Zinc cobaltate heterojunction composite material and preparation method and application thereof

Abstract

The invention relates to the technical field of photocatalysts, in particular to a zinc cobaltate heterojunction composite material and a preparation method and application thereof. The zinc cobaltate heterojunction composite material is prepared by taking tubular graphite phase C3N4 as a carrier, and grinding and compounding the tubular graphite phase C3N4 and zinc cobaltate to enable the zinc cobaltate to be attached to the tubular graphite phase C3N4; the addition amount of the zinc cobaltate accounts for 1-8% of the total mass of the mixture of the tubular graphite phase C3N4 and the zinc cobaltate. According to the zinc cobaltate heterojunction composite material disclosed by the invention, an energy barrier is formed near a heterojunction interface, free compounding of electrons and holes is limited, so that the electrons and the holes are easier to separate in a heterojunction region, and the compounding possibility is reduced, so that the photocatalytic performance is improved. The zinc cobaltate heterojunction composite material disclosed by the invention can be used as a photocatalyst to be applied to the aspect of synergistic hydrogen production.

Description

Technical Field

[0001] The present invention relates to the technical field of photocatalysts, and in particular to a zinc cobaltate heterojunction composite material and a preparation method and application thereof. Background Art

[0002] In recent years, photocatalytic technology has shown broad application prospects in the fields of clean energy production and environmental pollution control.

[0003] Spinel-type composite metal oxides, represented by zinc cobalt oxides, such as ZnCo2O4, have attracted widespread attention in the field of photocatalytic hydrogen production due to their unique band structure and photoresponsive properties. To improve the photocatalytic efficiency of zinc cobalt oxide, researchers have attempted to construct heterojunction composites by combining zinc cobalt oxide with other semiconductor materials to achieve effective separation of photogenerated electrons and holes, thereby improving photocatalytic performance.

[0004] Patent application CN111644188 A discloses a ZnCo2O4 / g-C3N4 composite material. By loading ZnCo2O4 nanoparticles onto the surface of graphite-phase carbon nitride (g-C3N4), the composite material is used for the photocatalytic degradation of antibiotic wastewater, including norfloxacin. Although the ZnCo2O4 / g-C3N4 composite material exhibits some activity in the degradation of antibiotic pollutants, the graphite-phase carbon nitride (g-C3N4) particles used are blocky. Blocky g-C3N4 exhibits defects such as long electron-hole pair transport paths, easy recombination within the bulk phase, and insufficient exposure of active sites. Summary of the Invention

[0005] In order to solve the problems in the prior art of preparing ZnCo2O4 / g-C3N4 composite materials, such as the use of blocky g-C3N4, which leads to a long electron-hole pair transmission path, easy recombination in the bulk phase, and insufficient exposure of active sites, the present invention provides a zinc cobaltate heterojunction composite material, a preparation method and application thereof.

[0006] To achieve the above objectives, the technical solutions of the present invention are as follows.

[0007] A first aspect of the present invention provides a zinc cobaltate heterojunction composite material. The zinc cobaltate heterojunction composite material is prepared by grinding and compounding the tubular graphite phase C3N4 and zinc cobaltate so that the zinc cobaltate adheres to the tubular graphite phase C3N4. The amount of zinc cobaltate added accounts for 1% to 8% of the total mass of the mixture of the tubular graphite phase C3N4 and the zinc cobaltate.

[0008] The present invention primarily utilizes tubular graphite phase C3N4 as a carrier and grinds and composites it with zinc cobaltate, thereby attaching the zinc cobaltate to the tubular graphite phase C3N4. This produces a zinc cobaltate heterojunction composite material. Due to the unique structure of the tubular graphite phase C3N4, the prepared zinc cobaltate heterojunction composite material exhibits excellent light scattering, facilitating directional carrier transfer. Simultaneously, the expanded specific surface area effectively enhances photocatalytic performance, overcoming the issues of bulk g-C3N4-based composite materials, such as volumetric morphological aggregation, limited active sites, low light absorbance, and slow charge separation / transfer, resulting in mediocre performance in photocatalytic degradation and water splitting. The tubular graphite phase C3N4 exhibits a larger surface area and excellent photocatalytic hydrogen production performance, with a hydrogen production rate 217.9 μmol / g / h higher than that of bulk carbon nitride.

