Biphase nickel sulfide, preparation method and application thereof, and catalyst composition

Abstract

The invention provides biphase nickel sulfide, a preparation method and application thereof and a catalyst composition, and belongs to the technical field of catalyst auxiliaries. According to the preparation method of the double-phase nickel sulfide, under the condition that the pH value is 12-14, Ni < 2 + > in a soluble nickel source and OH <-> in a system firstly generate nickel hydroxide precipitation particles, then NiS is gradually generated along with the rise of the reaction temperature in the hydrothermal process, C2H5NS is hydrolyzed to generate S < 2-> under the alkaline condition, the progress of the vulcanization reaction is accelerated, and the reaction time is shortened. Therefore, metastable-state alpha-NiS is preferentially generated in the initial stage of the reaction, beta-NiS is gradually generated along with the prolonging of the reaction time, and thus the double-phase nickel sulfide material is obtained. The two crystal structures can effectively promote decomposition of H2O into H < + > and OH <->, and the photocatalytic hydrogen production rate is increased.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of catalyst additives, and particularly relates to a dual-phase nickel sulfide as well as a preparation method and application thereof and a catalyst composition. BACKGROUND

[0002] Photocatalytic hydrogen production is one of the important ways to realize the transformation to green energy, and developing efficient hydrogen production catalyst additives is an effective way to improve the efficiency of photocatalytic hydrogen production. In the prior art, although the performance can be improved by introducing noble metals (such as platinum) as a catalyst additive, the noble metals are high in cost and scarce in resources. Transition metal sulfides are widely studied in the field of photocatalysis due to their small band gap structure, high electrical conductivity, low cost and high catalytic activity. Among them, NiS material has two common crystal structures, namely hexagonal α-NiS and cubic β-NiS. Both of the two crystal structures have been proved to be able to effectively promote the decomposition of H2O into H2 and OH-, and exhibit excellent photocatalytic hydrogen production performance. For example, one prior art synthesized α-NiS and β-NiS additives by a solvothermal method and loaded them on CdS, respectively, and achieved the optimal hydrogen production rates of 5501.9 μmol g-1 h-1 and 3793.1 μmol g-1 h-1, respectively. However, the preparation of the two different crystal structures of NiS by one-step method and the synergistic catalysis of the dual crystal structure are still in a blank state. + and OH- - - 1 h -1 and 3793.1 μmol g-1 h-1 -1 h -1 SUMMARY

[0003] The purpose of the present application is to provide a dual-phase nickel sulfide as well as a preparation method and application thereof and a catalyst composition. The dual-phase nickel sulfide is prepared by one-step method, and when applied to photocatalytic water splitting for hydrogen production, has a more optimal hydrogen production rate than the single crystal structure.

[0004] In order to achieve the purpose of the present application, the present application provides the following technical solutions:

[0005] A preparation method of a dual-phase nickel sulfide, comprising the following steps:

[0006] subjecting a sulfur-containing nickel aqueous solution to a hydrothermal reaction to obtain the dual-phase nickel sulfide; the chemical composition of the dual-phase nickel sulfide comprises α-NiS and β-NiS;

[0007] The solute in the sulfur-containing nickel aqueous solution comprises a soluble nickel salt and a soluble sulfur source, and the pH value is 12-14;

[0008] ​​The soluble sulfur source is C2H5NS; and the molar ratio of the nickel element in the soluble nickel salt to the sulfur element in the soluble sulfur source is 1:1-4.

[0009] Preferably, the soluble nickel salt is one or more of hydrochloride, nitrate and acetate of nickel.

[0010] Preferably, the reagent used for adjusting the pH value of the aqueous nickel-sulfur solution is a strong base.

[0011] Preferably, the temperature of the hydrothermal reaction is 160-200 ℃, and the time is 12-24 h.

[0012] Preferably, the heating rate for heating to the temperature required for the hydrothermal reaction is 5-10 ℃ / min.

[0013] The application further provides the dual-phase nickel sulfide obtained by the preparation method.

[0014] Preferably, the particle size of the dual-phase nickel sulfide is 10-50 nm.

[0015] The application further provides the application of the dual-phase nickel sulfide in photocatalytic decomposition of water to produce hydrogen.

[0016] The application further provides a catalyst composition, which comprises a photocatalyst and a catalytic aid loaded on the photocatalyst.

[0017] The photocatalyst comprises one or more of g-C3N4, TiO2, CdS and CdZnS.

