Copper-cobalt-loaded ferric oxide composite photocatalyst, preparation method and application of copper-cobalt-loaded ferric oxide composite photocatalyst in hydrogen production by photocatalytic ammonia borane hydrolysis

Abstract

The invention discloses a copper-cobalt-loaded ferric oxide composite photocatalyst, a preparation method and application of the copper-cobalt-loaded ferric oxide composite photocatalyst in hydrogen production by photocatalytic ammonia borane hydrolysis, and belongs to the technical field of photocatalysts. The composite photocatalyst (CuxCoy-alpham-gamman-Fe2O3-R, m + n = 100, x + y = 100, and both x and y are not 0) takes Fe2O3 as a core and copper-cobalt bimetallic nanoparticles reduced by sodium borohydride as an active component, and efficient hydrogen production by ammonia borane hydrolysis is realized through a photocatalysis synergistic effect. The method is simple in synthesis step, small in pollution, low in equipment requirement, mild in reaction condition and easy to implement. Under illumination, strong reducing electrons are generated on the surface of the catalyst, the hydrolysis activation energy is remarkably reduced, the hydrogen production rate reaches 21875 mL.min <-1 >. G <-1 > and is increased by 258% compared with that without illumination, the hydrogen yield can reach 100%, and the activity of the composite photocatalyst is not attenuated after 10 times of circulation after magnetic recovery.

Description

Technical Field

[0001] The present invention belongs to the technical field of photocatalysts, and in particular relates to a copper-cobalt-loaded ferric oxide composite photocatalyst, a preparation method thereof, and application thereof in photocatalytic ammonia borane hydrolysis to produce hydrogen. Background Art

[0002] Ammonia borane (NH3BH3) is an ideal chemical hydrogen storage material due to its high hydrogen storage density (19.6 wt%) and safety. However, its hydrolysis reaction requires an efficient catalyst to release hydrogen under mild conditions. Existing technologies use traditional precious metal catalysts (such as Pt and Ru), which are expensive and difficult to recycle. Non-precious metal catalysts (such as Co and Ni) require high temperatures or strong bases and have poor stability. Photocatalytic technologies can reduce energy consumption, but existing photocatalysts (such as TiO2) have insufficient adsorption and activation capabilities for ammonia borane.

[0003] Magnetic Fe2O3 can simplify catalyst recovery, but the photocatalytic activity of single-phase Fe2O3 is low, and other active components need to be compounded to compensate for this limitation so that it has stronger photocatalytic activity while maintaining its magnetism. Summary of the Invention

[0004] The present invention aims to provide a copper-cobalt loaded composite photocatalyst, a preparation method and its application in photocatalytic ammonia borane hydrolysis to produce hydrogen. The composite photocatalyst (Cu x Co y -α m -γ n -Fe2O3-R, R represents sodium borohydride reduction reaction), and efficient hydrogen production is achieved by hydrolysis of ammonia borane through photocatalytic synergistic effect.

[0005] Innovations of the present invention:

[0006] (1) Bimetallic synergistic effect: The electronic coupling of Cu and Co optimizes the active sites and enhances the adsorption and dissociation ability of ammonia borane;

[0007] (2) Heterogeneous iron oxide forms a heterogeneous junction (α m -γ n- Fe2O3 (m + n = 100, and m and n are not 0): Constructing a heterojunction using the α and γ phases of Fe2O3 can further increase the number of active sites for the catalyst and enhance the separation of photogenerated charges, thereby overcoming the limitations of single Fe2O3 and improving photocatalytic efficiency. The presence of the γ phase can impart excellent magnetic properties to the material, facilitating the recovery of the chemical. In addition, heterojunctions composed of identical atoms overcome the cross-contamination issues of traditional heterojunctions and effectively avoid the stress and impurity issues at the interface of traditional semiconductor-metal junctions, thus providing the opportunity to construct a perfect interface with atomic precision.