[0009] Preferably, the diameter of the tubular graphite phase C3N4 is 2 μm to 3 μm; the diameter of the zinc cobaltate is 5 μm to 6 μm; and the amount of zinc cobaltate added is 1% to 8% of the total mass of the mixture of the tubular graphite phase C3N4 and zinc cobaltate. Further preferably, the amount of zinc cobaltate added is 6% of the total mass of the mixture of the tubular graphite phase C3N4 and zinc cobaltate.

[0010] A second aspect of the present invention provides a method for preparing the zinc cobaltate heterojunction composite material according to the first aspect, comprising the following steps:

[0011] The tubular graphite phase C3N4 and zinc cobaltate are ground and composited so that the zinc cobaltate is attached to the tubular graphite phase C3N4 to obtain a zinc cobaltate heterojunction composite material.

[0012] Preferably, the grinding and compounding is carried out by wet grinding, and the medium of wet grinding is water and ethanol.

[0013] Preferably, after grinding and compounding, drying is further included, and the drying temperature is 50-65°C.

[0014] Preferably, the tubular graphite phase C3N4 is prepared by the following method:

[0015] After stirring and mixing melamine, an acid catalyst and water, a hydrothermal reaction is carried out at 170°C to 190°C to cause a condensation reaction between melamine molecules to form a supramolecular precursor; the supramolecular precursor is calcined at 450°C to 600°C to cause thermal decomposition and reconstruction of the supramolecular precursor to form a tubular graphite phase C3N4.

[0016] Preferably, the acid catalyst is phosphoric acid, and the concentration of phosphoric acid is ≥99%.

[0017] Preferably, the mass ratio of melamine to acid catalyst is 3:1-3;

[0018] The usage ratio of melamine and water is 3g:70mL~100mL.

[0019] The third aspect of the present invention provides an application of the zinc cobaltate heterojunction composite material described in the first aspect as a photocatalyst for synergistic hydrogen production.

[0020] Preferably, the specific application method is:

[0021] The photocatalyst, the Pt co-catalyst and the sacrificial agent are uniformly mixed in a buffer solution system, and then photocatalytic synergistic hydrogen production is carried out under light conditions; the mass ratio of the photocatalyst, the Pt co-catalyst and the sacrificial agent is 5 mg: 0.5 mg~1 mg: 0.1 g~0.2 g; and the dosage ratio of the photocatalyst to the buffer solution is 1 mg: 1 mL~5 mL.

[0022] The Pt promoter is potassium chloroplatinite with a purity of 98%.

[0023] The sacrificial agent is any one of EDTA-2Na, tetracycline, amoxicillin, ciprofloxacin, gentamicin sulfate, sulfamethazine, oxytetracycline and cephalexin.

[0024] The buffer solution is a mixed solution of acetic acid and sodium acetate, with a pH of 5 to 6. In the buffer solution, the molar ratio of acetic acid to sodium acetate is 43.2:156-157, specifically 43.189:156.811.

[0025] Beneficial effects of the present invention:

[0026] 1. The present invention primarily utilizes tubular graphite phase C3N4 as a carrier and grinds and composites it with zinc cobaltate, thereby attaching the zinc cobaltate to the tubular graphite phase C3N4 to prepare a zinc cobaltate heterojunction composite material. Due to the unique structure of the tubular graphite phase C3N4, the prepared zinc cobaltate heterojunction composite material exhibits excellent light scattering ability, facilitating directional carrier transfer. Simultaneously, the expanded specific surface area effectively enhances photocatalytic performance, addressing the issues of bulk g-C3N4-based composite materials that suffer from bulk morphological aggregation, limited active sites, low light absorbance, and slow charge separation / transfer, resulting in mediocre performance in photocatalytic degradation and water splitting.

