A NiFe-MMO / NF composite photocatalyst with bicarbonate conversion ability and its application

Abstract

The present invention discloses a NiFe-MMO / NF composite photocatalyst with bicarbonate conversion capability and its application. The composite photocatalyst is prepared by in-situ growing NiFe-LDH on nickel foam NF to obtain a NiFe-LDH / NF precursor. The NiFe-LDH is then topologically converted to NiFe-MMO by calcination, thereby obtaining the NiFe-MMO / NF composite photocatalyst. The NiFe-MMO / NF composite photocatalyst exhibits CO generation activity similar to that of a high-purity CO2 (99.99% by volume) system in the photocatalytic reduction of bicarbonate to carbon monoxide.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparation of micro-nano composite materials, and particularly relates to the preparation of a nano-sheet MMO composite photocatalyst based on nickel foam and its application in photocatalytic reduction of bicarbonate to carbon monoxide. Background Art

[0002] By using clean solar energy, researchers have achieved the conversion of CO₂ into high-energy-density hydrocarbons such as CO, CH₄, and CH₃OH. This not only helps mitigate the increasingly severe greenhouse effect but also provides additional fuels and chemicals, making it a hot topic in environmental chemistry and catalytic chemistry research.

[0003] However, it is still difficult to achieve photocatalytic carbon resource conversion using only CO2 as raw material. For example, the CO2 gas used in the laboratory is usually a high-purity gas (volume fraction of 99.99%) that has been deeply purified. The separation, recovery, and transportation of these high-purity CO2 from the environment will incur high costs, making it difficult for photocatalytic CO2 reduction technology to be popularized. In nature, the types of inorganic carbon resources using CO2 as a medium also include bicarbonate, carbonate, etc. These inorganic carbon resources are cheap, easy to obtain, and widely distributed. How to convert them into useful chemicals will greatly enrich the current photocatalytic CO2 conversion system and have great application prospects.

[0004] At present, layered double hydroxides (also known as hydrotalcites) are reported to be the only natural mineral that can achieve photocatalytic conversion of carbonate / bicarbonate to CO [Journal of the American Chemical Society, 2013, 135(48): 18040-18043]. From a material perspective, hydrotalcites are two-dimensional materials, consisting of positively charged bimetallic layers and negatively charged interlayer anions through electrostatic interaction. From a chemical perspective, when carbonate / bicarbonate is converted to CO, the metal atoms in the layers provide active sites, and the interlayer anions and water provide the reaction raw materials. This catalytic process is affected by the dual effects of the interface morphology and phase structure of the hydrotalcite material. In particular, when the interlayer carbonate / bicarbonate cannot be replenished in time after catalytic conversion, the stability of the hydrotalcite structure will be adversely affected. The in-situ topological transformation of hydrotalcite into the corresponding mixed metal oxides (Mixed Metal Oxides) is considered to be a reliable way to solve this problem [Journal of the American Chemical Society, 2006, 128 (48): 15445-15450]. However, when using conventional pyrolysis methods to achieve the transformation of LDH to MMO, the two-dimensional sheet structure of LDH is prone to agglomeration or collapse, resulting in a decrease in catalytic performance. At the same time, the use of porous materials such as molecular sieves, MOFs, and COFs to inhibit structural collapse often forms a loose MMO-support interface, resulting in a decrease in material stability. How to construct a high-strength LDH-support interface in an integrated manner to achieve the preservation of the sheet morphology and the improvement of catalytic performance when LDH is transformed into MMO is unknown. Summary of the Invention

[0005] One objective of the present invention is to provide a NiFe-MMO / NF composite photocatalyst. This catalyst uses nickel foam (NF) as a carrier and nano-sheet NiFe-MMO as an active component. The two are tightly connected by strong chemical bonds, which improves the structural stability of the photocatalyst. Furthermore, compared to other granular MMO, the sheet-like MMO has a larger specific surface area and more exposed active sites, which helps improve catalytic performance.

[0006] Another object of the present invention is to provide a method for preparing the above-mentioned NiFe-MMO / NF composite photocatalyst, which is suitable for the preparation of MMO / NF composite photocatalysts by topologically transforming LDH / NFs of different metal types, and the preparation method is simple, universal, and the components are flexibly adjustable.

