CN113042091A - Simple and efficient g-C lifting device3N4Method for preparing hydrogen activity by photocatalysis - Google Patents
Simple and efficient g-C lifting device3N4Method for preparing hydrogen activity by photocatalysis Download PDFInfo
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- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 title claims abstract description 38
- 229910052739 hydrogen Inorganic materials 0.000 title claims abstract description 38
- 239000001257 hydrogen Substances 0.000 title claims abstract description 38
- 230000001699 photocatalysis Effects 0.000 title claims abstract description 36
- 230000000694 effects Effects 0.000 title claims abstract description 21
- 238000007146 photocatalysis Methods 0.000 title claims description 13
- 238000004519 manufacturing process Methods 0.000 claims abstract description 26
- 238000000034 method Methods 0.000 claims abstract description 23
- 239000011941 photocatalyst Substances 0.000 claims abstract description 11
- 229910052784 alkaline earth metal Inorganic materials 0.000 claims abstract description 9
- 150000001342 alkaline earth metals Chemical class 0.000 claims abstract description 8
- 229910052783 alkali metal Inorganic materials 0.000 claims abstract description 7
- 150000001340 alkali metals Chemical class 0.000 claims abstract description 7
- 238000000926 separation method Methods 0.000 claims abstract description 5
- 229910052751 metal Inorganic materials 0.000 claims abstract description 4
- 239000002184 metal Substances 0.000 claims abstract description 4
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 73
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 13
- ZGTMUACCHSMWAC-UHFFFAOYSA-L EDTA disodium salt (anhydrous) Chemical compound [Na+].[Na+].OC(=O)CN(CC([O-])=O)CCN(CC(O)=O)CC([O-])=O ZGTMUACCHSMWAC-UHFFFAOYSA-L 0.000 claims description 8
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 claims description 8
- 238000001816 cooling Methods 0.000 claims description 8
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 claims description 6
- 239000000725 suspension Substances 0.000 claims description 5
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 claims description 4
- 239000004202 carbamide Substances 0.000 claims description 4
- 238000012360 testing method Methods 0.000 claims description 4
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 3
- 238000006243 chemical reaction Methods 0.000 claims description 3
- 239000003153 chemical reaction reagent Substances 0.000 claims description 3
- 238000002360 preparation method Methods 0.000 claims description 3
- 238000010438 heat treatment Methods 0.000 claims description 2
- 230000006378 damage Effects 0.000 claims 1
- 238000003780 insertion Methods 0.000 claims 1
- 230000037431 insertion Effects 0.000 claims 1
- 150000002500 ions Chemical class 0.000 abstract description 6
- 230000005595 deprotonation Effects 0.000 abstract description 2
- 238000010537 deprotonation reaction Methods 0.000 abstract description 2
- 239000003814 drug Substances 0.000 abstract description 2
- 230000001105 regulatory effect Effects 0.000 abstract description 2
- 238000003860 storage Methods 0.000 abstract description 2
- 239000011734 sodium Substances 0.000 description 8
- 230000003197 catalytic effect Effects 0.000 description 7
- 239000003054 catalyst Substances 0.000 description 6
- JMANVNJQNLATNU-UHFFFAOYSA-N oxalonitrile Chemical compound N#CC#N JMANVNJQNLATNU-UHFFFAOYSA-N 0.000 description 6
- 238000002474 experimental method Methods 0.000 description 5
- 238000012546 transfer Methods 0.000 description 5
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 4
- 239000011148 porous material Substances 0.000 description 4
- 229910052708 sodium Inorganic materials 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 3
- 238000003917 TEM image Methods 0.000 description 3
- 230000001351 cycling effect Effects 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
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- 238000001878 scanning electron micrograph Methods 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 239000001569 carbon dioxide Substances 0.000 description 2
- 229910002092 carbon dioxide Inorganic materials 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 230000003750 conditioning effect Effects 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 230000031700 light absorption Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
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- 239000002243 precursor Substances 0.000 description 2
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- 238000011160 research Methods 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- UMGDCJDMYOKAJW-UHFFFAOYSA-N thiourea Chemical compound NC(N)=S UMGDCJDMYOKAJW-UHFFFAOYSA-N 0.000 description 2