[0027] 2. The present invention grinds and compounds the tubular graphite phase C3N4 with zinc cobaltate. During the grinding and compounding process, the zinc cobaltate adheres to the tubular graphite phase C3N4 to form a zinc cobaltate heterojunction composite material. The zinc cobaltate heterojunction composite material of the present invention forms an energy barrier near the heterojunction interface, which limits the free recombination of electrons and holes, making it easier for electrons and holes to separate in the heterojunction region, reducing the possibility of recombination, and thus improving the photocatalytic performance.

[0028] 3. The zinc cobaltate heterojunction composite material of the present invention can be used as a photocatalyst to cooperate with a Pt co-catalyst and a sacrificial agent to perform photocatalytic synergistic hydrogen production, and exhibits relatively high synergistic hydrogen production performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 1 is the X-ray diffraction pattern of the zinc cobaltate heterojunction composite material prepared in Examples 1 to 5.

[0030] Figure 2 These are the N2 adsorption-desorption isotherms of tubular g-C3N4 and bulk g-C3N4.

[0031] Figure 3 It is the pore size distribution diagram of tubular g-C3N4 and bulk g-C3N4.

[0032] Figure 4 This is a comparison chart of the hydrogen production rates of the zinc cobaltate heterojunction composite materials prepared in Examples 1 to 5, as well as zinc cobaltate, tubular g-C3N4 and bulk g-C3N4 as photocatalysts when EDTA-2Na is used as a sacrificial agent.

[0033] Figure 5 This is a comparison chart of the hydrogen production rates of the zinc cobaltate heterojunction composite material prepared in Example 4 when different antibiotics are used as sacrificial agents as photocatalysts.

[0034] Figure 6 This is a comparison chart of the hydrogen production rate of tubular g-C3N4 prepared as a catalyst when different antibiotics are used as sacrificial agents. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0036] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of the present invention.

[0037] Patent application CN111644188 A discloses a ZnCo2O4 / g-C3N4 composite material. ZnCo2O4 nanoparticles are loaded onto the surface of graphitic carbon nitride (g-C3N4) for photocatalytic degradation of antibiotic wastewater, including norfloxacin. However, the graphitic carbon nitride (g-C3N4) particles used are flaky, which has drawbacks such as long electron-hole pair transport paths, easy recombination within the bulk phase, and insufficient exposure of active sites.

[0038] In order to solve the above problems, the present invention uses tubular graphite phase carbon nitride. The unique tubular structure of tubular graphite phase carbon nitride can promote the directional transfer of carriers and effectively solve the inherent defects in bulk g-C3N4.

[0039] Currently, there is a lack of bifunctional catalyst materials that can effectively achieve both photocatalytic hydrogen production and antibiotic wastewater degradation. The evolution of photocatalytic hydrogen production always involves the consumption of sacrificial agents. While the presence of sacrificial agents can allow more electrons to participate in hydrogen production, more research is needed to explore whether using sacrificial agents for hydrogen production is economically feasible. Furthermore, some organic sacrificial agents, such as methanol, ethanol, and lactic acid, also serve as energy or fuel. Therefore, the present invention uses antibiotics as sacrificial agents, degrading the sacrificial agents while simultaneously promoting the generation of clean H2, turning waste into valuable resources.

[0040] The technical solution of the present invention is further described below through specific embodiments.

[0041] In the following examples, the methods described are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified.

[0042] Graphitic carbon nitride, denoted as g-C3N4. Tubular graphite C3N4, denoted as tubular g-C3N4. Zinc cobalt oxide, denoted as ZnCo2O4. The diameter of the tubular graphite C3N4 is 2 to 3 μm; the diameter of the zinc cobalt oxide is 5 to 6 μm.

[0043] The purity of melamine is ≥99.8%. The purity of phosphoric acid is ≥99%. The purity of potassium chloroplatinite is 98%.