[0018] The catalytic aid is the dual-phase nickel sulfide.

[0019] Preferably, the content of the dual-phase nickel sulfide in the catalyst composition is 10-25 wt%.

[0020] The application provides a preparation method of dual-phase nickel sulfide, which comprises the following steps: subjecting an aqueous nickel-sulfur solution to hydrothermal reaction to obtain the dual-phase nickel sulfide; the chemical composition of the dual-phase nickel sulfide comprises α-NiS and β-NiS; the solute in the aqueous nickel-sulfur solution comprises a soluble nickel salt and a soluble sulfur source, and the pH value is 12-14; the soluble sulfur source is C2H5NS; and the molar ratio of the nickel element in the soluble nickel salt to the sulfur element in the soluble sulfur source is 1:1-4. 2+ First, it will react with OH -The nickel hydroxide precipitation particles are generated, and then gradually generate NiS in a hydrothermal process as the reaction temperature increases, and C2H5NS hydrolysis generates S under alkaline conditions 2- , thereby generating metastable α-NiS preferentially in the initial stage of the reaction, and gradually generating β-NiS as the reaction time is prolonged, so that a dual-phase nickel sulfide material is obtained. In the present application, α-NiS and β-NiS are closely combined, have the advantages of small size and rapid electron transfer, and both crystal structures can effectively promote H2O to be decomposed into H + and OH - , thereby improving the photocatalytic hydrogen production rate; and the preparation method provided by the present application has the advantages of simple process, mild conditions and low cost. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0022] Figure 1 Mechanism diagram of the catalyst composition for photocatalytic decomposition of water to produce hydrogen according to the present application;

[0023] Figure 2 XRD pattern of the nickel sulfide obtained in Example 1 and Comparative Examples 1-3;

[0024] Figure 3 TEM pattern of the dual-phase nickel sulfide material obtained in Example 1;

[0025] Figure 4 XRD pattern of the catalyst composition for photocatalytic decomposition of water to produce hydrogen obtained in Application Example 3 and Comparative Application Example 1;

[0026] Figure 5 TEM and HRTEM patterns of the catalyst composition for photocatalytic decomposition of water to produce hydrogen obtained in Application Example 3; wherein (a) is a TEM pattern, and (b) is an HRTEM pattern;

[0027] Figure 6 Hydrogen production rate diagram of the catalyst composition for photocatalytic decomposition of water to produce hydrogen obtained in Application Examples 1-4 and Comparative Application Examples 1-4. DETAILED DESCRIPTION

[0028] The present application provides a preparation method of dual-phase nickel sulfide, comprising the following steps:

[0029] The sulfur-containing nickel aqueous solution is subjected to a hydrothermal reaction to obtain the dual-phase nickel sulfide; the chemical composition of the dual-phase nickel sulfide comprises α-NiS and β-NiS;

[0030] The solute in the aqueous solution containing nickel and sulfur includes a soluble nickel salt and a soluble sulfur source, and the pH value is 12-14;

[0031] The soluble sulfur source is C2H5NS; the molar ratio of the nickel element in the soluble nickel salt to the sulfur element in the soluble sulfur source is 1:1-4.

[0032] In the present application, all the raw materials for preparation are commercially available products well known to those skilled in the art, unless otherwise specified.

[0033] In the present application, the soluble nickel salt is one or more of the hydrochloride, nitrate or acetate of nickel, and in specific embodiments, can be nickel chloride, nickel nitrate or nickel acetate. In the present application, the soluble nickel source is not limited as to whether it contains crystal water.

[0034] In the present application, the soluble sulfur source is C2H5NS. By adjusting the pH value to 12-14, the release rate of S 2- from C2H5NS can be controlled, and the concentration of the reactants can be precisely controlled, so that the product contains both alpha-NiS and beta-NiS crystal structures, and S 2- is released more gently from C2H5NS than from other soluble sulfur sources such as thiourea, and S 2- is released more rapidly from Na2S. Different sulfur sources and reactant concentrations will affect the generation of the product, and the generated nickel sulfide phases, including NiS, Ni3S4, NiS2, etc., will gradually tend to generate NiS2 with increasing sulfur-nickel ratio in the feed; or with the same sulfur-nickel ratio, the reactant concentration is doubled in the same proportion, and the nickel sulfide will gradually tend to generate Ni3S4.