[0007] The third object of the present invention is to provide the use of the above-mentioned composite photocatalyst in the photocatalytic reduction of bicarbonate to carbon monoxide. The catalyst has high activity, greatly enriches the current status of carbon resource conversion, and has broad prospects.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] The first aspect of the present invention provides a NiFe-MMO / NF composite photocatalyst with bicarbonate conversion capability. The composite photocatalyst is prepared by in-situ growing NiFe-LDH on nickel foam NF to obtain a NiFe-LDH / NF precursor, and then topologically converting the NiFe-LDH into NiFe-MMO by calcination, thereby obtaining a NiFe-MMO / NF composite photocatalyst.

[0010] In the NiFe-MMO / NF composite photocatalyst provided by the present invention, NiFe-LDH is first grown in situ on nickel foam, and the two are connected by a strong chemical bond. That is, during the preparation process of NiFe-LDH / NF, the Ni on the surface of nickel foam is etched by acid to generate Ni 2+ , and then with Fe in iron salt 3+ Forming brucite laminae. Next, the NiFe-LDH is calcined. During this process, the strong chemical bond between the nickel foam and the NiFe-LDH ensures a stable morphology. The resulting MMO inherits the nanosheet morphology of the LDH. Compared to other granular MMOs, flake MMOs have a larger specific surface area and more exposed active sites.

[0011] A second aspect of the present invention provides a method for preparing the above-mentioned NiFe-MMO / NF composite photocatalyst, comprising the following steps:

[0012] Step 1: Cut the nickel foam into the required size, wash it with hydrochloric acid, ethanol and deionized water ultrasonically in sequence, and vacuum dry it for use;

[0013] Step 2: dissolving nickel metal salt, iron metal salt and urea in deionized water and stirring to obtain a mixed solution;

[0014] Step 3, adding the nickel foam treated in step 1 to the mixed solution of step 2, and performing a hydrothermal reaction in a closed reactor to obtain a NiFe-LDH / NF precursor;

[0015] Step 4: calcining the NiFe-LDH / NF precursor to obtain a NiFe-MMO / NF composite photocatalyst.

[0016] In the above preparation method of the present invention, nickel metal salt and iron metal salt and a certain amount of urea are dissolved in deionized water to obtain a light yellow solution, and nickel foam is added to the solution to carry out hydrothermal reaction. 2+ and Fe 3+ The hydrolysis of makes the solution acidic. The nickel foam will be etched in the acidic environment, and the Ni 2+ With Fe in solution 3+ Forming brucite laminae. During this process, urea is hydrolyzed and provides an alkali source, which causes the metal ions to form hydroxide precipitation. At this time, the solution becomes a suspension. The suspension product undergoes nucleation and growth steps and eventually becomes LDH nanosheets with good crystallinity, that is, the NiFe-LDH / NF precursor. The precursor is then calcined. NiFe-LDH undergoes the following four steps during the calcination process: (1) removal of surface adsorbed water molecules; (2) removal of interlayer bound water molecules; (3) collapse of the laminar structure and accelerated removal of interlayer bound water molecules; (4) removal of hydroxyl groups in the octahedron of the laminae and transfer of metal ions. Then the NiFe-LDH topology is transformed into NiFe-MMO. In the absence of nickel foam as a carrier, LDH itself has a sheet structure and a large surface energy. During the calcination process, in order to reduce the surface energy, the morphology will agglomerate, that is, granular MMO is obtained. In NiFe-LDH / NF, due to the strong chemical bond between nickel foam and LDH, the structural stability is improved during the calcination process, that is, flaky MMO can be obtained.

[0017] Compared to the previously reported method of converting LDH to MMO by calcining, the present invention first in situ grows NiFe-LDH on nickel foam, then directly calcines the NiFe-LDH / NF precursor to produce a flake-like composite photocatalyst of MMO and nickel foam. This method solves the problem of NiFe-LDH nanosheets agglomerating during the calcination process to reduce their high surface energy, which can lead to surface energy reduction.