[0044] Example 1

[0045] A method for preparing a zinc cobaltate heterojunction composite material comprises the following steps:

[0046] Step 1, preparation of tubular g-C3N4:

[0047] 3g of melamine and 1g of phosphoric acid were added to 70mL of water and stirred vigorously for 30 minutes to obtain a mixed solution. The mixed solution was transferred to a 100mL stainless steel autoclave with a polytetrafluoroethylene liner and reacted at 180°C for 10 hours. After the reaction, the mixture was washed with water until the phosphoric acid was completely removed and then dried at 60°C to obtain a supramolecular precursor. The obtained supramolecular precursor was heated to 500°C in a muffle furnace at a heating rate of 2.3°C / min and maintained at 500°C for 4 hours to obtain tubular g-C3N4, denoted as TCN.

[0048] Step 2, preparation of zinc cobaltate:

[0049] Water and ethylene glycol were mixed in a 1:1 volume ratio to produce an ethylene glycol-water mixed solvent. 0.001 mol Zn(NO₃)₂·6H₂O, 0.002 mol Co(NO₃)₂·6H₂O, and 0.30 g urea were dissolved in 40 mL of the ethylene glycol-water mixed solvent. After stirring for 30 minutes, the resulting mixture was placed in a 100 mL polytetrafluoroethylene-lined stainless steel autoclave and reacted at 120°C for 3 hours. After the reaction, the mixture was cooled to room temperature to obtain a precursor. The precursor was washed three times with water and three times with ethanol, dried, and then heated to 400°C at a heating rate of 5°C / min. It was then calcined in air at 400°C for 2 hours to obtain a black powder, zinc cobalt oxide (ZCO).

[0050] Step 3, preparation of zinc cobaltate heterojunction composite material:

[0051] TCN and zinc cobaltate were placed in a mortar, wherein the amount of zinc cobaltate added accounted for 1% of the total mass of the mixture of TCN and zinc cobaltate; then a small amount of water and ethanol were added as grinding media, and after uniform grinding, the mixture was dried at 60°C for 5 hours to obtain a zinc cobaltate heterojunction composite material, recorded as 1% ZCO / TCN.

[0052] Example 2

[0053] A method for preparing a zinc cobaltate heterojunction composite material comprises the following steps:

[0054] Steps 1 and 2 are carried out according to Example 1.

[0055] Step 3, preparation of zinc cobaltate heterojunction composite material:

[0056] TCN and zinc cobaltate were placed in a mortar, wherein the amount of zinc cobaltate added accounted for 2% of the total mass of the mixture of TCN and zinc cobaltate; then a small amount of water and ethanol were added as grinding media, and after uniform grinding, the mixture was dried at 60°C for 5 hours to obtain a zinc cobaltate heterojunction composite material, recorded as 2% ZCO / TCN.

[0057] Example 3

[0058] A method for preparing a zinc cobaltate heterojunction composite material comprises the following steps:

[0059] Steps 1 and 2 are carried out according to Example 1.

[0060] Step 3, preparation of zinc cobaltate heterojunction composite material:

[0061] TCN and zinc cobaltate were placed in a mortar, wherein the amount of zinc cobaltate added accounted for 4% of the total mass of the mixture of TCN and zinc cobaltate; then a small amount of water and ethanol were added as grinding media, and after uniform grinding, the mixture was dried at 60°C for 5 hours to obtain a zinc cobaltate heterojunction composite material, recorded as 4% ZCO / TCN.

[0062] Example 4

[0063] A method for preparing a zinc cobaltate heterojunction composite material comprises the following steps:

[0064] Steps 1 and 2 are carried out according to Example 1.

[0065] Step 3, preparation of zinc cobaltate heterojunction composite material:

[0066] TCN and zinc cobaltate were placed in a mortar, wherein the added amount of zinc cobaltate accounted for 6% of the total mass of the mixture of TCN and zinc cobaltate; then a small amount of water and ethanol were added as grinding media, and after uniform grinding, the mixture was dried at 60°C for 5 hours to obtain a zinc cobaltate heterojunction composite material, recorded as 6% ZCO / TCN.

[0067] Example 5

[0068] A method for preparing a zinc cobaltate heterojunction composite material comprises the following steps:

[0069] Steps 1 and 2 are carried out according to Example 1.

