CN116770351A - Nitrogen-doped transition metal phosphide catalyst and preparation method and application thereof - Google Patents
Nitrogen-doped transition metal phosphide catalyst and preparation method and application thereof Download PDFInfo
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- 239000003054 catalyst Substances 0.000 title claims abstract description 81
- 150000003624 transition metals Chemical class 0.000 title claims abstract description 78
- 229910052723 transition metal Inorganic materials 0.000 title claims abstract description 76
- 238000002360 preparation method Methods 0.000 title abstract description 24
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 72
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 56
- 239000001257 hydrogen Substances 0.000 claims abstract description 56
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims abstract description 54
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 40
- 238000004519 manufacturing process Methods 0.000 claims abstract description 37
- 238000000034 method Methods 0.000 claims abstract description 34
- 238000005868 electrolysis reaction Methods 0.000 claims abstract description 30
- 230000008569 process Effects 0.000 claims abstract description 20
- 229910052750 molybdenum Inorganic materials 0.000 claims abstract description 8
- 239000000126 substance Substances 0.000 claims abstract description 6
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 50
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 34
- VKYKSIONXSXAKP-UHFFFAOYSA-N hexamethylenetetramine Chemical compound C1N(C2)CN3CN1CN2C3 VKYKSIONXSXAKP-UHFFFAOYSA-N 0.000 claims description 32
- 239000013535 sea water Substances 0.000 claims description 31
- 238000006243 chemical reaction Methods 0.000 claims description 25
- 229910052759 nickel Inorganic materials 0.000 claims description 22
- 239000006260 foam Substances 0.000 claims description 20
- 235000010299 hexamethylene tetramine Nutrition 0.000 claims description 16
- 239000004312 hexamethylene tetramine Substances 0.000 claims description 16
- 238000000137 annealing Methods 0.000 claims description 12
- 238000001027 hydrothermal synthesis Methods 0.000 claims description 11
- 150000002978 peroxides Chemical class 0.000 claims description 11
- 238000002156 mixing Methods 0.000 claims description 10
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims description 9
- 239000012298 atmosphere Substances 0.000 claims description 8
- 229910052698 phosphorus Inorganic materials 0.000 claims description 8
- 230000001681 protective effect Effects 0.000 claims description 8
- 239000011574 phosphorus Substances 0.000 claims description 7
- 229910052751 metal Inorganic materials 0.000 claims description 5
- 239000002184 metal Substances 0.000 claims description 5
- 239000002245 particle Substances 0.000 claims description 5
- 230000035484 reaction time Effects 0.000 claims description 3
- WQYVRQLZKVEZGA-UHFFFAOYSA-N hypochlorite Chemical compound Cl[O-] WQYVRQLZKVEZGA-UHFFFAOYSA-N 0.000 abstract description 21
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 abstract description 18
- 239000000460 chlorine Substances 0.000 abstract description 18
- JFBJUMZWZDHTIF-UHFFFAOYSA-N chlorine chlorite Inorganic materials ClOCl=O JFBJUMZWZDHTIF-UHFFFAOYSA-N 0.000 abstract description 6
- 239000000047 product Substances 0.000 description 19
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 16
- 239000002994 raw material Substances 0.000 description 14
- 229910052801 chlorine Inorganic materials 0.000 description 12
- 239000000843 powder Substances 0.000 description 12
- 239000008367 deionised water Substances 0.000 description 10
- 229910021641 deionized water Inorganic materials 0.000 description 10
- 238000005260 corrosion Methods 0.000 description 8
- 230000007797 corrosion Effects 0.000 description 8
- 238000001035 drying Methods 0.000 description 8
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 7
- 230000015572 biosynthetic process Effects 0.000 description 7
- 229910052760 oxygen Inorganic materials 0.000 description 7
- 239000001301 oxygen Substances 0.000 description 7
- ACVYVLVWPXVTIT-UHFFFAOYSA-N phosphinic acid Chemical compound O[PH2]=O ACVYVLVWPXVTIT-UHFFFAOYSA-N 0.000 description 7
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 7
- 230000009286 beneficial effect Effects 0.000 description 6
- 238000005406 washing Methods 0.000 description 6
- 229910003294 NiMo Inorganic materials 0.000 description 5
- 230000008901 benefit Effects 0.000 description 5
- 230000003197 catalytic effect Effects 0.000 description 5
- -1 hydroxide ions Chemical class 0.000 description 5
- ACVYVLVWPXVTIT-UHFFFAOYSA-M phosphinate Chemical compound [O-][PH2]=O ACVYVLVWPXVTIT-UHFFFAOYSA-M 0.000 description 5
- 238000006722 reduction reaction Methods 0.000 description 5
