CN117888120A - Electrolytic reduction method for regulating valence state of vanadium electrolyte - Google Patents
Electrolytic reduction method for regulating valence state of vanadium electrolyte Download PDFInfo
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- 229910052720 vanadium Inorganic materials 0.000 title claims abstract description 83
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 title claims abstract description 82
- 239000003792 electrolyte Substances 0.000 title claims abstract description 54
- 238000000034 method Methods 0.000 title claims abstract description 46
- 230000001105 regulatory effect Effects 0.000 title claims abstract description 12
- 238000005868 electrolysis reaction Methods 0.000 claims abstract description 106
- 239000007789 gas Substances 0.000 claims abstract description 64
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims abstract description 56
- 238000009792 diffusion process Methods 0.000 claims abstract description 41
- 239000012528 membrane Substances 0.000 claims abstract description 39
- 238000006243 chemical reaction Methods 0.000 claims abstract description 31
- 239000007864 aqueous solution Substances 0.000 claims abstract description 30
- 239000001257 hydrogen Substances 0.000 claims abstract description 28
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 28
- 238000006722 reduction reaction Methods 0.000 claims abstract description 26
- 229910001456 vanadium ion Inorganic materials 0.000 claims abstract description 22
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims abstract description 21
- 239000007788 liquid Substances 0.000 claims abstract description 9
- 238000007254 oxidation reaction Methods 0.000 claims abstract description 9
- 150000002431 hydrogen Chemical class 0.000 claims abstract description 7
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 48
- 229910052799 carbon Inorganic materials 0.000 claims description 26
- UUUGYDOQQLOJQA-UHFFFAOYSA-L vanadyl sulfate Chemical compound [V+2]=O.[O-]S([O-])(=O)=O UUUGYDOQQLOJQA-UHFFFAOYSA-L 0.000 claims description 26
- 229940041260 vanadyl sulfate Drugs 0.000 claims description 26
- 229910000352 vanadyl sulfate Inorganic materials 0.000 claims description 26
- 238000011068 loading method Methods 0.000 claims description 21
- 229910002804 graphite Inorganic materials 0.000 claims description 20
- 239000010439 graphite Substances 0.000 claims description 20
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 16
- 230000003197 catalytic effect Effects 0.000 claims description 15
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 claims description 13
- 229920005989 resin Polymers 0.000 claims description 11
- 239000011347 resin Substances 0.000 claims description 11
- 125000002091 cationic group Chemical group 0.000 claims description 10
- 239000003575 carbonaceous material Substances 0.000 claims description 9
- 239000003054 catalyst Substances 0.000 claims description 9
- 239000011230 binding agent Substances 0.000 claims description 8
- 239000004744 fabric Substances 0.000 claims description 8
- 239000007769 metal material Substances 0.000 claims description 8
- DSVGQVZAZSZEEX-UHFFFAOYSA-N [C].[Pt] Chemical compound [C].[Pt] DSVGQVZAZSZEEX-UHFFFAOYSA-N 0.000 claims description 7
- 239000000203 mixture Substances 0.000 claims description 7
- 229910052763 palladium Inorganic materials 0.000 claims description 7
- 229920000557 Nafion® Polymers 0.000 claims description 6
- -1 polytetrafluoroethylene Polymers 0.000 claims description 5
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 5
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 5
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 4
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 4
- UKVIEHSSVKSQBA-UHFFFAOYSA-N methane;palladium Chemical compound C.[Pd] UKVIEHSSVKSQBA-UHFFFAOYSA-N 0.000 claims description 4
- 229910052697 platinum Inorganic materials 0.000 claims description 4
- 229910052709 silver Inorganic materials 0.000 claims description 4
- 239000004332 silver Substances 0.000 claims description 4
- 229910052719 titanium Inorganic materials 0.000 claims description 4
- 239000010936 titanium Substances 0.000 claims description 4
- LSGOVYNHVSXFFJ-UHFFFAOYSA-N vanadate(3-) Chemical compound [O-][V]([O-])([O-])=O LSGOVYNHVSXFFJ-UHFFFAOYSA-N 0.000 claims description 4
- 150000001768 cations Chemical class 0.000 claims description 3
- LSNNMFCWUKXFEE-UHFFFAOYSA-M Bisulfite Chemical compound OS([O-])=O LSNNMFCWUKXFEE-UHFFFAOYSA-M 0.000 claims description 2
- 239000006260 foam Substances 0.000 claims description 2
- 229910021397 glassy carbon Inorganic materials 0.000 claims description 2
- 239000012982 microporous membrane Substances 0.000 claims description 2
- 238000010349 cathodic reaction Methods 0.000 claims 1
- HTXDPTMKBJXEOW-UHFFFAOYSA-N dioxoiridium Chemical compound O=[Ir]=O HTXDPTMKBJXEOW-UHFFFAOYSA-N 0.000 abstract description 20
- 229910000457 iridium oxide Inorganic materials 0.000 abstract description 20
- 229910000510 noble metal Inorganic materials 0.000 abstract description 5
- 238000005265 energy consumption Methods 0.000 abstract description 3
- VLOPEOIIELCUML-UHFFFAOYSA-L vanadium(2+);sulfate Chemical compound [V+2].[O-]S([O-])(=O)=O VLOPEOIIELCUML-UHFFFAOYSA-L 0.000 description 11
- 230000000052 comparative effect Effects 0.000 description 10