[0070] Step 3, preparation of zinc cobaltate heterojunction composite material:

[0071] TCN and zinc cobaltate were placed in a mortar, wherein the amount of zinc cobaltate added accounted for 8% of the total mass of the mixture of TCN and zinc cobaltate; then a small amount of water and ethanol were added as grinding media, and after uniform grinding, the mixture was dried at 60°C for 5 hours to obtain a zinc cobaltate heterojunction composite material, recorded as 8% ZCO / TCN.

[0072] Example 6

[0073] A method for preparing a zinc cobaltate heterojunction composite material comprises the following steps:

[0074] Step 1, preparation of bulk g-C3N4:

[0075] 3 g of melamine was placed in a crucible, heated to 500 °C at a heating rate of 2.3 °C / min in a muffle furnace, and kept at 500 °C for 4 h to obtain bulk g-C3N4, which was recorded as BCN.

[0076] Step 2, preparation of zinc cobaltate:

[0077] Water and ethylene glycol were mixed in a 1:1 volume ratio to produce an ethylene glycol-water mixed solvent. 0.001 mol Zn(NO₃)₂·6H₂O, 0.002 mol Co(NO₃)₂·6H₂O, and 0.30 g urea were dissolved in 40 mL of the ethylene glycol-water mixed solvent. After stirring for 30 minutes, the resulting mixture was placed in a 100 mL polytetrafluoroethylene-lined stainless steel autoclave and reacted at 120°C for 3 hours. After the reaction, the mixture was cooled to room temperature to obtain a precursor. The precursor was washed three times with water and three times with ethanol, dried, and then heated to 400°C at a heating rate of 5°C / min. It was then calcined in air at 400°C for 2 hours to obtain a black powder, zinc cobalt oxide (ZCO).

[0078] Step 3, preparation of zinc cobaltate heterojunction composite material:

[0079] BCN and zinc cobaltate were placed in a mortar, wherein the added amount of zinc cobaltate accounted for 1% of the total mass of the mixture of BCN and zinc cobaltate; then a small amount of water and ethanol were added as grinding media, and after uniform grinding, the mixture was dried at 60°C for 5 hours to obtain a zinc cobaltate heterojunction composite material, which was recorded as 1% ZCO / BCN.

[0080] Table 1 Feeding conditions of different addition amounts of zinc cobaltate

[0081] Example Addition amount of zinc cobaltate Zinc cobalt oxide heterojunction composite materials Example 1 1％ 1% ZCO / TCN Example 2 2％ 2% ZCO / TCN Example 3 4％ 4% ZCO / TCN Example 4 6％ 6% ZCO / TCN Example 5 8％ 8% ZCO / TCN

[0082] X-ray diffraction analysis was performed on the zinc cobalt oxide heterojunction composite materials prepared in Examples 1 to 5. The standard card JCPDS: 85-1526 for the tubular g-C3N4, zinc cobalt oxide, and graphite carbon nitride prepared in Example 1 and the standard card JCPDS: 23-1390 for the cubic spinel structure zinc cobalt oxide were used as controls. Figure 1 shown.

[0083] Figure 1 : is the X-ray diffraction pattern of the zinc cobaltate heterojunction composite material prepared in Examples 1 to 5. Figure 1 It can be seen that the tubular g-C3N4 exhibits obvious diffraction peaks at 13.16° and 27.40°, which correspond to the (100) crystal plane and (002) crystal plane of the standard card JCPDS No. 87-152 of graphite phase carbon nitride, respectively. The obvious diffraction peaks of zinc cobalt oxide at 31.2°, 36.8°, 59.3° and 65.1° correspond to the (220) crystal plane, (311) crystal plane, (511) crystal plane and (440) crystal plane of the standard card JCPDS: 23-1390 of cubic spinel structure zinc cobalt oxide, respectively. No impurity signal was detected, which indicates that the tubular graphite phase carbon nitride and ZnCo2O4 samples prepared by the synthesis strategy of Example 1 were successful.