[0008] (3) Efficient hydrogen production: Under light, the composite photocatalyst surface generates strong reducing electrons, significantly reducing the activation energy of hydrolysis, and the hydrogen production rate reaches 21875 mL min -1 ·g -1 (i.e. 893mmol·gcat -1 min -1 ), which is a 258% improvement compared to no light.

[0009] The preparation method of the copper-cobalt-supported ferric oxide composite photocatalyst of the present invention comprises the following steps:

[0010] 1) dissolving a trivalent iron salt, urea, and CTAB in a mixed solution of ethylene glycol and water, transferring the solution to a reactor for a high-temperature hydrothermal reaction after ultrasonic treatment and stirring, and cooling the solution to room temperature to obtain an iron oxide solution;

[0011] 2) filtering the iron oxide solution obtained in step 1) to obtain a precipitate, washing the precipitate with water and anhydrous ethanol 3 to 5 times respectively, and then vacuum drying;

[0012] 3) Grinding the dried product of step 2) to obtain α m -γ n -Fe2O3 material, m+n=100;

[0013] 4) The α obtained in step 3) m -γ n -Fe2O3 material is dispersed in deionized water and stirred evenly to obtain α m -γ n -Fe2O3 solution; then add copper salt and cobalt salt thereto, the molar ratio of Cu to Co is x:y, x+y=100, and x and y are not 0; after ultrasonication for a period of time, hot impregnation is performed to obtain a solid product, which is ground and calcined in a muffle furnace to obtain Cu x Co y -α m -γ n -Fe2O3 powder;

[0014] 5) Cu obtained in step 4)x Co y -α m -γ n -Fe2O3 powder was dispersed in deionized water and stirred to obtain Cu x Co y -α m -γ n -Fe2O3 solution, and then reduce it; continue stirring after reduction, and then filter, wash, dry, and grind to obtain the copper-cobalt-loaded ferric oxide composite photocatalyst, denoted as Cu x Co y -α m -γ n -Fe2O3-R, Cu in composite photocatalyst x Co y The loading amount is 15 to 30 wt%.

[0015] The iron salt described in step 1) is one of ferric chloride hexahydrate, ferric nitrate nonahydrate, and ferric acetylacetonate; in the mixed solution, the concentration of iron ions is 0.01 to 0.5 M, the concentration of urea is 0.2 to 5 M, the concentration of CTAB is 0.01 mM to 5 M, and the volume ratio of ethylene glycol to water is 1:0.01 to 10; the temperature of the hydrothermal reaction is 120 to 240 ° C, and the hydrothermal reaction time is 12 to 24 hours;

[0016] In step 2), the filtration is to filter the iron oxide solution with a water pump; the drying temperature is 40 to 80°C;

[0017] In step 4), the copper salt is one of copper nitrate trihydrate, anhydrous copper chloride, copper chloride pentahydrate, and copper acetylacetonate; the cobalt salt is one of cobalt nitrate hexahydrate, cobalt chloride hexahydrate, and cobalt acetylacetonate; the ultrasonication time is 30 to 60 minutes, the hot dipping temperature is 50 to 100° C., and the hot dipping time is 12 to 24 hours; the calcination temperature in the muffle furnace is 200 to 500° C., and the calcination time is 1 to 5 hours;

[0018] The reduction method described in step 5) is to use one of LiBH4 aqueous solution, NaBH4 aqueous solution, a mixed aqueous solution of NaBH4 and NaOH, LiH aqueous solution, and hydrogen reduction; stirring is magnetic stirring at 500-1000 r / min for 1-4 hours.

[0019] Unless otherwise specified, the solvents used in the present invention are all deionized water.

[0020] The copper-cobalt-loaded ferric oxide composite photocatalyst of the present invention is prepared by the above method.