[0018] Preferably, the concentration of hydrochloric acid used in step 1 is 0.5 to 2 mol / L, and the ultrasonic time is 5 to 15 min.

[0019] Preferably, in step 2, the molar ratio of the nickel metal salt to the iron metal salt is 2-4:1, and the molar ratio of the total molar amount of the nickel metal salt and the iron metal salt to the urea is 1:2-4.

[0020] Preferably, in step 2, the nickel metal salt is at least one of nickel nitrate, nickel sulfate and nickel chloride, and the iron metal salt is at least one of ferric nitrate, ferric sulfate and ferric chloride.

[0021] Preferably, in step 3, the reaction temperature of the hydrothermal reaction is 80-150° C., and the reaction time is 8-20 h.

[0022] Preferably, in step 4, the calcination temperature is 200-500° C., the calcination time is 4-8 hours, and the heating rate is 1-5° C. / min.

[0023] The third aspect of the present invention is to provide the use of the composite photocatalyst in photocatalytic reduction of bicarbonate to carbon monoxide.

[0024] In the process of photocatalytic conversion of bicarbonate to carbon monoxide, there are two ways of converting bicarbonate: one is the self-hydrolysis of bicarbonate to produce CO2, followed by a photocatalytic reduction reaction of CO2 to CO; the other is the generation of protons during the photooxidation of a sacrificial agent (triethanolamine (TEOA)), which combines with bicarbonate to produce carbonic acid and then decomposes into CO2, followed by a photocatalytic reduction reaction of CO2 to CO. For the composite photocatalyst of the present invention, the nickel foam has a three-dimensional porous network structure, which is conducive to the diffusion and adsorption of bicarbonate. Nano-sheet MMO is also conducive to the adsorption of bicarbonate due to its large specific surface area. At the same time, sheet MMO has more exposed active sites than other granular MMO, which promotes its photocatalytic reduction of bicarbonate to carbon monoxide activity. Therefore, the photocatalyst synthesized by the present invention focuses on the integration of nano-sheet MMO and photocatalytic conversion of bicarbonate to carbon monoxide, which is promising in practical applications.

[0025] The catalyst provided by the present invention exhibits excellent performance in the photocatalytic reduction of bicarbonate to carbon monoxide. In a system of sodium bicarbonate (NaHCO3), ruthenium bipyridine (Ru(bpy)3Cl2·6H2O), triethanolamine (TEOA), and water, the composite photocatalyst achieves a CO yield of 2.07 μmol·h under full-spectrum illumination conditions. -1 , and showed similar performance to the high-purity CO2 (volume fraction of 99.99%) system under this condition.

[0026] The beneficial effects of the present invention are embodied in:

[0027] 1. The NiFe-MMO / NF composite photocatalyst provided by the present invention has a nickel foam substrate and an active component of nano-sheet NiFe-MMO, which is a new type of MMO-based photocatalyst.

[0028] 2. The NiFe-MMO / NF composite photocatalyst proposed in this invention is based on the in situ growth of NiFe-LDH on nickel foam. The precursor is then calcined to produce nanosheet-shaped MMO. The strong chemical bond between the LDH and nickel foam maintains the structural stability of the composite. This preparation method is universally applicable to the synthesis of a variety of LDH-to-MMO photocatalysts for topological conversion.

[0029] 3. In the composite photocatalyst of the present invention, due to the large specific surface area and multiple exposed active sites of the nanosheet-shaped MMO, the NiFe-MMO / NF composite photocatalyst has a CO generation activity similar to that of a high-purity CO2 (volume fraction of 99.99%) system in the application of photocatalytic reduction of bicarbonate to carbon monoxide. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0031] Figure 1 A schematic diagram showing the morphology and structure of the NiFe-MMO / NF composite catalyst obtained in the present invention is shown.

[0032] Figure 2 The XRD pattern of the NiFe-LDH catalyst obtained in Example 1 of the present invention is shown.

[0033] Figure 3 The XRD pattern of the NiFe-LDH / NF composite catalyst obtained in Example 1 of the present invention is shown.

[0034] Figure 4 The XRD pattern of the NiFe-MMO catalyst obtained in Example 1 of the present invention is shown.