[0035] In the present application, the molar ratio of the nickel element in the soluble nickel salt to the sulfur element in the soluble sulfur source is 1:1-4, and in specific embodiments, can be 1:1.5, 1:2 or 1:3.

[0036] In the present application, the water in the aqueous solution containing nickel and sulfur can be deionized water. In the present application, the molar amount of the nickel element in the soluble nickel salt to the volume of water is 1 mol:60-80 L; and the molar amount of the sulfur element in the soluble sulfur source to the volume of water is 1.5 mol:60-80 L.

[0037] The present application does not have special limitations on the mixing method of the soluble nickel salt, the soluble sulfur source and water, and the soluble nickel source, the soluble sulfur source and water can be mixed uniformly.

[0038] In the present application, the reagent for adjusting the pH value of the aqueous solution containing sulfur and nickel is a strong base; in specific embodiments, it can be NaOH or KOH; the sodium hydroxide is used in the form of an aqueous solution of sodium hydroxide; the present application does not have a special limitation on the concentration of the aqueous solution of NaOH, and in specific embodiments, the concentration can be 1-10 mol / L. In the present application, the pH value is adjusted to 12-14, and in specific embodiments, it can be 12.5 or 13.5.

[0039] In the present application, the temperature of the hydrothermal reaction is 160-200℃, and in specific embodiments, it can be 180℃; the time is 12-24h, and in specific embodiments, it can be 16 or 20h; the heating rate required to heat to the temperature of the hydrothermal reaction is 5-10℃ / min. In the present application, the equipment for the hydrothermal reaction is a hydrothermal synthesis reaction kettle configured with an inner lining. In the present specific embodiment, the material of the inner lining in the hydrothermal synthesis reaction kettle can be polytetrafluoroethylene.

[0040] In the present application, the reaction occurring during the hydrothermal reaction process is shown in formula 1-formula 4:

[0041] Ni 2+ +2OH - →Ni(OH)2 formula 1;

[0042] C2H5NS+2OH - →CH3COO-+NH3+S 2- +H2O formula 2;

[0043] Ni(OH)2+S 2- →NiS+2OH - formula 3;

[0044] In the present application, under the condition of pH 12-14, Ni 2+ will first react with OH - to generate light green precipitated particles, and then in the hydrothermal process, with the increase of the reaction temperature, NiS is gradually generated, C2H5NS hydrolyzes to generate S 2- under alkaline conditions at about 60-80℃, which accelerates the progress of the vulcanization reaction, so that the metastable α-NiS is preferentially generated in the initial stage of the reaction, and β-NiS is gradually generated with the extension of the reaction time, obtaining a dual-phase nickel sulfide material.

[0045] In the present application, the product obtained by the hydrothermal reaction is sequentially washed and dried; the washing is water washing and centrifugation. The present application does not have a special limitation on the water washing and centrifugation, and water washing and centrifugation known to those skilled in the art can be used. In the present application, the temperature of the drying is 60-70℃, and in specific embodiments, it can be 60 or 68℃; the time is 6-12h, and in specific embodiments, it can be 7-10h.

[0046] In the present application, the nickel sulfide material is gray-black.

[0047] The present application also provides the dual-phase nickel sulfide obtained by the preparation method of the above technical solution, and the chemical composition of the dual-phase nickel sulfide comprises α-NiS and β-NiS.

[0048] In the present application, the particle size of the dual-phase nickel sulfide is 10-50 nm, and in specific embodiments, it can be 22, 28, 30, 36 or 44 nm.

[0049] The present application also provides the application of the dual-phase nickel sulfide of the above technical solution in photocatalytic decomposition of water to produce hydrogen.

[0050] The present application also provides a catalyst composition comprising a photocatalyst and a catalytic aid; the photocatalyst comprises one or more of g-C3N4, TiO2, CdS and CdZnS;

[0051] The catalytic aid is the dual-phase nickel sulfide of the above technical solution.

[0052] In specific embodiments of the present application, the g-C3N4 can be g-C3N4 nanosheets; the preparation method of the g-C3N4 nanosheets comprises the following steps:

[0053] The carbon-nitrogen compound is subjected to a thermal polymerization reaction to obtain g-C3N4 particles;

[0054] The g-C3N4 particles are sequentially subjected to ultrasonic dispersion and drying to obtain the g-C3N4 nanosheets.

[0055] In the present application, the carbon-nitrogen compound is one or more of urea, cyanamide, dicyandiamide, melamine and thiourea.