- YLZOPXRUQYQQID-UHFFFAOYSA-N 3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)-1-[4-[2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidin-5-yl]piperazin-1-yl]propan-1-one Chemical compound N1N=NC=2CN(CCC=21)CCC(=O)N1CCN(CC1)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F YLZOPXRUQYQQID-UHFFFAOYSA-N 0.000 description 4
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 4
- 239000011651 chromium Substances 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 239000013505 freshwater Substances 0.000 description 4
- 239000012299 nitrogen atmosphere Substances 0.000 description 4
- 230000009467 reduction Effects 0.000 description 4
- 238000003756 stirring Methods 0.000 description 4
- 238000003786 synthesis reaction Methods 0.000 description 4
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- 230000004913 activation Effects 0.000 description 3
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- 229910001120 nichrome Inorganic materials 0.000 description 3
- 238000004886 process control Methods 0.000 description 3
- 238000012546 transfer Methods 0.000 description 3
- XTEGARKTQYYJKE-UHFFFAOYSA-M Chlorate Chemical compound [O-]Cl(=O)=O XTEGARKTQYYJKE-UHFFFAOYSA-M 0.000 description 2
- 125000004429 atom Chemical group 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 229910052804 chromium Inorganic materials 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 239000012467 final product Substances 0.000 description 2
- 150000002431 hydrogen Chemical class 0.000 description 2
- 230000002401 inhibitory effect Effects 0.000 description 2
- 229910052741 iridium Inorganic materials 0.000 description 2
- GKOZUEZYRPOHIO-UHFFFAOYSA-N iridium atom Chemical compound [Ir] GKOZUEZYRPOHIO-UHFFFAOYSA-N 0.000 description 2
- GVALZJMUIHGIMD-UHFFFAOYSA-H magnesium phosphate Chemical compound [Mg+2].[Mg+2].[Mg+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O GVALZJMUIHGIMD-UHFFFAOYSA-H 0.000 description 2
- 239000004137 magnesium phosphate Substances 0.000 description 2
- 229960002261 magnesium phosphate Drugs 0.000 description 2
- 235000010994 magnesium phosphates Nutrition 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- JKQOBWVOAYFWKG-UHFFFAOYSA-N molybdenum trioxide Chemical compound O=[Mo](=O)=O JKQOBWVOAYFWKG-UHFFFAOYSA-N 0.000 description 2
- 229910052755 nonmetal Inorganic materials 0.000 description 2
- 239000007800 oxidant agent Substances 0.000 description 2
- 230000001590 oxidative effect Effects 0.000 description 2
- 229910052697 platinum Inorganic materials 0.000 description 2
- 229920000447 polyanionic polymer Polymers 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 230000001737 promoting effect Effects 0.000 description 2
- 230000008707 rearrangement Effects 0.000 description 2
- 238000006479 redox reaction Methods 0.000 description 2
- 230000002829 reductive effect Effects 0.000 description 2
- 230000027756 respiratory electron transport chain Effects 0.000 description 2
- 229910001479 sodium magnesium phosphate Inorganic materials 0.000 description 2
- 239000001488 sodium phosphate Substances 0.000 description 2
- 229910000162 sodium phosphate Inorganic materials 0.000 description 2
- RYFMWSXOAZQYPI-UHFFFAOYSA-K trisodium phosphate Chemical compound [Na+].[Na+].[Na+].[O-]P([O-])([O-])=O RYFMWSXOAZQYPI-UHFFFAOYSA-K 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- XTEGARKTQYYJKE-UHFFFAOYSA-N chloric acid Chemical compound OCl(=O)=O XTEGARKTQYYJKE-UHFFFAOYSA-N 0.000 description 1
- 229940005991 chloric acid Drugs 0.000 description 1
- 238000010612 desalination reaction Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 150000002500 ions Chemical group 0.000 description 1
- 230000036961 partial effect Effects 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 238000013112 stability test Methods 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
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- Catalysts (AREA)
- Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
Abstract
The invention provides a nitrogen-doped transition metal phosphide catalyst, and a preparation method and application thereof. The nitrogen-doped transition metal phosphide catalyst according to the present invention has the chemical formula: N-NiA x P, wherein the transition metal A comprises at least one of Mo, ti, mn, cr, x is more than or equal to 3, and the nitrogen doped transition metal phosphide catalyst has a porous structure. Not only improves the hydrogen production efficiency, prolongs the service life of equipment and reduces the hydrogen production cost, but also ensures that the electrolysis process is carried out under low voltage, inhibits the generation of chlorine and hypochlorite and promotes the wide utilization of hydrogen energy. The invention also provides a preparation method and application of the catalyst.