[0021] The present invention discloses a copper-cobalt-loaded ferric oxide composite photocatalyst for the photocatalytic hydrolysis of ammonia borane to produce hydrogen. Ammonia borane and sodium hydroxide are weighed and dissolved in water to form a reaction solution, with a molar ratio of ammonia borane to sodium hydroxide of 1:0.1 to 0.2. The composite photocatalyst is then weighed at a mass ratio of 1:0.5 to 1.5 to sodium hydroxide and placed in an eggplant-shaped liquid-phase reactor with a side branch. The reaction is controlled at room temperature using a constant-temperature water bath and irradiated with visible light from the bottom of the liquid-phase reactor. At the start of the reaction, the reaction solution is rapidly pumped into the liquid-phase reactor. Over time, hydrogen gas is produced within the liquid-phase reactor. The hydrogen is transferred via a rubber tube to an inverted graduated cylinder filled with water. The volume of hydrogen produced is calculated using the displacement method (VH2O is the volume of water displaced, i.e., the volume of hydrogen produced), thereby quantitatively calculating the H2 generation rate. The generation rate is calculated as follows: (nH2·gcat -1 ·t -1 )×100%, where nH2=VH2O / Vm, Vm is generally 24.5L / mol at room temperature; VH2O is the volume of water displaced, divided by 24.5 is to convert the volume of water into moles, gcat -1 The composite photocatalyst of the present invention is used for the first time to photocatalyze the hydrolysis of ammonia borane to produce hydrogen. Under visible light (λ = 400nm to 2500nm), the conversion efficiency of ammonia borane hydrolysis to produce hydrogen is increased by 258%, the hydrogen yield can reach 100%, and the catalyst activity remains unchanged after 10 cycles of magnetic recovery.

[0022] The photocatalyst synthesis process of the present invention is simple. Deionized water is mostly used as the solvent during the preparation process, which reduces pollution, does not require high equipment, and has mild reaction conditions and is easy to implement. Under light, strong reducing electrons are generated on the catalyst surface, significantly reducing the activation energy of hydrolysis and producing hydrogen at a rate of 21875 mL·min -1 ·g -1 , compared to no light, it is improved by 258%. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 :α-Fe2O3、α 78 -γ 22 -Fe2O3, γ-Fe2O3 XRD patterns; 78 -γ 22 -Fe2O3 is a heterogeneous iron oxide with good peak crystallization and no obvious diffraction peak shift;

[0024] Figure 2 : XRD patterns of catalysts prepared in Examples 15-16 with a total metal loading of 20 wt% and the same molar ratio of different metals (wherein the molar ratios Cu:Co=50:50, Cu:Ni=50:50, Co:Ni=50:50); indicating that Cu 50Co 50 -α 78 -γ 22 -Fe2O3-R、Cu 50 Ni 50 -α 78 -γ 22 -Fe2O3-R、Co 50 Ni 50 -α 78 -γ 22 -Fe2O3-R has no obvious diffraction peak shift, and Cu 50 Co 50 -α 78 -γ 22 -Fe2O3-R has the highest peak intensity, indicating that the metal is highly dispersed and successfully incorporated into the support lattice;

[0025] Figure 3 : The comparison chart of hydrogen production rate of the composite photocatalyst prepared in Example 1 under light and no light conditions shows that the hydrogen production rate under light conditions is 893mmol·gcat -1 min -1 , an improvement of 258% compared to no light;

[0026] Figure 4 :α-Fe2O3、α 78 -γ 22 -Fe2O3, γ-Fe2O3 PL images; it shows that the prepared α 78 -γ 22 -Fe2O3 has the highest electron recombination efficiency;

[0027] Figure 5 :α 78 -γ 22 -Fe2O3、Cu 50 Co 50 -α 78 -γ 22 -Fe2O3、Cu 50 Co 50 -α 78 -γ 22 -PL map of Fe2O3-R; it shows that Cu 50 Co 50 -α-γ-Fe2O3-R has the highest electron recombination efficiency;

[0028] Figure 6 : The total metal loading amount prepared in Examples 2 to 7 is 20 wt %, and the α 78 -γ 22-Comparison of hydrogen production rates of Fe2O3 catalysts under light and without light. DETAILED DESCRIPTION

[0029] The following examples are provided to further describe the present invention in detail. The specific operation processes in the examples can help those skilled in the art to more fully understand the present invention. However, the examples do not constitute a limitation of the present invention.