[0084] Figure 2 is the N2 adsorption-desorption isotherm of tubular g-C3N4 and bulk g-C3N4. Figure 2 It can be seen that the specific surface area of ​​tubular g-C3N4 is 10.63m 2 / g, pore diameter of 31.91nm, pore volume of 0.141cm 3 / g. The specific surface area of ​​bulk g-C3N4 is 6.61m 2 / g, pore diameter of 26.58 nm, and pore volume of 0.05 cm 3 / g. Compared to bulk carbon nitride, the specific surface area, pore diameter, and pore volume of tubular carbon nitride are all increased. The rich pore structure and increased specific surface area can improve the adsorption performance of the catalyst and provide more active catalytic sites, which helps increase the mobility of photoexcited carriers, thus predicting that it will achieve good photocatalytic activity.

[0085] Figure 3 is the pore size distribution diagram of tubular g-C3N4 and bulk g-C3N4. Figure 3 It can be seen that compared with bulk g-C3N4, the specific surface area, pore size and pore volume of tubular g-C3N4 are all increased.

[0086] Characteristic peaks of graphite carbon nitride and zinc cobaltate appeared in the X-ray diffraction patterns of the zinc cobaltate heterojunction composite materials prepared in Examples 1 to 5, indicating that the zinc cobaltate heterojunction composite materials of Examples 1 to 5 were successfully synthesized.

[0087] Next, the synergistic hydrogen production performance of the zinc cobaltate heterojunction composite materials prepared in Examples 1 to 5 above as photocatalysts was evaluated.

[0088] Application Example 1

[0089] The zinc cobalt oxide heterojunction composite materials prepared in Examples 1 to 5 are used as photocatalysts for synergistic hydrogen production. The specific application method is as follows:

[0090] Potassium chloroplatinate with a purity of 98% was used as the Pt co-catalyst, and EDTA-2Na was used as the sacrificial agent. The buffer solution was a mixed solution of acetic acid and sodium acetate, with a pH of 5.12. The specific preparation method was: 43.189 mol of acetic acid and 156.811 mol of sodium acetate were mixed to prepare 2 L of the mixed solution.

[0091] 5 mg of photocatalyst was mixed with 5 mL of pH 5.12 buffer solution. 20 μL of 100 mmol / L potassium chloroplatinite solution was added to the reaction system. After mixing, 0.1861 g of EDTA-2Na was added as a sacrificial agent. The reaction was then illuminated under a xenon lamp for 4 hours to allow for photocatalytic synergistic hydrogen production. The mass ratio of photocatalyst, Pt co-catalyst, and sacrificial agent was 5 mg:0.81 mg:0.1861 g.

[0092] The overall reaction process for synergistic hydrogen production is as follows: Under the irradiation of a xenon lamp, the photocatalyst absorbs light energy and generates electron-hole pairs. The electrons and holes separate on the photocatalyst surface, forming a charge-separated state. The separated electrons are then transferred to the surface of the Pt co-catalyst, where they undergo a reduction reaction with water molecules, accelerating the reaction, producing hydrogen. Simultaneously, the holes undergo an oxidation reaction with EDTA-2Na on the photocatalyst surface, generating the corresponding oxidation products. This consumes the holes, preventing recombination between the electrons and holes.

[0093] The synergistic hydrogen production performance under different catalysts was tested, and the results were as follows Figure 4 shown.

[0094] Figure 4 This figure compares the hydrogen production rates of the zinc cobaltate heterojunction composites prepared in Examples 1 to 5, as well as zinc cobaltate, tubular g-C3N4, and bulk g-C3N4 photocatalysts, using EDTA-2Na as the sacrificial agent. ZCO represents zinc cobaltate; BCN represents bulk g-C3N4; and TCN represents tubular g-C3N4.