Description
Technical Field
The invention belongs to the technical field of hydrogen production by water electrolysis, and particularly relates to a nitrogen-doped transition metal phosphide catalyst, and a preparation method and application thereof.
Background
The energy density of hydrogen is very high, and no carbon is discharged after the reaction, so that the hydrogen is the best substitute for fossil energy. Electrolytic fresh water hydrogen production is the most convenient hydrogen generation way. However, the fresh water resources are limited, and a large amount of the fresh water resources are used for electrolytic hydrogen production to induce fresh water reserve pressure. Seawater accounts for 96.5% of the total world water resources, and the reserves are extremely rich. However, in the current process of directly electrolyzing seawater to prepare hydrogen, desalination of seawater is needed, so that energy consumption and cost are too high. Therefore, the development of a catalyst with high efficiency, low cost and stable performance for the technology of directly electrolyzing seawater to prepare hydrogen is very critical, and is the best choice for determining the high-efficiency utilization of clean energy of hydrogen energy.
The direct electrolysis of seawater for hydrogen production is the best choice for storing clean energy, however, in the direct electrolysis of seawater for hydrogen production, the existence of chloride ions can affect the reduction reaction of oxygen, reduce the hydrogen production efficiency, and the generation of chlorine causes serious electrode corrosion of electrolysis equipment, so that the efficiency of the electrolysis of seawater for hydrogen production can be seriously affected, the service life of equipment can be reduced, and the hydrogen production cost can be increased. In addition, under high electrolysis voltage, the interaction of chlorine and hydroxide ions forms hypochlorite and other components, which also seriously affect the stable operation of the equipment.
Therefore, a new catalyst needs to be developed, which not only can greatly improve the hydrogen production efficiency, prolong the service life of equipment and reduce the hydrogen production cost, but also can ensure that the electrolysis process is carried out under low voltage, inhibit the generation of chlorine and hypochlorite and promote the wide utilization of hydrogen energy.
Disclosure of Invention
The present invention aims to solve at least one of the above technical problems in the prior art. Therefore, the invention provides the nitrogen-doped transition metal phosphide catalyst, which not only improves the hydrogen production efficiency, prolongs the service life of equipment and reduces the hydrogen production cost, but also ensures that the electrolysis process is carried out under low voltage, inhibits the generation of chlorine and hypochlorite and promotes the wide utilization of hydrogen energy.
The invention also provides a method for preparing the nitrogen-doped transition metal phosphide catalyst.
The invention also provides application of the nitrogen-doped transition metal phosphide catalyst in hydrogen production by seawater electrolysis.
The inventionIn a first aspect, a nitrogen-doped transition metal phosphide catalyst is provided, having the chemical formula: N-NiA x P, wherein the transition metal A comprises at least one of Mo, ti, mn, cr, x is more than or equal to 3, and the nitrogen doped transition metal phosphide catalyst has a porous structure.
The invention relates to one of the technical schemes of nitrogen doped transition metal phosphide catalysts, which has at least the following beneficial effects:
the catalyst for producing hydrogen by water electrolysis generally uses platinum and iridium as main components, and has high price. The catalyst of the invention adopts low-cost transition metal as a synthetic raw material, and has the advantages of low raw material price and low cost.
The composition of general transition metal phosphide is adjustable, and the phosphide has the characteristics of high catalytic activity, but the stability is not ideal enough, and the catalytic activity is limited. In the catalyst, ni and N initiate rearrangement of electrons outside transition metal cores, so that the conductivity and the length of metal-nonmetal bonds are improved, and the metal-nitrogen bonds have higher electronegativity, so that the stability of active sites is improved through electron withdrawing capability, metal atoms obtain higher valence states, thereby improving electron transfer and the electron density of the catalyst, resisting seawater corrosion, and having very good stability.
OER is the main reaction occurring when water electrolysis is used for hydrogen production, and the product is oxygen; CER is a reaction occurring in the process of hydrogen production by seawater electrolysis, the product contains a large amount of chlorine, the CER and OER compete, the benefits of the hydrogen production by seawater electrolysis are seriously hampered, equipment corrosion is serious, hypochlorite formed by chlorine and hydroxide ions is attached to an electrode, and the equipment cannot stably run for a long time, so that OER needs to be catalyzed under low overpotential, the hydrogen production by seawater electrolysis is realized under low potential limit, and CER is avoided.