[0056] In the present application, the thermal polymerization reaction is that the carbon-nitrogen compound is placed in a crucible, wrapped with tin paper, and then the wrapped system is placed in a microwave muffle furnace, heated to the thermal polymerization reaction temperature in air and kept for a certain time. In the present application, the temperature of the thermal polymerization reaction is 500-600℃, and in specific embodiments, it can be 520 or 580℃; the time is 2-4 h, and in specific embodiments, it can be 2.5 or 3.5 h. In the present application, the heating rate to the thermal polymerization reaction is 3-10℃ / min, and in specific embodiments, it can be 4 or 7℃ / min.

[0057] After the thermal polymerization reaction, the product obtained by the thermal polymerization reaction is ground to obtain g-C3N4 particles. The present application does not have special limitations on the grinding, and powder-like g-C3N4 particles can be obtained.

[0058] After obtaining the g-C3N4 particles, the g-C3N4 particles are sequentially subjected to ultrasonic dispersion and drying to obtain the g-C3N4 nanosheets.

[0059] In the present application, the g-C3N4 particles are dispersed in water and subjected to ultrasonic dispersion. In the present application, the water is deionized water. The present application does not have a special limitation on the frequency of the ultrasonic dispersion, and a frequency of ultrasonic familiar to those skilled in the art can be used. In the present application, the time of the ultrasonic dispersion can be 10 h.

[0060] In the present application, the temperature of the drying is 50-70°C; the present application does not have a special limitation on the time of the drying, and the time can be determined according to the removal of the water attached to the g-C3N4 nanosheets.

[0061] In the present application, the content of the dual-phase nickel sulfide in the photocatalytic water-splitting hydrogen production catalyst composition is 10-25 wt%, and in specific embodiments, can be 15 or 20 wt%.

[0062] In the present application, the dual-phase nickel sulfide and the photocatalyst are mixed, and the obtained catalyst composition is subjected to photocatalytic water-splitting hydrogen production.

[0063] In the present application, the mixing of the dual-phase nickel sulfide and the photocatalyst comprises the following steps: mixing the dispersion suspension of the dual-phase nickel sulfide and the dispersion suspension of the photocatalyst, and stirring and evaporating to remove the dispersion solvent in the dispersion suspension of the dual-phase nickel sulfide and the dispersion suspension of the photocatalyst to obtain the photocatalytic water-splitting hydrogen production catalyst composition.

[0064] In the present application, the dual-phase nickel sulfide and the dispersion solvent are mixed to obtain the dispersion suspension of the dual-phase nickel sulfide. The present application does not have a special limitation on the type of the dispersant, and in specific embodiments, can be ethanol or water. In the present application, the ratio of the mass of the dual-phase nickel sulfide to the volume of the dispersion solvent is 3-20 g:10 L. In the present application, the mixing of the dual-phase nickel sulfide and the dispersion solvent can be ultrasonic mixing.

[0065] In the present application, the photocatalyst and the dispersion solvent are mixed to obtain the dispersion suspension of the photocatalyst. The present application does not have a special limitation on the type of the dispersant, and in specific embodiments, can be ethanol or water. In the present application, the ratio of the mass of the photocatalyst to the volume of the dispersion solvent is 100 g:10 L. In the present application, the mixing of the photocatalyst and the dispersion solvent can be ultrasonic mixing.

[0066] In the present application, the stirring rate is 400-500 rpm, and in specific embodiments, can be 440 or 460 rpm.

[0067] In the present application, the photocatalytic water-splitting hydrogen production catalyst composition is blue-gray.

[0068] In the present application, the photocatalyst and the catalytic aid are mixed by solvent mixing physical compounding method, the obtained catalyst composition has no loss, the composition of the composition is consistent with the original charge, and the operation is relatively simple; compared with the in-situ deposition or growth of the photocatalyst and the catalytic aid used in the prior art, the composition composition of the present application is more easily controlled.

[0069] The present application is not particularly limited to the photocatalytic decomposition of water to produce hydrogen, and the photocatalytic decomposition of water to produce hydrogen known to those skilled in the art can be used.