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 1
- 229920000877 Melamine resin Polymers 0.000 description 1
- 239000007832 Na2SO4 Substances 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 150000008044 alkali metal hydroxides Chemical class 0.000 description 1
- 229910001860 alkaline earth metal hydroxide Inorganic materials 0.000 description 1
- QGZKDVFQNNGYKY-UHFFFAOYSA-N ammonia Natural products N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 229910052796 boron Inorganic materials 0.000 description 1
- 238000001354 calcination Methods 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
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- 238000006731 degradation reaction Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- QGBSISYHAICWAH-UHFFFAOYSA-N dicyandiamide Chemical compound NC(N)=NC#N QGBSISYHAICWAH-UHFFFAOYSA-N 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 229910052731 fluorine Inorganic materials 0.000 description 1
- LELOWRISYMNNSU-UHFFFAOYSA-N hydrogen cyanide Chemical compound N#C LELOWRISYMNNSU-UHFFFAOYSA-N 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 125000001967 indiganyl group Chemical group [H][In]([H])[*] 0.000 description 1
- 239000010410 layer Substances 0.000 description 1
- 230000004298 light response Effects 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- JDSHMPZPIAZGSV-UHFFFAOYSA-N melamine Chemical compound NC1=NC(N)=NC(N)=N1 JDSHMPZPIAZGSV-UHFFFAOYSA-N 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 239000002086 nanomaterial Substances 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 229910052700 potassium Inorganic materials 0.000 description 1
- 230000006798 recombination Effects 0.000 description 1
- 238000005215 recombination Methods 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 229910052938 sodium sulfate Inorganic materials 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
- 238000006557 surface reaction Methods 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
- B01J27/24—Nitrogen compounds
-
- B01J35/39—
-
- B01J35/61—
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/04—Mixing
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
- C01B3/02—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen
- C01B3/04—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by decomposition of inorganic compounds, e.g. ammonia
- C01B3/042—Decomposition of water
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/36—Hydrogen production from non-carbon containing sources, e.g. by water electrolysis
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- Materials Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
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- General Health & Medical Sciences (AREA)
- Combustion & Propulsion (AREA)
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Abstract
The invention discloses a simple and efficient g-C lifting method3N4Method for photocatalytic hydrogen production activity at g-C3N4Directly adding alkali metal or alkaline earth metal and OH into the photocatalytic hydrogen production solution‑The ions destroy the structure of g-CN and insert metal atoms into g-C3N4Structural provisioning opportunities to alter g-C3N4The structure of the photocatalyst increases the specific surface area, improves the charge separation efficiency and enhances the photocatalytic activity. The invention uses an alkali metal or alkaline earth metal regulating solution to regulate the concentration of the G-C3N4By deprotonation, the g-C is changed3N4The partial structure of the hydrogen storage tank increases the specific surface area, improves the charge separation efficiency, and the highest hydrogen production is g-C3N4And 171 times and 3.7 times Pt/CN; in addition, the used medicine has low cost, simple operation, green and no pollution.
Description
Technical Field
The invention belongs to the technical field of photocatalysis, and particularly relates to simple and efficient g-C lifting3N4A method for preparing hydrogen activity by photocatalysis.
Background
With the energy crisis and the demand of people for good life, the preparation of clean energy by using photocatalytic technology has become one of the most popular research subjects at present. Photocatalytic technology is one of the most popular technologies in the field of catalysis, which can degrade pollutants by sunlight and convert solar energy into chemical energy. Although this field has developed rapidly over the past few decades, the development of stable and efficient hydrogen production catalysts remains a significant challenge.