[0030] Example 1

[0031] (1) Prepare a 50mL beaker, weigh 2.70g (0.01mol) of FeCl3·6H2O, 1.80g (0.03mol) of urea and 1.82g (0.005mol) of CTAB, disperse them in a mixed solution of 50mL of ethylene glycol and 50mL of deionized water, ultrasonicate for 5min and stir for 30min, with an ultrasonic power of 100W and a stirring speed of 600r / min. Then transfer the solution to a 100mL reactor, heat it to 200℃ and react for 18h, and cool it to room temperature to obtain an iron oxide solution; then filter the obtained iron oxide solution with a water pump to remove the solution, wash the obtained precipitate with water and anhydrous ethanol three times respectively, and finally dry it in a vacuum drying oven at 60℃; after grinding, obtain α m -γ n -Fe2O3 powder, and X-ray diffraction (XRD) analysis of the γ phase 220 crystal plane and the α phase 104 crystal plane confirmed that the catalyst is α 78 -γ 22 -Fe2O3 powder. X-ray diffraction (XRD) was performed on it, and the results are shown in Figure 1 ;

[0032] (2) Weigh 160 mg of the α obtained in step (1) 78 -γ 22 -Fe2O3 powder was transferred to a 30mL glass bottle, and 3mL of deionized water was added. The mixture was placed on a stirring table and stirred at a speed of 600r / min for 30min to obtain α 78 -γ 22 -Fe2O3 solution;

[0033] (3) Weigh 76.10 mg of copper nitrate trihydrate and 98.8 mg of cobalt nitrate hexahydrate to the α 78 -γ 22 -Fe2O3 solution, ultrasonicated for 30 minutes, and then hot-dipped in a 70℃ oven for 12 hours to obtain a solid product; after grinding for 20 minutes, it was calcined in a muffle furnace at 350℃ for 3 hours to obtain Cu 50 Co 50 -α 78 -γ 22-Fe2O3 powder;

[0034] (4) Weigh 50 mg of Cu in step (3) 50 Co 50 -α 78 -γ 22 -Fe2O3 powder, transfer it to a 30mL glass bottle, add 3mL of deionized water, put it on a stirring table, rotate at 600r / min, stir for 30min, and stir evenly to obtain Cu 50 Co 50 -α 78 -γ 22 -Fe2O3 solution. Weigh 50mg NaBH4 into a small beaker, add 5mL deionized water, sonicate to dissolve it completely, and use a common dropper to slowly drip the sodium borohydride solution into the Cu 50 Co 50 -α 78 γ 22 -Fe2O3 solution, and it was completely dropped in about 10 minutes. After continuing magnetic stirring (800r / min) for 2 hours, the solid was filtered with a water pump and washed with deionized water 4 times, then placed in a vacuum drying oven and dried for 20 hours. After grinding, 20wt% CuCo (molar ratio Cu:Co=50:50) supported α- 78 -γ 22 -Fe2O3 photocatalyst 200mg, named Cu 50 Co 50 -α 78 -γ 22 -Fe2O3-R.

[0035] (5) Weigh 20 mg of Cu in step (4) 50 Co 50 -α 78 -γ 22 -Fe2O3-R photocatalyst, loaded into an eggplant-shaped liquid phase reactor with a side branch. Seal with a threaded rubber stopper, and all interfaces are sealed with vacuum resin. Separately weigh 92.6 mg of ammonia borane solid and 20 mg of sodium hydroxide solid, dissolve them with 2 mL of deionized water, and disperse them by ultrasound to obtain 2 mL of a mixed solution containing 92.6 mg of ammonia borane and 20 mg of sodium hydroxide. Use a syringe to quickly inject the mixed solution of ammonia borane and sodium hydroxide into the reactor, and use a 470 nm LED lamp as a light source placed at the bottom of the reactor to irradiate the photocatalytic ammonia borane hydrolysis hydrogen production reaction. After cooling to room temperature, the volume of hydrogen produced is calculated by the water displacement method (VH2O is the volume of water discharged, that is, the volume of hydrogen produced), thereby quantitatively calculating the generation rate of H2; generation rate = (nH2·gcat -1 ·t -1)×100%, where nH2=VH2O / Vm, Vm is generally 24.5L / mol at room temperature; VH2O is the volume of water displaced, divided by 24.5 is to convert the volume of water into moles, gcat -1 The maximum hydrogen production rate of ammonia borane hydrolysis is 893mmol H2·gcat -1 min -1 , the conversion rate of ammonia borane reached 100%, the results are shown in Figure 3 .