[0070] In the present application, the mechanism diagram of the photocatalytic decomposition of water to produce hydrogen of the catalyst composition is as shown in Figure 1 Under light irradiation, the photocatalyst (g-C3N4) absorbs light energy to generate photo-generated electrons and holes, the electrons jump to the conduction band (CB) of the photocatalyst (g-C3N4), and the holes remain in the valence band (VB); due to the existence of the Schottky barrier, the electrons can be transferred to the nickel sulfide aid in a "one-way" irreversible manner, thereby rapidly reducing H + to H2, while the holes on the VB oxidize triethanolamine (TEOA), realizing photocatalytic decomposition of water to produce hydrogen.

[0071] In order to further illustrate the present application, the dual-phase nickel sulfide provided by the present application, the preparation method and application thereof, and the catalyst composition are described in detail below in conjunction with the drawings and examples, but they cannot be understood as limiting the scope of protection of the present application.

[0072] Example 1

[0073] 1 mmol of Ni(CH3COO)2·4H2O, 1.5 mmol of C2H5NS and 60 mL of deionized water were mixed, NaOH was added to adjust the pH value to 13, and magnetic stirring was performed for 30 min until the mixture was uniform, then it was transferred and sealed in a hydrothermal synthesis reaction tank with a polytetrafluoroethylene liner, heated from room temperature to 180℃ at a heating rate of 5℃ / min, and hydrothermal reaction was carried out at 180℃ for 18 h, the obtained hydrothermal reaction product was cooled, washed with water and centrifuged for 3 times, and then dried at 60℃ for 10 h to obtain gray-black dual-phase nickel sulfide particles α / β-NiS.

[0074] Comparative Example 1

[0075] 1 mmol of Ni(CH3COO)2·4H2O, 1.5 mmol of C2H5NS and 5 mmol of urea were mixed in 60 mL of deionized water and stirred for 30 min, then transferred and sealed in a hydrothermal synthesis reaction tank with a polytetrafluoroethylene liner, and hydrothermal reaction was carried out at 180℃ for 18 h, the obtained hydrothermal reaction product was cooled, washed with water and centrifuged for 3 times, and then dried at 60℃ for 10 h to obtain single-phase nickel sulfide particles α-NiS.

[0076] Comparative Example 2

[0077] 1 mmol of Ni(CH3COO)2·4H2O, 5 mmol of thiourea, and 60 mL of deionized water were mixed. NaOH was added to adjust the pH to 13. The mixture was magnetically stirred for 30 min to achieve uniform mixing. The mixture was then transferred and sealed in a hydrothermal synthesis reactor with a polytetrafluoroethylene liner. The hydrothermal reaction was carried out at 180 °C for 18 h. The resulting hydrothermal reaction product was cooled, washed with water, centrifuged three times, and dried at 60 °C for 10 h to obtain single-phase nickel sulfide particles β-NiS.

[0078] Comparative Example 3

[0079] 1 mmol of Ni(CH3COO)2·4H2O, 1.5 mmol of C2H5NS and 60 mL of deionized water were mixed and magnetically stirred for 30 min to achieve uniform mixing. The mixture was then transferred and sealed in a hydrothermal synthesis reactor with a polytetrafluoroethylene liner. The mixture was hydrothermally reacted at 180 °C for 18 h. The resulting hydrothermal reaction product was cooled, washed with water and centrifuged three times, and then dried at 60 °C for 10 h to obtain NiS-Ni3S4 material.

[0080] Performance Characterization

[0081] X-ray diffraction tests were performed on the nickel sulfide materials obtained in Example 1 and Comparative Examples 1-3, and the obtained XRD patterns are shown below. Figure 2 As shown.

[0082] Depend on Figure 2 It can be seen that the XRD pattern of the biphase nickel sulfide (α / β-NiS) prepared in Example 1 corresponds to the two standard cards (JCPDS PDF#02-1280, JCPDS PDF#12-0041) of α-NiS and β-NiS. The peaks appearing near 46.0° and 53.5° correspond to the (102) and (110) crystal planes of α-NiS, and the diffraction peaks appearing at 18.4°, 30.3°, 32.3°, 35.6°, 37.3°, 40.5° and 48.8° correspond to the (110), (101), (300), (021), (220), (211) and (131) crystal planes of β-NiS, respectively. The NiS-Ni3S4 composite material obtained in Comparative Example 3 showed characteristic diffraction peaks belonging to Ni3S4 (JCPDS PDF#47-1739) at positions of 26.6°, 31.3°, 37.9°, 50.0° and 54.7°.

[0083] The biphase nickel sulfide material obtained in Example 1 was subjected to diffraction electron microscopy (SEM) analysis, and the resulting SEM images are shown below. Figure 3 As shown, by Figure 3 It can be seen that α / β-NiS is composed of uniform particles with a particle size of approximately 10–50 nm.