[0095] Figure 4 The results show that as the amount of zinc cobalt oxide added increases, the hydrogen production rate of the resulting zinc cobalt oxide heterojunction composite material gradually increases. When the amount of zinc cobalt oxide added accounts for 6% of the total mass of the mixture of tubular g-C3N4 and zinc cobalt oxide, the hydrogen production rate of the resulting zinc cobalt oxide heterojunction composite material reaches a maximum of 1193.92 μmol / g / h. With the continued addition of zinc cobalt oxide, the hydrogen production rate of the resulting zinc cobalt oxide heterojunction composite material decreases slightly. Among them, the hydrogen production rate of tubular g-C3N4 is 578.63 μmol / g / h. Compared with a single tubular g-C3N4, the hydrogen production rate of the 6% ZCO / TCN prepared in Example 4 is increased by 2.1 times. The hydrogen production rate of bulk g-C3N4 is 360.75 μmol / g / h. Compared with a single bulk g-C3N4, the hydrogen production rate of the 6% ZCO / TCN prepared in Example 4 is increased by 3.3 times.

[0096] From the perspective of comprehensive hydrogen production rate, the zinc cobaltate heterojunction composite materials prepared in Examples 1 to 5 of the present invention as photocatalysts have relatively higher synergistic hydrogen production performance compared with zinc cobaltate, tubular g-C3N4 and bulk g-C3N4 as catalysts.

[0097] Application Example 2

[0098] The zinc cobalt oxide heterojunction composite material prepared in Example 4 and the tubular g-C3N4 were used as photocatalysts for synergistic hydrogen production. The specific application method is as follows:

[0099] 98% pure potassium chloroplatinate was used as a Pt co-catalyst, and one of seven antibiotics—tetracycline, amoxicillin, ciprofloxacin, gentamicin sulfate, sulfamethazine, oxytetracycline, and cephalexin—was used as a sacrificial agent. The buffer solution was a mixture of acetic acid and sodium acetate, with a pH of 5.12. The specific preparation method was to uniformly mix 43.189 mol of acetic acid and 156.811 mol of sodium acetate to prepare 2 L of the mixed solution.

[0100] 5 mg of photocatalyst was mixed with 5 mL of pH 5.12 buffer solution. 20 μL of 100 mmol / L potassium chloroplatinite solution was added to the reaction system. After mixing, 0.1861 g of antibiotics was added as a sacrificial agent. The reaction was then illuminated under a xenon lamp for 4 hours to allow for photocatalytic synergistic hydrogen production. The mass ratio of photocatalyst, Pt co-catalyst, and sacrificial agent was 5 mg:0.81 mg:0.1861 g.

[0101] The photocatalytic degradation synergistic hydrogen production performance under different antibiotics as sacrificial agents was tested to explore the effect of different antibiotics as sacrificial agents on the synergistic hydrogen production performance. The results are as follows Figure 5 shown.

[0102] Figure 5 This chart compares the hydrogen production rates of the zinc cobaltate heterojunction composite material prepared in Example 4 when different antibiotics are used as sacrificial agents. TC represents tetracycline; AMX represents amoxicillin; CIP represents ciprofloxacin; GNS represents gentamicin sulfate; SMZ represents sulfamethazine; OTC represents oxytetracycline; and CEX represents cephalexin. The 6% ZCO / TCN composite material is the zinc cobaltate heterojunction composite material prepared in Example 4.

[0103] Figure 6 This is a comparison of the hydrogen production rates of tubular g-C3N4 as a photocatalyst when different antibiotics are used as sacrificial agents.

[0104] like Figure 5 and Figure 6As shown in the figure, compared with the tubular g-C3N4, the zinc cobaltate heterojunction composite material prepared in Example 4 has improved hydrogen production effects on seven antibiotics, and the hydrogen production rates are increased by 3.7 times, 1.8 times, 2.6 times, 2.3 times, 2.3 times, 2.1 times and 3.9 times, respectively. The antibiotic with the best hydrogen production effect is GNS, with a hydrogen production rate of 138.16 μmol / g / h.

[0105] In addition, the zinc cobaltate heterojunction composite material and tubular g-C3N4 prepared in Example 4 have degradation effects on seven antibiotics. These results show that the zinc cobaltate heterojunction composite material prepared in the embodiment of the present invention can be used as a bifunctional catalyst, and hydrogen evolution and degradation can be carried out simultaneously.