Graphitic carbon nitride (g-C) as a non-metallic semiconductor material3N4) Not only has good visible light response capability, but also has excellent physicochemical properties such as good photoelectric response capability, excellent chemical and thermal stability, strong oxidation resistance, and therefore, in recent years, g-C3N4The method is widely applied to reactions such as photocatalytic hydrogen production, oxygen evolution, carbon dioxide reduction, nitrogen fixation and the like. However, the traditional precursor (urea, melamine, dicyandiamide and thiourea) produces g-C3N4The method has some defects, such as lack of active center of surface reaction, high recombination rate of photon-generated electron hole pairs, low carrier transfer efficiency and small specific surface area, and the application of the method in photocatalysis is severely limited.
To increase g-C3N4Has developed many methods including nanostructure design, element doping, and the construction of heterojunctions with other semiconductor materials. Through precursor treatment, atoms of S, Na, K, Co, Ga-Pt, Ag, B, F, P and the like are introduced into the structure of the carbon nitride through multiple times of calcination to improve the photocatalytic activity of the carbon nitride. Thus, g-C3N4Has been widely applied to photocatalytic hydrogen production, carbon dioxide reduction,Dye degradation and catalytic organic synthesis. Of these metal dopings, sodium is a very popular doping element because it is inexpensive and readily available and does not contribute to contamination. In recent years, reference has been made to sodium-doped g-C3N4There are many reports. The doping process results in g-C3N4The distortion of the plane leads to the increase of porous structures, mass transfer channels and specific surface area. However, the method has the biggest problems that the introduction steps are complex, the introduction steps are often completed in multiple steps, and impurities may be introduced in the process, so that a simpler, environment-friendly, efficient and quick hydrogen production method is needed.
Disclosure of Invention
Aiming at the problems, the invention researches a new method for improving g-C3N4The method is simple, environment-friendly, efficient, low in cost and beneficial to large-scale use.
In order to achieve the above purpose, the invention provides the following technical scheme: simple and efficient g-C lifting device3N4Method for photocatalytic hydrogen production activity at g-C3N4Directly adding alkali metal or alkaline earth metal and OH into the photocatalytic hydrogen production solution-The ions destroy the structure of g-CN and insert metal atoms into g-C3N4Structural provisioning opportunities to alter g-C3N4The structure of the photocatalyst increases the specific surface area, improves the charge separation efficiency and enhances the photocatalytic activity.
Further, the alkali metal or alkaline earth metal is NaOH, LiOH, KOH, Ca (OH)2、Ba(OH)2One of (1) and (b).
Further, said g-C3N4The method for producing hydrogen by photocatalysis comprises the following specific steps:
with g-C3N4The molecule is used as a photocatalyst, EDTA-2Na is used as a sacrificial reagent, NaOH and water are added, the temperature of the solution is controlled by a water cooling system, and H is produced after the suspension is stirred2。
Further, 10 mg of g-C was used3N4Molecular 400 mg EDTA-2Na, 0.125, 0.25, 0.375, 0.5 and 1 mmol NaOH in 50mL waterAnd (6) hydrogen production comparison.
Preferably, 0.375mmol NaOH is added per 50ml reaction solution.
Further, the solution temperature was controlled at 6 ℃ by a water cooling system, the suspension was stirred in the dark for 30 minutes, the lamp was turned on, and the evolution of H was measured by online GC every 30 minutes during HER testing2。
Further, said g-C3N4The preparation method of the photocatalyst comprises the following steps: placing 5g urea in a covered alumina crucible, heating to 550 deg.C at 5 deg.C/min from room temperature for 4 hr, cooling to room temperature, and collecting light yellow g-C3N4（g-CN）。
In the technical scheme, the invention provides the following technical effects and advantages: using alkali or alkaline earth metal conditioning solutions, by adjusting g-C3N4By deprotonation, the g-C is changed3N4The partial structure of the hydrogen storage tank increases the specific surface area, improves the charge separation efficiency, and the highest hydrogen production is g-C3N4And 171 times and 3.7 times Pt/CN; in addition, the used medicine has low cost, simple operation, green and no pollution.