[0084] Application Example 1

[0085] A photocatalyst suspension was prepared by ultrasonic mixing 90 mg of g-C3N4 nanosheets with 10 mL of ethanol for 2 h. A nickel sulfide suspension was prepared by ultrasonic mixing 10 mg of the α / β-NiS particles obtained in Example 1 with 10 mL of ethanol for 2 h. The two suspensions were mixed and the ethanol was removed by evaporation under continuous stirring to obtain a blue-gray powder of the photocatalytic water-splitting hydrogen production catalyst composition, denoted as 10% α / β-NiS / g-C3N4.

[0086] Application Example 2

[0087] A photocatalytic water-splitting hydrogen production catalyst composition was prepared according to the method described in Application Example 1, except that the mass of g-C3N4 nanosheets was 85 mg and the mass of α / β-NiS particles was 15 mg, denoted as 15% α / β-NiS / g-C3N4.

[0088] Application Example 3

[0089] A photocatalytic water-splitting hydrogen production catalyst composition was prepared according to the method described in Application Example 1, except that the mass of g-C3N4 nanosheets was 80 mg and the mass of α / β-NiS particles was 20 mg, denoted as 20% α / β-NiS / g-C3N4.

[0090] Application Example 4

[0091] A photocatalytic water-splitting hydrogen production catalyst composition was prepared according to the method described in Application Example 1, except that the mass of g-C3N4 nanosheets was 75 mg and the mass of α / β-NiS particles was 25 mg, denoted as 25% α / β-NiS / g-C3N4.

[0092] Comparative Application Example 1

[0093] g-C3N4 nanosheets.

[0094] Comparative Application Example 2

[0095] A photocatalytic water-splitting hydrogen production catalyst composition was prepared according to the method described in Application Example 3, except that the mass of g-C3N4 nanosheets was 80 mg and the mass of α-NiS nanoparticles obtained in Comparative Example 1 was 20 mg, denoted as 20% α-NiS / g-C3N4.

[0096] Comparative Application Example 3

[0097] The catalyst composition for photocatalytic splitting water to produce hydrogen was prepared according to the method described in Application Example 3, except that the mass of g-C3N4 nanosheets was 80 mg, and the mass of β-NiS nanoparticles obtained in Comparative Example 2 was 20 mg, denoted as 20% β-NiS / g-C3N4.

[0098] Comparative Application Example 4

[0099] The catalyst composition for photocatalytic splitting water to produce hydrogen was prepared according to the method described in Application Example 3, except that the mass of g-C3N4 nanosheets was 80 mg, and the mass of NiS-Ni3S4 nanoparticles obtained in Comparative Example 3 was 20 mg, denoted as 20% NiS-Ni3S4 / g-C3N4.

[0100] Comparative Application Example 5

[0101] The catalyst composition for photocatalytic splitting water to produce hydrogen was prepared according to the method described in Application Example 1, and the catalytic additive was 5 mg of α-NiS and 5 mg of β-NiS. The hydrogen rate of the obtained catalyst composition was measured to be 602.0 μmol g -1 h -1 . Since α-NiS and β-NiS were independently synthesized and then compounded by physical methods, no effective synergistic effect was formed between them. Therefore, the actual hydrogen production rate was lower than when β-NiS was loaded alone, but still better than when α-NiS was loaded alone.

[0102] Performance characterization

[0103] The catalyst composition for photocatalytic splitting water to produce hydrogen obtained in Application Example 3 and Comparative Application Example 1 was subjected to X-ray diffraction test, and the obtained XRD pattern is shown in Figure 4 .

[0104] As can be seen from Figure 4 , the XRD pattern of pure g-C3N4 nanosheets, 27.4° and 13.0° correspond to the (100) and (002) crystal planes of g-C3N4, respectively; the main diffraction peak of g-C3N4 is well preserved after loading α / β-NiS, indicating that g-C3N4 was not destroyed during the evaporation process of the solvent (ethanol).

[0105] The catalyst composition for photocatalytic splitting water to produce hydrogen obtained in Application Example 3 was subjected to transmission electron microscopy test, and the obtained TEM and HRTEM images are shown in Figure 5 . Figure 5 , (a) is a TEM image, and (b) is an HRTEM image. As can be seen from Figure 5 , the α / β-NiS nanoparticles in the catalyst composition for photocatalytic splitting water to produce hydrogen were successfully loaded onto the surface of g-C3N4, and the lattice fringes of 0.486 nm and 0.237 nm correspond to the (110) plane and (220) plane of β-NiS, respectively.

