increases and then decreases as the reaction proceeds. This result indicates that as the reaction continues, the concentration of NO3... - First it is reduced to NO2 - The generated NO2 - It is further reduced to NH3 on the electrode surface, and finally NO3. - The conversion rate is approximately 79.9%.

[0053] Depend on Figure 7It can be seen that after 10 cycles at a potential of -1.0 V (with the electrolyte solution replaced every 1 h), the yield of ammonia and FE synthesized by the photoelectrochemical catalysis of the CoP / CoWO4 / Ti heterojunction did not decrease significantly, indicating that CoP / CoWO4 / Ti has good recyclability and catalytic stability.

[0054] Example 4: Performance Study of Electrocatalytic Iodine Oxidation (IOR)

[0055] The tests were conducted using a CHI 660E electrochemical workstation in a standard three-electrode system. CoP / CoWO4 / Ti was used as the working electrode, Ag / AgCl as the reference electrode, and a Pt sheet as the counter electrode. The electrolyte solution was a mixture of 0.5 M H2SO4 and 0.5 MKI acid-washed electrolyte, and a constant stirring frequency (500 rpm) was maintained. The working potentials (vs. Ag / AgCl) used in the tests were all in accordance with E... RHE = E Ag / AgCl +0.0592 pH +0.1976 translates to potential relative to the standard hydrogen electrode (vs. RHE). The linear sweep voltammetry (LSV) curve was plotted over a potential range of 0.8–1.8 V vs. RHE at a scan rate of 5 mV s. -1 The rotation speed was 200 rpm. Electrocatalytic IOR was measured using the chronoamperometry method with a current of 15 mA cm⁻¹. -2 After the reaction continued for 1 hour, the generated I2 was quantitatively detected by iodometric titration.

[0056] Results analysis:

[0057] Depend on Figure 8 As can be seen, CoP / CoWO4 / Ti exhibits higher electrocatalytic IOR activity, requiring a lower potential to achieve the same current intensity compared to oxygen evolution reaction (OER). This result indicates that the battery constructed using anodic IOR instead of OER is more energy-efficient. Figure 8 As can be seen from b, the yield of I2 increases with increasing current density, at a current density of 15 mA cm⁻¹. -2 The I2 production at that time was approximately 0.778 mmol.

[0058] Example 5: Bifunctional CoP / CoWO4 / Ti photoelectrocatalytic co-production of ammonia and iodine

[0059] The tests were conducted using a CHI 660E electrochemical workstation in an H-type electrolytic cell. CoP / CoWO4 / Ti was used as the cathode and anode, respectively, with Ag / AgCl as the reference electrode. A 300 W xenon lamp (λ>420nm) was used as the visible light source to irradiate the cathode. The cathode and anode chambers were separated by a Nafion membrane. The anode electrolyte solution was a mixed acidic solution of 0.5M H2SO4 and 0.5M KI, while the cathode electrolyte solution was a neutral mixed solution of 0.5M Na2SO4 and 0.05M NaNO3. The operating potentials (vs. Ag / AgCl) used in the tests were all in accordance with E RHE = E Ag / AgCl +0.0592 pH +0.1976 translates to potential relative to the standard hydrogen electrode (vs. RHE). The linear sweep voltammetry (LSV) curve has a scan potential range of 0 to -1.4 V vs. RHE, with a scan rate of 5 mV s. -1 The rotation speed was 200 rpm. The photoelectrochemical co-production of NH3 and I2 was carried out using a chronovoltammetric method at a voltage of -1.2 V vs RHE. After 1 h of continuous reaction, the NH3 produced at the cathode was quantitatively analyzed using an ammonia-sensitive electrode, and the I2 produced at the anode was quantitatively detected using iodometric titration.

[0060] Results analysis:

[0061] Depend on Figure 9 As can be seen, compared with the NO3RR‖OER battery system, the NO3RR‖IOR battery system exhibits a stronger current response, with a current density of 10 mA cm⁻¹. -2 The time potential only needs to be -0.95 V vs RHE. (From...) Figure 9 As can be seen from b, both the cathode NH3 production and the anode I2 production increase with increasing potential. At a potential of -1.2 V vs RHE, the NO3RR‖IOR cell system produces approximately 2.1 mg / cm³ of NH3. -2 h -1 The I2 production was approximately 0.8 mmol.