[0036] Example 2

[0037] The preparation and reaction were carried out using the method of Example 1, with the only difference being that only 152.1 mg of copper nitrate trihydrate was weighed in step (3), and the remaining steps remained unchanged. The catalyst synthesized by this method was named Cu 100 -α 78 -γ 22 -Fe2O3-R. The hydrogen production rate of ammonia borane hydrolysis reached 209.264mmol H2·gcat -1 min -1 , the ammonia conversion rate reached 51%, the results are shown Figure 6 .

[0038] Example 3

[0039] The method of Example 1 was used for preparation and reaction, with the only difference being that in step (3) only 150.6 mg of copper nitrate trihydrate and 2.0 mg of cobalt nitrate hexahydrate were weighed, and the other steps remained unchanged. The catalyst synthesized by this method was named Cu 99 Co1-α 78 -γ 22 -Fe2O3-R, the hydrogen production rate of ammonia borane hydrolysis reached 121.753mmol H2·gcat -1 min -1 , the ammonia conversion rate reached 50%, the results are shown Figure 6 .

[0040] Example 4

[0041] The method of Example 1 was used for preparation and reaction, with the only difference being that in step (3) only 134.6 mg of copper nitrate trihydrate and 22.7 mg of cobalt nitrate hexahydrate were weighed, and the other steps remained unchanged. The catalyst synthesized by this method was named Cu 90 Co 10 -α 78 -γ 22 -Fe2O3-R, the hydrogen production rate of ammonia borane hydrolysis reached 291.149mmol H2·gcat -1 min -1, the ammonia conversion rate reached 52.5%, the results are shown in Figure 6 .

[0042] Example 5

[0043] The method of Example 1 was used for preparation and reaction, with the only difference being that in step (3), only 17.5 mg of copper nitrate trihydrate and 174.8 mg of cobalt nitrate hexahydrate were weighed, and the other steps remained unchanged. The catalyst synthesized by this method was named Cu 10 Co 90 -α 78 -γ 22 -Fe2O3-R, the hydrogen production rate of ammonia borane hydrolysis reached 304.383mmol H2·gcat -1 min -1 , the ammonia conversion rate reached 55%, the results are shown Figure 6 .

[0044] Example 6

[0045] The method of Example 1 was used for preparation and reaction, with the only difference being that in step (3) only 1.5 mg of copper nitrate trihydrate and 195.6 mg of cobalt nitrate hexahydrate were weighed, and the remaining steps remained unchanged. The catalyst synthesized by this method was named Cu1Co 99 -α 78 -γ 22 -Fe2O3-R, the hydrogen production rate of ammonia borane hydrolysis reached 230.911mmol H2·gcat -1 min -1 , the ammonia conversion rate reached 55%, the results are shown Figure 6 .

[0046] Example 7

[0047] The method of Example 1 was used for preparation and reaction, with the only difference being that only 197.5 mg of cobalt nitrate hexahydrate was weighed in step (3), and the remaining steps were unchanged. The catalyst synthesized by this method was named Co 100 -α 78 -γ 22 -Fe2O3-R, the hydrogen production rate of ammonia borane hydrolysis reached 155.731mmol H2·gcat -1 min -1 , the ammonia conversion rate reached 57.5%, the results are shown in Figure 6 .