[0035] Figure 5 The XRD pattern of the NiFe-MMO / NF composite catalyst obtained in Example 1 of the present invention is shown.

[0036] Figure 6 The SEM images of the NiFe-LDH / NF composite catalyst obtained in Example 1 of the present invention are shown, wherein a) to d) correspond to different magnifications.

[0037] Figure 7 The SEM images of the NiFe-MMO / NF composite catalyst obtained in Example 1 of the present invention are shown, wherein a) to d) correspond to different magnifications.

[0038] Figure 8 The XRD pattern of the NiFe-LDH catalyst obtained in Comparative Example 1 of the present invention is shown.

[0039] Figure 9The XRD pattern of the NiFe-MMO catalyst obtained in Comparative Example 1 of the present invention is shown.

[0040] Figure 10 The SEM spectrum of the NiFe-LDH catalyst obtained in Comparative Example 1 of the present invention is shown.

[0041] Figure 11 The SEM spectrum of the NiFe-MMO catalyst obtained in Comparative Example 1 of the present invention is shown.

[0042] Figure 12 The XRD pattern of the NF obtained in Comparative Example 2 of the present invention is shown.

[0043] Figure 13 The SEM images of the NF obtained in Comparative Example 2 of the present invention are shown, wherein a) to d) correspond to different magnifications.

[0044] Figure 14 The performance graph shows the NiFe-MMO / NF composite photocatalyst prepared in Example 1 of the present invention and the NiFe-MMO prepared in Comparative Example 1 applied to the photocatalytic reduction of bicarbonate to carbon monoxide. DETAILED DESCRIPTION

[0045] To make the above-mentioned objects, features, and advantages of the present invention more readily understood, the following detailed description of the specific embodiments of the present invention is provided in conjunction with the accompanying drawings. The following is merely an example and illustration of the concept of the present invention. Persons skilled in the art may make various modifications, additions, or substitute similar methods for the specific embodiments described. These modifications, additions, or substitutions to the specific embodiments described herein, without departing from the concept of the invention or exceeding the scope defined by the claims, shall fall within the scope of protection of the present invention.

[0046] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0047] Unless otherwise specified, the reagents and materials used in the following examples can be obtained from commercial sources.

[0048] Example 1

[0049] A method for preparing a NiFe-MMO / NF composite photocatalyst comprises the following steps:

[0050] Step 1: Cut the nickel foam into 2cm×2cm size and use a concentration of 1mol·L -1 The product was ultrasonically washed with hydrochloric acid for 5 min, followed by ultrasonic washing with ethanol and deionized water for 10 min in sequence, and finally dried in a vacuum drying oven at 60°C for 12 h before use.

[0051] Step 2: Weigh 0.4365 g (1.5 mmol) of nickel nitrate hexahydrate, 0.202 g (0.5 mmol) of ferric nitrate nonahydrate, and 0.3 g (5 mmol) of urea, add 30 mL of deionized water, and stir magnetically until completely dissolved to obtain a light yellow solution. Transfer the solution to the lining of the reactor.

[0052] Step 3: Add the nickel foam obtained in step 1 to the light yellow solution obtained in step 2, disperse under ultrasonication for 15 minutes, and then react at 120° C. for 12 hours. Then, cool the reactor to room temperature.

[0053] The obtained solid product not grown on the nickel foam was centrifugally washed five times with ethanol and deionized water in sequence. The washing liquid was colorless and transparent when poured out. The remaining solid was dried at 60° C. for 24 h to obtain NiFe-LDH.

[0054] The obtained nickel foam with solid product was washed five times with ethanol and deionized water in sequence. The washing liquid was poured out to be colorless and transparent. The nickel foam was vacuum dried at 60° C. for 24 h to obtain NiFe-LDH / NF.

[0055] Step 4: The NiFe-LDH and NiFe-LDH / NF obtained above were calcined in an air atmosphere at 275°C for 5 h (heating rate of 1°C / min), and then cooled to room temperature to obtain NiFe-MMO and NiFe-MMO / NF.

[0056] Figure 2 The XRD pattern of the NiFe-LDH catalyst obtained in Example 1 of the present invention is shown. In the figure, the specific crystal planes (003), (006), and (009) of LDH can be observed, confirming the successful synthesis of LDH.