[0062] Depend on Figure 10 As can be seen, after a long reaction time of 6 hours (with the cathode electrolyte replaced every 1 hour), the anolyte solution gradually deepened from pale yellow to black. After the resulting solution was allowed to stand at low temperature for a period of time, purplish-black crystals precipitated. Dissolving the crystals in ethanol resulted in a characteristic yellowish-brown solution. XRD characterization of the crystals showed that their characteristic diffraction peaks perfectly matched those of I2 (PDF#43-0304). All these results confirm that the anodic oxidation product is elemental iodine.

Claims

1. A method for preparing a bifunctional nanoflower-like photoelectrocatalytic material, characterized in that, Includes the following steps: 1) Dissolve trisodium citrate in deionized water, add CoCl2 under vigorous stirring to obtain solution A; dissolve Na2WO4 in deionized water to obtain solution B; slowly add solution B to solution A under continuous stirring, and continue stirring for 2 hours to form a uniform pink transparent solution. 2) The pink transparent solution and the pretreated Ti mesh were transferred to an autoclave for hydrothermal reaction. After the reaction was completed, the mixture was allowed to cool naturally to room temperature. The precipitate was collected by centrifugation and washed repeatedly with deionized water. The mixture was then dried overnight in an oven at 60°C to obtain CoWO4 / Ti. 3) Place CoWO4 / Ti and NaH2PO2 into two ceramic boats respectively. Place NaH2PO2 in the upstream zone of the tube furnace and CoWO4 / Ti in the downstream zone, maintaining a distance of 3 cm between them. In a N2 atmosphere, incubate at a rate of 5℃ / min. -1 CoP / CoWO4 / Ti can be obtained by calcining at 350℃ for 2 hours.

2. The preparation method according to claim 1, characterized in that, In step 1), the molar ratio of trisodium citrate, CoCl2 and Na2WO4 is 2:1:

1.

3. The preparation method according to claim 1, characterized in that, In step 2), the hydrothermal reaction is carried out at 200°C for 12 hours.

4. The preparation method according to claim 1, characterized in that, In step 3), the mass ratio of CoWO4 / Ti to NaH2PO2 is 1:

1.

5. The application of the bifunctional nanoflower-like photocatalytic material prepared by the preparation method according to any one of claims 1-4 in the photocatalytic reduction of nitrate to NH3.

6. The application according to claim 5, characterized in that, The application method is as follows: In a standard three-electrode system, a CHI 660E electrochemical workstation was used, with the bifunctional nanoflower-like photoelectrocatalyst material CoP / CoWO4 / Ti as the working electrode, an Ag / AgCl electrode as the reference electrode, a Pt sheet as the counter electrode, a 300 W xenon lamp with λ>420nm as the visible light source, and an argon-saturated neutral mixed electrolyte of 0.5 M Na2SO4 and 0.05 M NaNO3. The voltage was -1.0 V vs RHE, and the photoelectrocatalytic nitrate reduction reaction was carried out.

7. The application of the bifunctional nanoflower-like photoelectrocatalytic material prepared by the preparation method according to any one of claims 1-4 in the electrocatalytic oxidation of iodine.

8. The application according to claim 7, characterized in that, The application method is as follows: A CHI 660E electrochemical workstation was used in a standard three-electrode system. The bifunctional nanoflower-like photoelectrocatalyst CoP / CoWO4 / Ti was used as the working electrode, an Ag / AgCl electrode as the reference electrode, and a Pt sheet as the counter electrode. The electrolyte solution was a mixture of 0.5 M H2SO4 and 0.5 M KI acid-washed electrolyte. A constant stirring frequency of 500 rpm and a current of 15 mA cm⁻¹ were maintained. -2 It undergoes an electrocatalytic iodine oxidation reaction.

9. The application of the bifunctional nanoflower-like photocatalytic material prepared by the preparation method according to any one of claims 1-4 in the photocatalytic co-production of ammonia and iodine.

10. The application according to claim 9, characterized in that, The application method is as follows: A CHI 660E electrochemical workstation is used in an H-type electrolytic cell. The bifunctional nanoflower-like photoelectrocatalytic materials CoP / CoWO4 / Ti are used as the cathode and anode, respectively, and Ag / AgCl is used as the reference electrode. A 300 W xenon lamp with λ>420nm is used as the visible light source to irradiate the cathode. The cathode chamber and anode chamber are separated by a Nafion membrane. The anode electrolyte solution is an acidic mixed solution of 0.5M H2SO4 and 0.5M KI, and the cathode electrolyte solution is a neutral mixed solution of 0.5M Na2SO4 and 0.05M NaNO3. The voltage is -1.2 V vs RHE to carry out photoelectrocatalytic synergistic production of NH3 and I2.

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