[0048] Example 8

[0049] The preparation and reaction were carried out using the method of Example 1, with the only difference being that light irradiation was not added in step (5), and the other steps remained unchanged. The hydrogen production rate of ammonia borane hydrolysis reached 249.867 mmol H2·gcat-1 min -1 , the ammonia conversion rate reached 100%, the results are shown in Figure 6 .

[0050] Example 9

[0051] The preparation and reaction were carried out using the method of Example 2, with the only difference being that light irradiation was not added in step (5), and the other steps remained unchanged. The hydrogen production rate of ammonia borane hydrolysis reached 48.176 mmol H2·gcat -1 min -1 , the ammonia conversion rate reached 51%, the results are shown Figure 6 .

[0052] Example 10

[0053] The preparation and reaction were carried out using the method of Example 3, with the only difference being that light irradiation was not added in step (5), and the other steps remained unchanged. The hydrogen production rate of ammonia borane hydrolysis reached 80.680 mmol H2·gcat -1 min -1 , the ammonia conversion rate reached 50%, the results are shown Figure 6 .

[0054] Example 11

[0055] The preparation and reaction were carried out using the method of Example 4, with the only difference being that light irradiation was not added in step (5), and the other steps remained unchanged. The hydrogen production rate of ammonia borane hydrolysis reached 126.378 mmol H2·gcat -1 min -1 , the ammonia conversion rate reached 52.5%, the results are shown in Figure 6 .

[0056] Example 12

[0057] The preparation and reaction were carried out using the method of Example 5, with the only difference being that light irradiation was not added in step (5), and the other steps remained unchanged. The hydrogen production rate of ammonia borane hydrolysis reached 81.664 mmol H2·gcat -1 min -1 , the ammonia conversion rate reached 55%, the results are shown Figure 6 .

[0058] Example 13

[0059] The preparation and reaction were carried out using the method of Example 6, with the only difference being that light irradiation was not added in step (5), and the other steps remained unchanged. The hydrogen production rate of ammonia borane hydrolysis reached 55.804 mmol H2·gcat -1 min -1 , the ammonia conversion rate reached 55%, the results are shown Figure 6 .

[0060] Example 14

[0061] The preparation and reaction were carried out using the method of Example 7, with the only difference being that light irradiation was not added in step (5), and the other steps remained unchanged. The hydrogen production rate of ammonia borane hydrolysis reached 48.176 mmol H2·gcat -1 min -1 , the ammonia conversion rate reached 57.5%, the results are shown in Figure 6 .

[0062] Example 15

[0063] The preparation and reaction were carried out using the method of Example 1, with the only difference being that 29.7 g of nickel nitrate hexahydrate and 29.7 g of cobalt nitrate hexahydrate were weighed in step (3), and the remaining steps remained unchanged. The catalyst synthesized by this method was named Co 50 Ni 50 -α 78 -γ 22 -Fe2O3-R, the hydrogen production rate of ammonia borane hydrolysis reached 115.456mmolH2·gcat -1 min -1 , the ammonia conversion rate reached 65%.

[0064] Example 16

[0065] The preparation and reaction were carried out using the method of Example 1, with the only difference being that 24.7 g of copper nitrate trihydrate and 29.7 g of nickel nitrate hexahydrate were weighed in step (3), and the remaining steps remained unchanged. The catalyst synthesized by this method was named Cu 50 Ni 50 -α 78 -γ 22 -Fe2O3-R, the hydrogen production rate of ammonia borane hydrolysis reached 515.110mmolH2·gcat -1 min -1 , the ammonia conversion rate reached 76%.