[0106] The photocatalytic water-splitting hydrogen production catalyst compositions obtained in application examples 1-4 and comparative application examples 1-4 were subjected to catalytic hydrogen production tests.

[0107] The specific test method was as follows: the test was performed in a Labsolar-III AG type photocatalytic water-splitting hydrogen production device, the light source was a 300 W xenon lamp (CEL-HXF300), the illumination area was 24 cm 2 , and the light intensity was measured by a light radiometer (PL-MW2000) before hydrogen production;

[0108] The specific operation was as follows: first, a 20 vol% sacrificial agent mixture (80 mL of deionized water and 20 mL of triethanolamine) was prepared; then, 10 mg of the sample to be tested was dispersed in the sacrificial agent, and the obtained suspension was placed in the reactor for magnetic stirring; after the device was assembled, the interior of the device and the sacrificial agent mixture were vacuumed to remove air; finally, the light was turned on to perform the hydrogen production experiment, and the hydrogen production rate was measured every 1 h; the obtained hydrogen production rate graph is shown in Figure 6 .

[0109] As can be seen from Figure 6 , the photocatalytic water-splitting hydrogen production catalyst composition (20w% α / β-NiS / g-C3N4) provided in application example 3 had the highest hydrogen production rate, which was 24634.04 μmol·g -1 ·h -1 , which was 209.4 times higher than that of the g-C3N4 nanosheet provided in comparative application example 1 (117.08 μmol·g -1 ·h -1 ); and the hydrogen production rate of the photocatalytic water-splitting hydrogen production catalyst composition (20w% α / β-NiS / g-C3N4) provided in application example 3 was 48.25 times and 20.11 times higher than those of 20% α-NiS / g-C3N4 in comparative application example 2 and 20% β-NiS / g-C3N4 in comparative application example 3, respectively, indicating that the dual-phase nickel sulfide material (α / β-NiS particles) prepared in the application had better catalytic performance as a catalyst additive for photocatalytic hydrogen evolution reaction than α-NiS or β-NiS alone.

[0110] Although the above embodiments have made a detailed description of the present application, it is only a part of the embodiments of the present application, not all the embodiments, and other embodiments can be obtained according to the present embodiments without creativity, which all belong to the protection scope of the present application.

Claims

1. A method for producing a two-phase nickel sulfide, characterized by, The method comprises the following steps: The biphase nickel sulfide is obtained by hydrothermal reaction of a nickel sulfide-containing aqueous solution; the chemical composition of the biphase nickel sulfide comprises α-NiS and β-NiS; The solute in the nickel sulfide-containing aqueous solution comprises a soluble nickel salt and a soluble sulfur source, and the pH value is 12-14; The soluble sulfur source is C2H5NS; the molar ratio of nickel element in the soluble nickel salt to sulfur element in the soluble sulfur source is 1:1-4.

2. The production method according to claim 1, characterized by, The soluble nickel salt is one or more of hydrochloride, nitrate and acetate of nickel.

3. The production method according to claim 1, characterized by, The reagent for adjusting the pH value of the nickel sulfide-containing aqueous solution is a strong base.

4. The method of claim 1, wherein, The temperature of the hydrothermal reaction is 160-200 ℃, and the time is 12-24 h.

5. The preparation method according to claim 4, characterized in that, The temperature rising rate for rising to the temperature required by the hydrothermal reaction is 5-10 ℃ / min.

6. The double-phase nickel sulfide obtained by the production method according to any one of claims 1 to 5, characterized in that, The chemical composition of the biphase nickel sulfide comprises α-NiS and β-NiS.

7. The nickel sulfide of claim 6, wherein, The particle size of the biphase nickel sulfide is 10-50 nm.

8. Application of the biphase nickel sulfide of claim 6 or 7 to photocatalytic decomposition of water to produce hydrogen.

9. A catalyst composition characterized in that, The photocatalyst comprises one or more of g-C3N4, TiO2, CdS and CdZnS; The catalytic aid is the biphase nickel sulfide of claim 6 or 7. The content of the biphase nickel sulfide in the catalyst composition is 10-25 wt%.

10. The catalyst composition of claim 9, wherein ​

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