The catalyst of the invention is prepared by N-NiMo 3 P is exemplified by the fact that the overpotential required to initiate anodic oxygen evolution (Oxygen evolution reaction, OER) in seawater is 385mV, which is significantly less than the 490mV overpotential required to initiate reduction of chlorine (Chlorine evolution reaction, CER), thereby effectively preventing reduction of hypochlorite ions and chlorateThe surface modification of the polyanion in which chloric acid is used as a core will further help to avoid CER. Finally solves the problem that the electrode of the electrolysis equipment is seriously corroded due to the generation of chlorine when the catalyst is used for preparing hydrogen by electrolyzing seawater.
The nitrogen-doped transition metal phosphide catalyst disclosed by the invention has a porous structure, is beneficial to the porous structure, not only allows faster mass transmission, but also introduces additional active sites into dangling bond sites at the edge of a pore, and improves the activity of the catalyst.
According to some embodiments of the invention, the nitrogen-doped transition metal phosphide catalyst has a particle size in the range of 40nm to 80nm.
The particle size range is 40 nm-80 nm, belongs to the nano-scale, is beneficial to mass transmission and introduction of more active sites, and improves the activity.
According to some embodiments of the invention, a is one of Mo, ti, mn, cr.
According to some embodiments of the invention, a is two of Mo, ti, mn, cr.
In a second aspect, the present invention provides a method for preparing the nitrogen-doped transition metal phosphide catalyst, comprising the steps of:
s1: adding a nitrogen source, a peroxide solution of the transition metal A and foam nickel into a reaction kettle for hydrothermal reaction;
s2: annealing the product of the step S1 under a protective atmosphere;
s3: and (3) mixing the product of the step (S2) with a phosphorus source, and performing phosphating treatment under a protective atmosphere.
The invention relates to a technical scheme in a preparation method of a nitrogen-doped transition metal phosphide catalyst, which has at least the following beneficial effects:
according to the preparation method, the nitrogen source, the peroxide solution of the transition metal A and the foam nickel are used as raw materials for reaction, so that the process is simpler and more convenient.
According to the preparation method, foam nickel is used as one of the preparation raw materials, and the prepared catalyst has a nanoscale size and a porous structure, and is good in activation performance, high in mass transfer efficiency, corrosion-resistant and long in service life.
The catalyst prepared by the preparation method provided by the invention has lower cost when used for directly preparing hydrogen by electrolysis of seawater.
The preparation method of the invention does not need expensive equipment and complex process control, has low reaction conditions, easily obtained raw materials, low production cost and easy industrial production.
According to some embodiments of the invention, the nitrogen source comprises Hexamethylenetetramine (HMTA).
According to some embodiments of the invention, the nitrogen source comprises HMTA solution.
The HMTA is used as a nitrogen source, so that the proportion of each element can be ensured, and the quality of the synthesized components is ensured.
HMTA acts as a nitrogen source for generating a transition metal to nitrogen bond, i.e., an a-N bond.
According to some embodiments of the invention, the method for preparing the peroxide solution of transition metal a comprises: and mixing and reacting the transition metal A with hydrogen peroxide.
The transition metal A is oxidized by hydrogen peroxide to form oxide, and the process is simpler and more convenient.
According to some embodiments of the invention, the transition metal a is in powder form.
The mixing ratio range of the powder of the transition metal A and the hydrogen peroxide is directly related to the highest valence of the transition metal A, wherein in order to ensure that the powder of the transition metal A is completely oxidized by the hydrogen peroxide, the mol ratio of the powder of the transition metal A to the hydrogen peroxide is higher than 1:3.5, the powder of the transition metal A and the hydrogen peroxide undergo oxidation-reduction reaction, the hydrogen peroxide is an oxidant, and the solution becomes a peroxide solution of the transition metal.
The reaction that occurs, taking Cr as an example, is: cr+3H 2 O 2＝ CrO 3 +3H 2 O。
According to some embodiments of the invention, the molar ratio of the nitrogen source to the nickel foam is: nitrogen source, foam nickel >0.5.
The final synthesis target is N-NiA x P, wherein the atomic ratio of N to Ni is 1:1, but in the synthesis, N in the nitrogen source (e.g., HMTA) does not fully participate in the reaction with Ni, so the molar ratio of nitrogen source to nickel foam needs to be greater than 0.5 to ensure that Ni is fully bonded to N.
Nickel foam has two main roles, one is to provide a source of nickel in the final life product, and the other is to act as a template for the micron-sized porous sheet for the final product formation.