[0066] Example 17

[0067] (1) Prepare a 50mL beaker, weigh 4.04g (0.01mol) of Fe(NO3)3·9H2O, 1.80g (0.03mol) of urea and 1.82g (0.005mol) of CTAB, disperse them in a mixed solution of 50mL of ethylene glycol and 50mL of deionized water, ultrasonicate for 5min and stir for 30min, with an ultrasonic power of 100W and a stirring speed of 600r / min. Then transfer the solution to a 100mL reactor, heat to 200℃ and react for 18h, cool to room temperature to obtain an iron oxide solution; then filter the obtained iron oxide solution with a water pump to remove the solution, wash the obtained precipitate with water and anhydrous ethanol three times respectively, and finally dry it in a vacuum drying oven at 60℃; after grinding, obtain α m -γ n -Fe2O3 powder, and X-ray diffraction (XRD) analysis of the γ phase 220 crystal plane and the α phase 104 crystal plane confirmed that the catalyst is α 100 -γ0-Fe2O3 powder, namely α-Fe2O3. X-ray diffraction (XRD) was performed on it, and the results are shown in Figure 1 , the remaining steps are the same as Example 1.

[0068] Example 18

[0069] (1) Prepare a 50mL beaker, weigh 6.75g (0.025mol) of FeCl3·6H2O, 1.5g (0.025mol) of urea and 3.6mg (0.01mmol) of CTAB, disperse them in a mixed solution of 59mL of ethylene glycol and 1mL of water, ultrasonicate for 5min and stir for 30min, with an ultrasonic power of 100W and a stirring speed of 600r / min. Then transfer the solution to a 100mL reactor, heat to 200℃ and react for 12h, cool to room temperature to obtain an iron oxide solution; then filter the obtained iron oxide solution with a water pump to remove the solution, wash the obtained precipitate with water and anhydrous ethanol three times respectively, and finally dry it in a vacuum drying oven at 60℃; after grinding, obtain α m -γ n -Fe2O3 powder, and X-ray diffraction (XRD) analysis of the γ phase 220 crystal plane and the α phase 104 crystal plane confirmed that the catalyst is α0-γ 100 -Fe2O3 powder, namely γ-Fe2O3. X-ray diffraction (XRD) was performed on it, and the results are shown in Figure 1 , the remaining steps are the same as Example 1.

[0070] Among them, Examples 2 to 7 prepared composite photocatalysts with a total copper-cobalt loading of 20 wt % and copper-cobalt molar ratios of 100:0, 99:1, 90:10, 50:50, 10:90, 1:99, and 0:100, respectively. After photocatalytic testing, the hydrogen production rates of ammonia borane hydrolysis showed significant contrast, with the copper-cobalt molar ratio of 50:50 being the best, with a hydrogen production rate of up to 893 mmol·gcat -1 min -1 .

[0071] Examples 8 to 14 describe the comparison of hydrogen production rates of photocatalysts under illumination and no illumination conditions, where Cu 50 Co 50 -α 78 -γ 22 -Fe2O3-R composite photocatalyst has a maximum hydrogen production rate of 893mmol·gcat under light conditions -1 min -1 , an improvement of 258% compared to no light.

[0072] Examples 15-16 describe the comparison of hydrogen production rates of composite photocatalysts with a total metal loading of 20 wt % and the same molar ratio of different metals (molar ratio Cu:Co=50:50, Cu:Ni=50:50, Co:Ni=50:50). 50 Co 50 -α 78 -γ 22 -Fe2O3-R composite photocatalyst has the highest hydrogen production rate of 893mmol·gcat -1 min -1 , much higher than those of CuNi and CoNi supported catalysts.

[0073] In general, the results of Examples 1 to 16 show that the total metal loading is 20 wt%, the CuCo molar ratio is 50:50, and the Cu 50 Co 50 -α 78 -γ 22 -Fe2O3-R composite photocatalyst has the highest hydrogen production rate of 893mmol·gcat -1 min -1 .

[0074] Examples 1 and 17-18 show that by adjusting the amount of raw materials and the process parameters during the preparation process, α with different m and n values ​​can be obtained. m -γ n -Fe2O3 powder product. All by α m -γ nThe copper-cobalt-loaded ferric oxide composite photocatalysts prepared by α-Fe2O3 all have photocatalytic effects. 78 -γ 22 -Fe2O3 prepared photocatalyst has the best photocatalytic effect.