[0057] Figure 3 The XRD pattern of the NiFe-LDH / NF composite catalyst obtained in Example 1 is shown. In the figure, only the diffraction peak of NF can be observed, but not the diffraction peak of LDH. The main reason is that the diffraction peak of NF is too strong, making the diffraction peak of LDH difficult to observe.

[0058] Figure 4 The XRD pattern of the NiFe-MMO catalyst obtained in Example 1 of the present invention is shown. In the figure, the diffraction peak of NiFe-MMO can be observed, confirming the successful synthesis of NiFe-MMO, that is, the topological transformation of NiFe-LDH into NiFe-MMO.

[0059] Figure 5The XRD pattern of the NiFe-MMO / NF composite catalyst obtained in Example 1 is shown. In the figure, only the diffraction peak of NF is observed, but not the diffraction peak of NiFe-MMO. The main reason is that the diffraction peak of NF is too strong, making the diffraction peak of NiFe-MMO difficult to observe.

[0060] Figure 6 The SEM image of the NiFe-LDH / NF composite catalyst obtained in Example 1 of the present invention is shown. As can be seen from the figure, the nickel foam has a three-dimensional porous network structure, and the LDH has a nanoflower morphology, and the nanoflower is composed of LDH nanosheets.

[0061] Figure 7 The SEM image of the NiFe-MMO / NF composite catalyst obtained in Example 1 of the present invention is shown. As can be seen from the figure, NiFe-MMO / NF and NiFe-LDH / NF exhibit identical morphologies, with the NiFe-MMO also presenting nanoflowers composed of nanosheets. This confirms that nickel foam maintains the morphological stability of NiFe-LDH during calcination.

[0062] Example 2

[0063] A method for preparing a NiFe-MMO / NF composite photocatalyst comprises the following steps:

[0064] Step 1: Cut the nickel foam into 2cm×2cm size and use a concentration of 1mol·L -1 The samples were ultrasonically washed with hydrochloric acid for 5 min, followed by ultrasonic washing with ethanol and deionized water for 10 min, and finally dried in a vacuum drying oven at 60°C for 12 h before use.

[0065] Step 2: Weigh 0.291 g (1.0 mmol) of nickel nitrate hexahydrate, 0.202 g (0.5 mmol) of ferric nitrate nonahydrate, and 0.3 g (5 mmol) of urea, add 30 mL of deionized water, and stir magnetically until completely dissolved to obtain a light yellow solution. Transfer the solution to the lining of the reactor.

[0066] Step 3: Add the nickel foam obtained in step 1 to the light yellow solution obtained in step 2, disperse under ultrasonication for 15 minutes, and then react at 120° C. for 12 hours. Then, cool the reactor to room temperature.

[0067] The obtained nickel foam with solid product grown thereon was washed five times with ethanol and deionized water in sequence. The washing liquid was then poured out to be colorless and transparent. The nickel foam was vacuum dried at 60° C. for 24 h to obtain NiFe-LDH / NF.

[0068] Step 4: calcining the NiFe-LDH / NF obtained above at 275°C for 5 h (heating rate of 1°C / min) in an air atmosphere, and then cooling to room temperature to obtain NiFe-MMO / NF.

[0069] Example 3

[0070] A method for preparing a NiFe-MMO / NF composite photocatalyst comprises the following steps:

[0071] Step 1: Cut the nickel foam into 2cm×2cm size and use a concentration of 1mol·L -1 The samples were ultrasonically washed with hydrochloric acid for 5 min, followed by ultrasonic washing with ethanol and deionized water for 10 min, and finally dried in a vacuum drying oven at 60°C for 12 h before use.

[0072] Step 2: Weigh 0.582 g (2 mmol) of nickel nitrate hexahydrate, 0.202 g (0.5 mmol) of ferric nitrate nonahydrate, and 0.3 g (5 mmol) of urea, add 30 mL of deionized water, and stir magnetically until completely dissolved to obtain a light yellow solution. Transfer the solution to the lining of the reactor.