[0106] From the perspective of comprehensive hydrogen production rate, the performance results of photocatalytic degradation and synergistic hydrogen production using the zinc cobaltate heterojunction composite material prepared in Example 4 as a photocatalyst and different antibiotics as sacrificial agents showed that amoxicillin, ciprofloxacin, gentamicin sulfate or sulfamethazine was used as the sacrificial agent, and the hydrogen production performance was better.

[0107] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A zinc cobaltate heterojunction composite material, characterized in that: The zinc cobaltate heterojunction composite material is prepared by grinding and compounding the tubular graphite phase C3N4 and zinc cobaltate so that the zinc cobaltate is attached to the tubular graphite phase C3N4. The added amount of zinc cobaltate accounts for 1% to 8% of the total mass of the mixture of the tubular graphite phase C3N4 and zinc cobaltate.

2. The zinc cobaltate heterojunction composite material according to claim 1, characterized in that The diameter of the tubular graphite phase C3N4 is 2μm to 3μm; the diameter of the zinc cobaltate is 5μm to 6μm; The added amount of zinc cobaltate accounts for 2% to 8% of the total mass of the mixture of the tubular graphite phase C3N4 and zinc cobaltate.

3. The zinc cobaltate heterojunction composite material according to claim 2, characterized in that The added amount of zinc cobaltate accounts for 6% of the total mass of the mixture of the tubular graphite phase C3N4 and zinc cobaltate.

4. A method for preparing the zinc cobaltate heterojunction composite material according to any one of claims 1 to 3, characterized in that: The following steps are involved: The tubular graphite phase C3N4 and zinc cobaltate are ground and composited so that the zinc cobaltate is attached to the tubular graphite phase C3N4 to obtain a zinc cobaltate heterojunction composite material.

5. The method for preparing the zinc cobaltate heterojunction composite material according to claim 4, wherein: The grinding and compounding is carried out by wet grinding, and the medium of wet grinding is water and ethanol.

6. The method for preparing the zinc cobaltate heterojunction composite material according to claim 4, wherein: The tubular graphite phase C3N4 is prepared by the following method: After mixing melamine, an acid catalyst and water, a hydrothermal reaction is carried out at 170°C to 190°C to cause a polycondensation reaction between melamine molecules to form a supramolecular precursor; The supramolecular precursor is calcined at 450° C. to 600° C. to cause thermal decomposition and reconstruction of the supramolecular precursor to form a tubular graphite phase C3N4.

7. The method for preparing the zinc cobaltate heterojunction composite material according to claim 6, characterized in that: The acid catalyst is phosphoric acid.

8. The method for preparing the zinc cobaltate heterojunction composite material according to claim 6, characterized in that: The mass ratio of melamine to acid catalyst is 3:1-3; The usage ratio of melamine and water is 3g:70mL~100mL.

9. Use of the zinc cobaltate heterojunction composite material according to any one of claims 1 to 3 as a photocatalyst for synergistic hydrogen production.

10. The use of the zinc cobaltate heterojunction composite material according to claim 9 as a photocatalyst for synergistic hydrogen production, characterized in that: The specific application method is: The photocatalyst, Pt co-catalyst and sacrificial agent are mixed evenly in a buffer solution system, and then photocatalytic synergistic hydrogen production is carried out under light conditions; The mass ratio of the photocatalyst, Pt co-catalyst and sacrificial agent is 5 mg: 0.5 mg to 1 mg: 0.1 g to 0.2 g; The ratio of photocatalyst to buffer solution is 1 mg: 1 mL to 5 mL; The Pt co-catalyst is potassium chloroplatinite; The sacrificial agent is any one of EDTA-2Na, tetracycline, amoxicillin, ciprofloxacin, gentamicin sulfate, sulfamethazine, oxytetracycline and cephalexin; The buffer solution is a mixed solution of acetic acid and sodium acetate, with a pH of 5-6.

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