Drawings
In order to more clearly illustrate the embodiments of the present application or technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments described in the present invention, and other drawings can be obtained by those skilled in the art according to the drawings.
FIG. 1 (a) g-C3N4And Na-n mmol/Pt-CN (n =0.125, 0.25, 0.375, 0.5, 1) in water with 400 mg EDTA-2Na in water simulating solar irradiation to produce H2Total amount (catalyst: 50 mg; 300W Xe lamp, optical filter lambda)>400 nm), (b) H under different conditions2Production rates, (c) cycling of the photocatalytic HER 3 times under visible light over Na-0.375mmol/Pt-CN, (d) H production when modulated with different substances2Total amount;
FIG. 2 (a) shows H at different pH values2Total amount released, (b) different Na+H at concentration2Generation of (1);
pure g-C in FIG. 33N4SEM image (b) and TEM image (e); SEM image (c) and TEM image (f) of Na-125 mmol/Pt-CN; SEM image (d) and TEM image (g) of Na-0.375 mmol/Pt-CN.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
g-C3N4In a typical process, 5g of urea was placed in a covered alumina crucible and then heated from room temperature to 550 ℃ at a rate of 5 ℃/min and held for 4 hours. After cooling to room temperature, collect the pale yellow g-C3N4（g-CN）。
Constructing a photocatalytic hydrogen production system: 10 mg of g-C are used3N4The molecular weight as photocatalyst, 400 mg EDTA-2Na (as sacrificial reagent) and NaOH test amounts (molar weight) were 0, 0.125, 0.25, 0.375, 0.5 and 1 mmol, respectively, and hydrogen production experiments were performed in 50mL of water. The solution temperature was controlled at 6 ℃ by a water cooling system. The suspension was stirred in the dark for 30 minutes and then the lamp was turned on. During HER testing, the evolved H was measured by online GC every 30 minutes2。
The hydrogen production experiment results are as follows: original g-C3N4Can only generate a small amount of H2（60 μ mol g-1h-1) No cocatalyst is added. After 1.0 wt% of Pt is added, the activity is obviously improved. For 10 mg of pure g-C3N4，H2The generation rate of the catalyst can reach 28.1 mu mol h-1. When different amounts of NaOH were added to the Pt-CN system solution, it was noted that,the Na/Pt-CN sample shows higher catalytic activity, and the activity is sequentially Na-0.375mmol/Pt-CN>Na-0.25 mmol/Pt-CN>Na-0.5 mmol/Pt-CN>Na-0.125 mmol/Pt-CN>Na-1 mmol/Pt-CN. For 10 mg of catalyst, the optimum photocatalytic hydrogen evolution efficiency of Na-0.375mmol/Pt-CN is 104.5 mu molh-1 (10454 μ mol g-1h-1) Are each g-C3N4And 171 times and 3.7 times Pt/CN (fig. 1 a, b). The stability of Na-0.375mmol/Pt-CN was investigated by cycling experiments. The system was run three times without changing the solution and photocatalyst. At the end of each operation, the hydrogen produced is evacuated. H2The yield of (c) increased linearly with irradiation time (FIG. 1 c) and the straight lines were almost parallel. In addition, we tried to control the solution with other alkali metal hydroxide or alkaline earth metal hydroxide according to the optimum amount of sodium hydroxide (0.375 mmol), and tested the activity of the photocatalyst. As shown in FIG. 1d, g-C3N4The photocatalytic activity of the modified photocatalyst is greatly improved in a modified solution. These results show that the solution control method is in g-C3N4Is effective in a photocatalytic hydrogen production system.