[0073] Step 3: Add the nickel foam obtained in step 1 to the light yellow solution obtained in step 2, disperse under ultrasonication for 15 minutes, and then react at 120° C. for 12 hours. Then, cool the reactor to room temperature.

[0074] The obtained nickel foam with solid product grown thereon was washed five times with ethanol and deionized water in sequence. The washing liquid was then poured out to be colorless and transparent. The nickel foam was vacuum dried at 60° C. for 24 h to obtain NiFe-LDH / NF.

[0075] Step 4: calcining the NiFe-LDH / NF obtained above at 275°C for 5 h (heating rate of 1°C / min) in an air atmosphere, and then cooling to room temperature to obtain NiFe-MMO / NF.

[0076] Comparative Example 1

[0077] The synthesis of NiFe-MMO material includes the following steps:

[0078] Step 1. Weigh 0.4365 g (1.5 mmol) of nickel nitrate hexahydrate, 0.202 g (0.5 mmol) of ferric nitrate nonahydrate, and 0.3 g (5 mmol) of urea, add 30 mL of deionized water, and stir magnetically until completely dissolved to obtain a light yellow solution. Transfer the solution to the lining of the reactor, then react at 120 ° C for 12 hours, cool the reactor to room temperature, and wash the obtained solid product with ethanol and deionized water by centrifugation 5 times in sequence. At this time, the washing liquid is colorless and transparent when poured out, and the remaining solid is dried at 60 ° C for 24 hours to obtain NiFe-LDH.

[0079] Step 2: calcining the NiFe-LDH obtained above at 275° C. for 5 h (heating rate of 1° C. / min) in an air atmosphere, and then cooling to room temperature to obtain NiFe-MMO.

[0080] Figure 8 The XRD pattern of the NiFe-LDH catalyst obtained in Comparative Example 1 of the present invention is shown. In the figure, it can be observed that the specific crystal planes of LDH are (003), (006), and (009), confirming the successful synthesis of LDH.

[0081] Figure 9 The XRD pattern of the NiFe-MMO catalyst obtained in Comparative Example 1 of the present invention is shown. In the figure, the diffraction peak of NiFe-MMO can be observed, confirming the successful synthesis of NiFe-MMO, that is, the topological transformation of NiFe-LDH into NiFe-MMO.

[0082] Figure 10 The SEM image of the NiFe-LDH catalyst obtained in Comparative Example 1 of the present invention is shown. As can be seen from the figure, the morphology of LDH is agglomerated flakes, confirming the successful synthesis of LDH.

[0083] Figure 11 The SEM image of the NiFe-MMO catalyst obtained in Comparative Example 1 of the present invention is shown. As can be seen from the figure, the morphology of MMO is agglomerated particles, confirming the successful preparation of MMO and also proving that the nickel foam carrier plays a role in maintaining the flaky morphology of hydrotalcite.

[0084] Comparative Example 2

[0085] The synthesis of nickel foam material includes the following steps:

[0086] The nickel foam was cut into 2 cm × 2 cm size and the concentration was 1 mol·L -1 The samples were ultrasonically washed with hydrochloric acid for 5 min, then ultrasonically washed with ethanol and deionized water for 10 min each, and finally dried in a vacuum drying oven at 60°C for 12 h before use, which was recorded as NF.

[0087] Figure 12 The XRD pattern of the NF obtained in Comparative Example 2 of the present invention is shown. In the figure, obvious diffraction peaks of the NF can be observed.

[0088] Figure 13The SEM image of the NF obtained in Comparative Example 2 of the present invention is shown. As can be seen from the figure, the morphology of the nickel foam is a smooth three-dimensional porous network structure, which is significantly different from the morphology of the NiFe-LDH / NF composite catalyst and the NiFe-MMO / NF composite catalyst in Example 1, confirming the successful synthesis of the composite catalyst.

[0089] Test Example 1

[0090] The NiFe-MMO / NF composite photocatalyst prepared in Example 1 and the NiFe-MMO catalyst prepared in Comparative Example 1 were used to photocatalytically reduce bicarbonate / high-purity CO2 (volume fraction 99.99%) to carbon monoxide.