According to some embodiments of the invention, the temperature of the hydrothermal reaction is 200 ℃ to 300 ℃.
According to some embodiments of the invention, the hydrothermal reaction time is 20h to 30h.
According to some embodiments of the invention, the annealing temperature is 350 ℃ to 450 ℃.
According to some embodiments of the invention, the annealing time is 2-3 hours.
The annealing process can promote the performance of the catalyst.
According to some embodiments of the invention, the phosphorus source comprises hypophosphorous acid and hypophosphite.
According to some embodiments of the invention, the hypophosphite comprises sodium phosphate and magnesium phosphate.
Hypophosphorous acid and hypophosphite are used as phosphorus sources, and are not red phosphorus and the like, so that the stability and the price of the raw materials are better.
According to some embodiments of the invention, the temperature of the phosphating treatment is 350 ℃ to 450 ℃.
According to some embodiments of the invention, the phosphating is for a period of time ranging from 3 hours to 5 hours.
According to some embodiments of the invention, the protective atmosphere comprises nitrogen.
According to some embodiments of the invention, the method further comprises, between steps S1 and S2, drying the product of step S1 in a vacuum oven at 40-60 ℃ for 24 hours after washing it with deionized water.
According to some embodiments of the invention, the method further comprises, after step S3, drying the product of step S3 in a vacuum oven at 40 ℃ for 24 hours after washing with deionized water sufficiently.
The third aspect of the invention provides the application of the nitrogen-doped transition metal phosphide catalyst in hydrogen production by seawater electrolysis.
The invention relates to a technical scheme of an application of a nitrogen-doped transition metal phosphide catalyst in the hydrogen production of electrolytic seawater, which has at least the following beneficial effects:
the nitrogen-doped transition metal phosphide catalyst disclosed by the invention is used for directly producing hydrogen by electrolyzing seawater, so that the hydrogen production efficiency is improved, the equipment service life is prolonged, the hydrogen production cost is reduced, the electrolysis process can be ensured to be carried out at low voltage, the generation of chlorine and hypochlorite is inhibited, and the wide utilization of hydrogen energy is promoted.
Drawings
FIG. 1 is a schematic illustration of a process for preparing a catalyst of the present invention.
FIG. 2 shows the catalyst and IrO of example 1 and example 2 2 LSV curve of catalyst.
FIG. 3 shows the catalyst and IrO of example 1 and example 2 2 The catalyst was tested for 96h stability test results.
Detailed Description
The following are specific embodiments of the present invention, and the technical solutions of the present invention will be further described with reference to the embodiments, but the present invention is not limited to these embodiments.
In some embodiments of the present invention, the present invention provides a nitrogen-doped transition metal phosphide catalyst having the chemical formula: N-NiA x P, wherein the transition metal A comprises at least one of Mo, ti, mn, cr, x is more than or equal to 3, and the nitrogen doped transition metal phosphide catalyst has a porous structure.
It is understood that the catalyst for producing hydrogen by water electrolysis generally uses platinum and iridium as main components, and is high in cost. The catalyst of the invention adopts low-cost transition metal as a synthetic raw material, and has the advantages of low raw material price and low cost. The composition of general transition metal phosphide is adjustable, and the phosphide has the characteristics of high catalytic activity, but the stability is not ideal enough, and the catalytic activity is limited. In the catalyst, ni and N initiate rearrangement of electrons outside transition metal cores, so that the conductivity and the length of metal-nonmetal bonds are improved, and the metal-nitrogen bonds have higher electronegativity, so that the stability of active sites is improved through electron withdrawing capability, metal atoms obtain higher valence states, thereby improving electron transfer and the electron density of the catalyst, resisting seawater corrosion, and having very good stability.
It is also understood that OER is the primary reaction that occurs when water electrolysis is used to produce hydrogen, and the product is oxygen; CER is a reaction occurring in the process of hydrogen production by seawater electrolysis, the product contains a large amount of chlorine, the CER and OER compete, the benefits of the hydrogen production by seawater electrolysis are seriously hampered, equipment corrosion is serious, hypochlorite formed by chlorine and hydroxide ions is attached to an electrode, and the equipment cannot stably run for a long time, so that OER needs to be catalyzed under low overpotential, the hydrogen production by seawater electrolysis is realized under low potential limit, and CER is avoided. The catalyst of the invention is prepared by N-NiMo 3 P is exemplified by the over-potential required to initiate anodic oxygen evolution (Oxygen evolution reaction, OER) in seawater being 385mV, significantly less than the 490mV over-potential required to initiate reduction of chlorine (Chlorine evolution reaction, CER), whereby reduction of hypochlorite and chlorate formation can be effectively prevented, wherein surface modification of chloric acid-cored polyanions will further help to avoid CER. Finally solves the problem that the electrode of the electrolysis equipment is seriously corroded due to the generation of chlorine when the catalyst is used for preparing hydrogen by electrolyzing seawater.