Claims

1. A method for preparing a copper-cobalt supported ferric oxide composite photocatalyst, comprising the following steps: 1) dissolving a trivalent iron salt, urea, and CTAB in a mixed solution of ethylene glycol and water, transferring the solution to a reactor for a high-temperature hydrothermal reaction after ultrasonic treatment and stirring, and cooling the solution to room temperature to obtain an iron oxide solution; 2) filtering the iron oxide solution obtained in step 1) to obtain a precipitate, washing the precipitate with water and anhydrous ethanol 3 to 5 times respectively, and then vacuum drying; 3) Grinding the dried product of step 2) to obtain α m -γ n -Fe2O3 material, m+n=100; 4) The α obtained in step 3) m -γ n -Fe2O3 material is dispersed in deionized water and stirred evenly to obtain α m -γ n -Fe2O3 solution; then add copper salt and cobalt salt thereto, the molar ratio of Cu to Co is x:y, x+y=100, and x and y are not 0; after ultrasonication for a period of time, hot impregnation is performed to obtain a solid product, which is ground and calcined to obtain Cu x Co y -α m -γ n -Fe2O3 powder; 5) Cu obtained in step 4) x Co y -α m -γ n -Fe2O3 powder was dispersed in deionized water and stirred to obtain Cu x Co y -α m -γ n -Fe2O3 solution, and then reduce it; continue stirring after reduction, and then filter, wash, dry, and grind to obtain the copper-cobalt-loaded magnetic heterogeneous ferric oxide composite photocatalyst, denoted as Cu x Co y -α m -γ n -Fe2O3-R, Cu in composite photocatalyst x Co y The loading amount is 15 to 30 wt%.

2. The method for preparing a copper-cobalt supported ferric oxide composite photocatalyst according to claim 1, wherein: The iron salt described in step 1) is one of ferric chloride hexahydrate, ferric nitrate nonahydrate, and ferric acetylacetonate; in the mixed solution, the concentration of iron ions is 0.01 to 0.5 M, the concentration of urea is 0.2 to 5 M, the concentration of CTAB is 0.01 mM to 5 M, and the volume ratio of ethylene glycol to water is 1:0.01 to 10; the temperature of the hydrothermal reaction is 120 to 240° C., and the hydrothermal reaction time is 12 to 24 hours.

3. The method for preparing a copper-cobalt supported ferric oxide composite photocatalyst according to claim 1, wherein: In step 2), the copper-cobalt loaded heterogeneous iron oxide solution is filtered by a water pump; the drying temperature is 40-80°C.

4. The method for preparing a copper-cobalt supported ferric oxide composite photocatalyst according to claim 1, wherein: In step 3), m=78, n=22.

5. The method for preparing a copper-cobalt supported ferric oxide composite photocatalyst according to claim 1, wherein: In step 4), the copper salt is one of copper nitrate trihydrate, anhydrous copper chloride, copper chloride pentahydrate, and copper acetylacetonate; the cobalt salt is one of cobalt nitrate hexahydrate, cobalt chloride hexahydrate, and cobalt acetylacetonate; the ultrasonic time is 30 to 60 minutes, the hot dipping temperature is 50 to 100° C., and the hot dipping time is 12 to 24 hours; the calcination temperature is 200 to 500° C., and the calcination time is 1 to 5 hours.

6. The method for preparing a copper-cobalt supported ferric oxide composite photocatalyst according to claim 1, wherein: The reduction method described in step 5) is to use one of LiBH4 aqueous solution, NaBH4 aqueous solution, mixed aqueous solution of NaBH4 and NaOH, LiH aqueous solution or hydrogen reduction; stirring is magnetic stirring at 500-1000 r / min for 1-4 hours.

7. A copper-cobalt supported ferric oxide composite photocatalyst, characterized in that: The compound is prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the copper-cobalt supported magnetic heterogeneous ferric oxide composite photocatalyst according to claim 7 in photocatalytic hydrogen production by hydrolysis of ammonia borane.

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