As shown in FIG. 1, (a) g-C3N4And Na-n mmol/Pt-CN (n =0.125, 0.25, 0.375, 0.5, 1) in water with 400 mg EDTA-2Na in water simulating solar irradiation to produce H2Total amount (catalyst: 50 mg; 300W Xe lamp, optical filter lambda)>400 nm); (b) h under different conditions2A generation rate; (c) cycling the photocatalytic HER 3 times under visible light over Na-0.375 mmol/Pt-CN; (d) h produced when using different substances for conditioning2Total amount of the components.
Na+And OH-Influence of the ions: in the presence of 10 mg of catalyst + 50ml of H2In the presence of O solution (containing 400 mg of EDTA-2Na and 1 wt% of Pt), we sought the corresponding results through a control experiment. Through Na2SO4Control of Na+And varying the molar amount of NaOH to investigate at constant Na+OH under the conditions of-Influence of ions on HER. As shown in FIG. 2a, in the absence of OH-In the case of (2), its catalytic activity is notThere is an improvement. But with the addition of NaOH, the catalytic activity gradually increased until reaching a maximum when n (NaOH) ═ 0.375mmol, and decreased as the amount of NaOH continued to increase. The results show that OH-The presence of ions enhances the catalytic activity of the carbon nitride, as is also demonstrated by the SEM and TEM results below, and the appropriate amount of NaOH modifies the structure of the carbon nitride by Na+Into g-C3N4The structure provides an opportunity. However, when the NaOH content is too large, g-C3N4The structure of (2) may be destroyed without increasing the catalytic activity. On the other hand, the pH of the solution was adjusted to 8.5 using aqueous ammonia (pH of the solution using 0.375mmol of NaOH), and a concentration gradient experiment was performed by changing Na+To verify Na+The function of (1). As shown in FIG. 2b, Na was added2SO4After that, the activity increases significantly and with Na+With increasing concentration, the activity showed a tendency to increase first and then decrease. This indicates Na+The ions may increase the activity of the Pt-CN, probably because they are embedded in the structure of the carbon nitride. When Na in the structure+When the content reaches saturation, Na is added+The content has little influence on hydrogen production.
SEM and TEM results: the images of a Scanning Electron Microscope (SEM) were clearly observed for structural changes, untreated g-C3N4The disordered, overlapped layered structure (fig. 3 b) is presented, the exposed area is limited, and therefore the specific surface area is greatly reduced, thereby having adverse effects on the light absorption efficiency and the charge migration. In contrast, g-C after treatment with 0.125 mmol NaOH3N4(FIG. 3C), the surface layer-like g-C was clearly observed3N4Significant curling has occurred and even a portion of the pores formed a clearer pore structure, and a portion of the pores with smaller radii are gradually gathering together with each other and thus transitioning toward a pore structure with larger radii, and the carbon nitride located below the surface layer may not change significantly because of the lower concentration of NaOH. When the molar amount of NaOH was raised to 0.375mmol (FIG. 3 d), more pronounced nodules were observedThe laminated structures stacked together at the same time can produce obvious bending, and the holes with smaller diameters are combined with each other to form a hole-shaped structure with larger diameter. At the same time, the data from the Transmission Electron Microscope (TEM) also demonstrate the changes that have occurred (FIGS. 3 e, f, g), the original g-C3N4The layered structures are stacked mutually, the existence of the porous structures cannot be observed, the number of the porous structures is increased along with the increase of the molar amount of NaOH, and the small holes are fused with each other to form the large holes. This structural change further enhances g-C3N4The specific surface area of the charge transfer layer is enlarged, namely the area of light absorption is expanded, the transfer distance of charges is shortened, and the transfer efficiency of the charges is improved.