It should be noted that the nitrogen-doped transition metal phosphide catalyst of the present invention has a porous structure, which not only allows for faster mass transport, but also introduces additional active sites at dangling bond sites at the pore edges, which is beneficial to improving the activity of the catalyst.
In some embodiments of the invention, the particle size of the nitrogen-doped transition metal phosphide catalyst ranges from 40nm to 80nm.
It can be understood that the particle size range is 40 nm-80 nm, belongs to the nano-scale, is favorable for improving the utilization rate of the catalytic inner surface, increases the reaction rate, and can reduce the catalyst dosage.
In some embodiments of the invention, a is one of Mo, ti, mn, cr.
In some embodiments of the invention, a is two of Mo, ti, mn, cr.
In still other embodiments of the present invention, the present invention provides a method of preparing the nitrogen-doped transition metal phosphide catalyst of the present invention, comprising the steps of:
s1: adding a nitrogen source, a peroxide solution of the transition metal A and foam nickel into a reaction kettle for hydrothermal reaction;
s2: annealing the product of the step S1 under a protective atmosphere;
s3: and (3) mixing the product of the step (S2) with a phosphorus source, and performing phosphating treatment under a protective atmosphere.
It can be understood that the preparation method of the invention takes the nitrogen source, the peroxide solution of the transition metal A and the foam nickel as raw materials for reaction, and the process is simpler and more convenient.
Furthermore, the catalyst prepared by the preparation method provided by the invention has the advantages of nanoscale size, porous structure, good activation performance, high mass transfer efficiency, corrosion resistance and long service life.
Furthermore, the catalyst prepared by the preparation method provided by the invention has lower cost when being used for directly preparing hydrogen by electrolyzing seawater.
It can also be appreciated that the preparation method of the invention does not need expensive equipment and complex process control, has no harsh reaction conditions, easily obtained raw materials, low production cost and easy industrial production.
In some embodiments of the invention, the nitrogen source comprises Hexamethylenetetramine (HMTA).
In some embodiments of the invention, the nitrogen source comprises a HMTA solution.
In some embodiments of the invention, the concentration of HMTA solution is 99%, which may be considered pure.
The HMTA is used as a nitrogen source, so that the proportion of each element can be ensured, and the quality of the synthesized components is ensured.
HMTA acts as a nitrogen source for generating a transition metal to nitrogen bond, i.e., an a-N bond.
In some embodiments of the invention, the peroxide solution of transition metal a is prepared by: mixing transition metal A with hydrogen peroxide for reaction.
The transition metal A is oxidized by hydrogen peroxide to form oxide, and the process is simpler and more convenient.
In some embodiments of the invention, the transition metal a is in powder form.
The mixing ratio range of the powder of the transition metal A and the hydrogen peroxide is directly related to the highest valence of the transition metal A, wherein in order to ensure that the powder of the transition metal A is completely oxidized by the hydrogen peroxide, the mol ratio of the powder of the transition metal A to the hydrogen peroxide is higher than 1:3.5, the powder of the transition metal A and the hydrogen peroxide undergo oxidation-reduction reaction, the hydrogen peroxide is an oxidant, and the solution becomes a peroxide solution of the transition metal.
The reaction that occurs, taking Cr as an example, is: cr+3H 2 O 2＝ CrO 3 +3H 2 O。
In some embodiments of the invention, the molar ratio of nitrogen source to nickel foam is: nitrogen source, foam nickel >0.5.
The final synthesis target is N-NiA x P, wherein the atomic ratio of N to Ni is 1:1, but in the synthesis, N in the nitrogen source (e.g., HMTA) does not fully participate in the reaction with Ni, so the molar ratio of nitrogen source to nickel foam needs to be greater than 0.5 to ensure that Ni is fully bonded to N.
Nickel foam has two main roles, one is to provide a source of nickel in the final life product, and the other is to act as a template for the micron-sized porous sheet for the final product formation.
In some embodiments of the invention, the temperature of the hydrothermal reaction is 200 ℃ to 300 ℃.
In some embodiments of the invention, the hydrothermal reaction time is 20h to 30h.
In some embodiments of the invention, the temperature of the anneal is 350 ℃ to 450 ℃.