[0091] Cut NiFe-MMO / NF into 2mm×8mm size, weigh 2mgNiFe-MMO: a. Disperse them separately in a special reactor filled with 6mL deionized water, and add 4mL TEOA and 3mg Ru(bpy)3Cl2·6H2O, and disperse them evenly with ultrasound; introduce the corresponding CO2 gas into the solution to keep the reaction system filled with high concentration of CO2, the ventilation time is 20min, and the ventilation rate is 30mL / min. b. Disperse them separately in a special reactor filled with 6mL of 0.2mol·L -1 Sodium bicarbonate solution was prepared, and 4 mL TEOA and 3 mg Ru(bpy)3Cl2·6H2O were added, and ultrasonic dispersion was performed uniformly. Argon was introduced into the solution to exhaust the air in the reactor.

[0092] The above two solutions were tested for photocatalysis using a xenon lamp light source, with a current of 10A and an illumination time of 2 hours. 0.5 mL of gas was then extracted using a sampling needle and injected into a gas chromatograph for quantitative analysis to obtain the photocatalytic activity of reducing bicarbonate to carbon monoxide, as shown in Figure 2. Figure 14 As shown in the figure, it can be seen that for the NiFe-MMO / NF composite photocatalyst, the photocatalytic activity of reducing bicarbonate to carbon monoxide is 2.07 μmol·h -1 , and showed similar performance to the high-purity CO2 system under this condition; for NiFe-MMO, it showed a photocatalytic activity of 0.36 μmol·h -1 , which is quite different from the high-purity CO2 system under this condition. This shows the superiority of the NiFe-MMO / NF composite photocatalyst prepared in Example 1 in photocatalytic reduction of bicarbonate to carbon monoxide.

[0093] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. Application of a NiFe-MMO / NF composite photocatalyst in the photocatalytic reduction of bicarbonate to carbon monoxide, characterized by: The photocatalytic reaction of reducing bicarbonate to carbon monoxide is carried out in a system of bicarbonate, ruthenium bipyridine Ru(bpy)3Cl2·6H2O, triethanolamine (TEOA), and water. The composite photocatalyst is prepared by in-situ growing NiFe-LDH on nickel foam NF to obtain a NiFe-LDH / NF precursor, and then topologically converting the NiFe-LDH into NiFe-MMO by calcination to obtain a NiFe-MMO / NF composite photocatalyst.

2. The use according to claim 1, characterized in that: The NiFe-MMO in the composite photocatalyst has a nanosheet morphology.

3. The use according to claim 1, characterized in that: The preparation method of the NiFe-MMO / NF composite photocatalyst comprises the following steps: Step 1: Cut the nickel foam into the required size, wash it with hydrochloric acid, ethanol and deionized water ultrasonically in sequence, and vacuum dry it for use; Step 2: dissolving nickel metal salt, iron metal salt and urea in deionized water and stirring to obtain a mixed solution; Step 3, adding the nickel foam treated in step 1 to the mixed solution of step 2, and performing a hydrothermal reaction in a closed reactor to obtain a NiFe-LDH / NF precursor; Step 4: calcining the NiFe-LDH / NF precursor to obtain a NiFe-MMO / NF composite photocatalyst.

4. The use according to claim 3, characterized in that: The concentration of hydrochloric acid used in step 1 is 0.5-2 mol / L, and the ultrasonication time is 5-15 min.

5. The use according to claim 3, characterized in that: In step 2, the molar ratio of the nickel metal salt to the iron metal salt is 2-4:1, and the molar ratio of the total molar amount of the nickel metal salt and the iron metal salt to the urea is 1:2-4.

6. The use according to claim 3, characterized in that: In step 2, the nickel metal salt is at least one of nickel nitrate, nickel sulfate and nickel chloride, and the iron metal salt is at least one of ferric nitrate, ferric sulfate and ferric chloride.

7. The use according to claim 3, characterized in that: In step 3, the reaction temperature of the hydrothermal reaction is 80-150° C., and the reaction time is 8-20 h.

8. The use according to claim 3, characterized in that: In step 4, the calcination temperature is 200-500°C, the calcination time is 4-8 h, and the heating rate is 1-5°C / min.

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