And (4) conclusion: adopts NaOH to adjust a photocatalytic solution system to improve g-C3N4The performance of photocatalytic hydrogen production. The optimum amount of NaOH is 0.375 mmol. After conditioning with solution, g-C3N4The hydrogen production is stable and efficient, and the maximum hydrogen production is 3.7 times of that of Pt-CN. At the same time, the possible mechanism of NaOH regulating solution is proposed, and g-C is changed3N4The specific surface area of the sodium-containing composite material is increased, so that sodium enters g-C3N4The structure of (2) improves the catalytic activity. In addition, several other alkaline earth metals or alkali metals have also been shown to have similar effects. The method provides a new idea for the design of a photocatalytic hydrogen production system.
Although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that various changes in the embodiments and/or modifications of the invention can be made, and equivalents and modifications of some features of the invention can be made without departing from the spirit and scope of the invention.
Claims (7)
1. Simple and efficient g-C lifting device3N4The method for preparing hydrogen activity by photocatalysis is characterized by comprising the following steps: in g-C3N4Directly adding alkali metal or alkaline earth metal and OH into the photocatalytic hydrogen production solution-Ion destruction of g-CN structureFor insertion of a metal atom into g-C3N4Structural provisioning opportunities to alter g-C3N4The structure of the photocatalyst increases the specific surface area, improves the charge separation efficiency and enhances the photocatalytic activity.
2. Simple and efficient lifting g-C according to claim 13N4The method for preparing hydrogen activity by photocatalysis is characterized by comprising the following steps: the alkali metal or alkaline earth metal is NaOH, LiOH, KOH, Ca (OH)2、Ba(OH)2One of (1) and (b).
3. Simple and efficient lifting g-C according to claim 23N4The method for preparing hydrogen activity by photocatalysis is characterized by comprising the following steps: g-C3N4The photocatalytic hydrogen production method comprises the following specific steps: with g-C3N4The molecule is used as a photocatalyst, EDTA-2Na is used as a sacrificial reagent, NaOH and water are added, the temperature of the solution is controlled by a water cooling system, and H is produced after the suspension is stirred2。
4. Simple and efficient lifting g-C according to claim 33N4The method for preparing hydrogen activity by photocatalysis is characterized by comprising the following steps: 10 mg of g-C are used3N4The molecules, 400 mg EDTA-2Na, 0.125, 0.25, 0.375, 0.5 and 1 mmol NaOH, were compared in 50mL water for hydrogen production.
5. Simple and efficient lifting g-C according to claim 43N4The method for preparing hydrogen activity by photocatalysis is characterized by comprising the following steps: 0.375mmol NaOH was added per 50ml reaction solution.
6. Simple and efficient lifting g-C according to claim 33N4The method for preparing hydrogen activity by photocatalysis is characterized by comprising the following steps: the solution temperature was controlled at 6 ℃ by a water cooling system, the suspension was stirred in the dark for 30 minutes, the lamp was turned on, and the evolved H was measured by online GC every 30 minutes during the HER test2。
7. Simple and efficient lifting g-C according to claim 13N4The method for preparing hydrogen activity by photocatalysis is characterized by comprising the following steps: the g to C3N4The preparation method of the photocatalyst comprises the following steps: placing 5g urea in a covered alumina crucible, heating to 550 deg.C at 5 deg.C/min from room temperature for 4 hr, cooling to room temperature, and collecting light yellow g-C3N4（g-CN）。
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114308102A (en) * | 2021-12-23 | 2022-04-12 | 海南聚能科技创新研究院有限公司 | Metal-doped carbon nitride material and preparation method and application thereof |
| CN115155634A (en) * | 2022-03-29 | 2022-10-11 | 广州大学 | Synthesis and application of alkaline earth metal coordination modified bubbly porous g-C3N4 nanosheet photocatalyst |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114308102A (en) * | 2021-12-23 | 2022-04-12 | 海南聚能科技创新研究院有限公司 | Metal-doped carbon nitride material and preparation method and application thereof |
| CN115155634A (en) * | 2022-03-29 | 2022-10-11 | 广州大学 | Synthesis and application of alkaline earth metal coordination modified bubbly porous g-C3N4 nanosheet photocatalyst |
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