In some embodiments of the invention, the time of annealing is 2h to 3h.
The annealing process can promote the performance of the catalyst.
In some embodiments of the invention, the phosphorus source includes hypophosphorous acid and hypophosphites.
In some embodiments of the invention, the hypophosphite comprises sodium phosphate and magnesium phosphate.
Hypophosphorous acid and hypophosphite are used as phosphorus sources, and are not red phosphorus and the like, so that the stability and the price of the raw materials are better.
In some embodiments of the invention, the temperature of the phosphating treatment is 350 ℃ to 450 ℃.
In some embodiments of the invention, the phosphating is for a period of 3 hours to 5 hours.
In some embodiments of the invention, the protective atmosphere comprises nitrogen.
In some embodiments of the invention, the method further comprises, between steps S1 and S2, drying the product of step S1 in a vacuum oven at 40℃to 60℃for 24 hours after washing with deionized water sufficiently.
In some embodiments of the invention, the method further comprises, after step S3, drying the product of step S3 in a vacuum oven at 40 ℃ for 24 hours after washing the product with deionized water.
In other embodiments of the invention, the invention provides the use of nitrogen-doped transition metal phosphide catalysts in the production of hydrogen from electrolysis of seawater.
It can be understood that the nitrogen-doped transition metal phosphide catalyst of the invention is used for directly producing hydrogen by electrolyzing seawater, thereby not only improving the hydrogen production efficiency, prolonging the service life of equipment and reducing the hydrogen production cost, but also ensuring that the electrolysis process is carried out under low voltage, inhibiting the generation of chlorine and hypochlorite and promoting the wide utilization of hydrogen energy.
The preparation flow of the catalyst of the present invention can be shown with reference to fig. 1.
The technical solution of the present invention will be better understood in conjunction with the following specific examples.
Example 1
The embodiment provides a nitrogen-doped transition metal phosphide catalyst, which has a chemical general formula: N-NiCr 3 P, nitrogen doped transition metal phosphide catalysts having multiplePore structure.
The specific preparation method comprises the following steps:
taking 7mL of hydrogen peroxide with the mass percentage exceeding 40%, dripping into 325mg of metal chromium powder, and continuously stirring in the process to form yellow chromium peroxide solution;
520mg of HMTA was dissolved with 10mL of deionized water and added to the chromium peroxide solution simultaneously with 385mg of nickel foam, the process was continued with stirring for 1h;
transferring the solution into an autoclave, continuously performing hydrothermal reaction for 24 hours at 200 ℃, and naturally cooling to room temperature;
then, fully washing the product by deionized water and ethanol, and drying the obtained powder sample in a vacuum drying oven at 40 ℃ for 24 hours;
after drying, annealing the sample in a tube furnace at 350 ℃ for 2 hours under nitrogen atmosphere, then fully mixing the sample with 3.9g of hypophosphorous acid, and phosphating for 4 hours under nitrogen atmosphere at the constant temperature of 400 ℃;
then, the sample is washed by deionized water and dried in a vacuum drying oven at 40 ℃ for 24 hours, thus obtaining the finished product.
Example 2
The embodiment provides a nitrogen-doped transition metal phosphide catalyst, which has a chemical general formula: N-NiMo 3 The P, nitrogen doped transition metal phosphide catalyst has a porous structure.
The specific preparation method comprises the following steps:
7mL of hydrogen peroxide with the mass percentage exceeding 40% is dripped into 600mg of metal molybdenum powder, and stirring is continuously carried out in the process to form yellow molybdenum peroxide solution;
520mg of HMTA was dissolved with 10mL of deionized water and added to the molybdenum peroxide solution simultaneously with 385mg of nickel foam, with stirring for 1 hour;
transferring the solution into an autoclave, continuously performing hydrothermal reaction for 24 hours at 200 ℃, and naturally cooling to room temperature;
then, fully washing the product by deionized water and ethanol, and drying the obtained powder sample in a vacuum drying oven at 40 ℃ for 24 hours;
after drying, annealing the sample in a tube furnace at 350 ℃ for 3 hours under nitrogen atmosphere, then fully mixing the sample with 4.8g of hypophosphorous acid, and phosphating for 4 hours under nitrogen atmosphere at the constant temperature of 400 ℃;
then, the sample is washed by deionized water and dried in a vacuum drying oven at 40 ℃ for 24 hours, thus obtaining the finished product.
Test case
The catalysts prepared in example 1 and example 2 were tested for performance using a swiss vantage electrochemical workstation (swiss vantage model, PGSTAT 302N) and used for direct hydrogen production experiments with electrolyzed seawater, respectively.
The specific test method comprises the following steps:
N-NiCr prepared in example 1 was used respectively 3 P and N-NiMo prepared in example 2 3 P as cathode and anode catalyst, with IrO 2 The LSV curves were tested using an electrochemical workstation in comparison with Pt/C (anode catalyst).
FIG. 2 shows the catalyst and IrO of example 1 and example 2 2 Partial LSV curve of catalyst.
Referring to FIG. 2, it can be seen that the catalyst of example 1 only needs to reach a stable 10mA/cm at 352mV 2 。
The catalyst of example 2 only required a steady 10mA/cm at 346mV 2 。
While the common catalyst IrO 2 To achieve the same effect, the required voltage was 385mV.
I.e. when the current reaches 10mA/cm 2 At the time of IrO 2 、N-NiCr 3 P、N-NiMo 3 The overpotential of P was 385mV,352mV and 346mV, respectively.
The overpotential calculation formula: e Overpotential (OER) =e (vvs.rhe) -1.23.
FIG. 3 shows the IrO reaction with the catalyst prepared in example 1 and example 2 2 And current density plot after 96h of Pt/C catalyst tested under the same conditions.
Referring to FIG. 3, the catalyst stability of both example 1 and example 2 was better than IrO 2 And Pt/C.
The invention also provides a preparation method and application of the nitrogen-doped transition metal phosphide catalyst.
Specifically, the preparation method of the invention takes the nitrogen source, the peroxide solution of the transition metal A and the foam nickel as raw materials for reaction, and the process is simpler and more convenient.
In addition, the preparation method of the invention takes the foam nickel as one of the preparation raw materials, and the prepared catalyst has nano-scale size and porous structure, good activation performance, high mass transfer efficiency, corrosion resistance and long service life.
The catalyst prepared by the preparation method provided by the invention has lower cost when used for directly preparing hydrogen by electrolysis of seawater.
The preparation method of the invention does not need expensive equipment and complex process control, has low reaction conditions, easily obtained raw materials, low production cost and easy industrial production.
It can be understood that the nitrogen-doped transition metal phosphide catalyst of the invention is used for directly producing hydrogen by electrolyzing seawater, thereby not only improving the hydrogen production efficiency, prolonging the service life of equipment and reducing the hydrogen production cost, but also ensuring that the electrolysis process is carried out under low voltage, inhibiting the generation of chlorine and hypochlorite and promoting the wide utilization of hydrogen energy.
The present invention has been described in detail with reference to the embodiments, but the present invention is not limited to the embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the spirit of the present invention.
Claims (10)
1. A nitrogen-doped transition metal phosphide catalyst characterized by the chemical formula: N-NiA x P, wherein the transition metal A comprises at least one of Mo, ti, mn, cr, x is more than or equal to 3, and the nitrogen doped transition metal phosphide catalyst has a porous structure.
2. The nitrogen-doped transition metal phosphide catalyst according to claim 1, characterized in that the particle size of the nitrogen-doped transition metal phosphide catalyst is in the range of 40nm to 80nm.
3. A method of preparing the nitrogen-doped transition metal phosphide catalyst as recited in claim 1 or 2, comprising the steps of:
s1: adding a nitrogen source, a peroxide solution of the transition metal A and foam nickel into a reaction kettle for hydrothermal reaction;
s2: annealing the product of the step S1 under a protective atmosphere;
s3: and (3) mixing the product of the step (S2) with a phosphorus source, and performing phosphating treatment under a protective atmosphere.
4. A method according to claim 3, wherein the nitrogen source comprises hexamethylenetetramine.
5. A process according to claim 3, wherein the peroxide solution of transition metal a is prepared by: and mixing and reacting the metal corresponding to the transition metal A with hydrogen peroxide.
6. A method according to claim 3, wherein the molar ratio of nitrogen source to nickel foam is: nitrogen source, foam nickel >0.5.
7. A method according to claim 3, wherein the temperature of the hydrothermal reaction is 200 ℃ to 300 ℃; and/or the hydrothermal reaction time is 20-30 h.
8. A method according to claim 3, wherein the temperature of the annealing is from 350 ℃ to 450 ℃; and/or the annealing time is 2-3 h.
9. A method according to claim 3, wherein the temperature of the phosphating treatment is between 350 ℃ and 450 ℃; and/or the phosphating treatment time is 3-5 h.
10. Use of a nitrogen-doped transition metal phosphide catalyst as claimed in claim 1 or 2 in the electrolysis of seawater for hydrogen production.
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