- 238000002360 preparation method Methods 0.000 description 9
- 238000010586 diagram Methods 0.000 description 6
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 4
- 239000010406 cathode material Substances 0.000 description 4
- 229910052741 iridium Inorganic materials 0.000 description 4
- GKOZUEZYRPOHIO-UHFFFAOYSA-N iridium atom Chemical compound [Ir] GKOZUEZYRPOHIO-UHFFFAOYSA-N 0.000 description 4
- 239000001301 oxygen Substances 0.000 description 4
- 229910052760 oxygen Inorganic materials 0.000 description 4
- 239000013543 active substance Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 238000011946 reduction process Methods 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- KZEVSDGEBAJOTK-UHFFFAOYSA-N 1-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)-2-[5-[2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidin-5-yl]-1,3,4-oxadiazol-2-yl]ethanone Chemical compound N1N=NC=2CN(CCC=21)C(CC=1OC(=NN=1)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)=O KZEVSDGEBAJOTK-UHFFFAOYSA-N 0.000 description 1
- HFJHNGKIVAKCIW-UHFFFAOYSA-N Stearyl monoglyceridyl citrate Chemical compound OCC(O)CO.OC(=O)CC(O)(CC(O)=O)CC(O)=O.CCCCCCCCCCCCCCCCCC(O)=O HFJHNGKIVAKCIW-UHFFFAOYSA-N 0.000 description 1
- 239000011149 active material Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 239000011494 foam glass Substances 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- WQEVDHBJGNOKKO-UHFFFAOYSA-K vanadic acid Chemical compound O[V](O)(O)=O WQEVDHBJGNOKKO-UHFFFAOYSA-K 0.000 description 1
- 125000005287 vanadyl group Chemical group 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Abstract
The invention discloses an electrolytic reduction method for regulating valence state of vanadium electrolyte, which takes oxidation reaction of hydrogen as anode reaction, reduction reaction of vanadium ion as cathode reaction, and sulfuric acid aqueous solution as electrolyte for electrolysis, and regulates the valence of 4 or 5 vanadium electrolyte to valence 3. According to the invention, the hydrogen oxidation reaction is used as an anode reaction, and a membrane electrode or a gas diffusion electrode is preferably used as an anode, so that an iridium oxide anode is not used, and the cost of noble metal on the anode is effectively reduced (reduced to 1/8-1/40); the electrolysis voltage was reduced by about 1.5V (compared to iridium oxide anode). The invention can be carried out in a diaphragm mode (anode liquid can be used for a long time) and in a diaphragm-free mode, and can obviously improve the current efficiency (8.9% -28.4%) and reduce the electrolysis energy consumption (more than 70%).
Description
Field of the art
The invention relates to an electrolytic reduction method for regulating valence state of vanadium electrolyte, which belongs to the field of electrolytic synthesis, in particular to an electrolytic reduction method for regulating valence state of vanadium electrolyte by taking oxidation reaction of hydrogen as anode reaction and reduction reaction of vanadium ion as cathode reaction.
(II) background art
The all-vanadium redox flow battery is a redox battery taking vanadium as an active material and in a circulating flowing liquid state. The initial electrolyte of the battery is sulfuric acid aqueous solution containing 3-valent vanadium ions and 4-valent vanadium ions (the concentration of the 3-valent vanadium ions and the concentration of the 4-valent vanadium ions are close), or the sulfuric acid aqueous solution containing 3-valent vanadium ions and the 4-valent vanadium ions are respectively used as the initial electrolyte of the cathode chamber and the anode chamber. The electrolytic reduction method is an important method for regulating the valence state of the vanadium electrolyte (usually reducing from 5 valence or 4 valence to 3 valence), and has the advantages of high efficiency, accuracy and the like. Currently, in industry, the electrolytic reduction method for valence state adjustment of vanadium electrolyte mainly uses oxygen evolution reaction as an auxiliary reaction. It is well known that iridium oxide anodes (typically titanium-plated iridium oxide electrodes) are the best oxygen evolution anodes, not only with very low oxygen evolution overpotential but also with very stable performance. Therefore, iridium oxide anodes are commonly used in electrolytic reduction processes for valence state adjustment of vanadium electrolytes. The service life of the iridium oxide anode is basically in direct proportion to the iridium content on the electrode, and the iridium oxide electrode with the iridium content of 10 g/square meter is 1000A/m 2 Under the current density, the service life can reach about 2 years. Therefore, the loss of iridium oxide anode is one of the main costs of the electrolytic reduction process for valence state adjustment of vanadium electrolyte. In the early 2021, the price of iridium metal increased from 400 to 1500 yuan/g, so far in high-order operation. This gives the operationEnterprises of electrolytic reduction methods for valence state adjustment of vanadium electrolytes bring about great cost pressures. In addition, the electrolytic reduction method using oxygen evolution reaction as auxiliary reaction is used for regulating the valence state of the vanadium electrolyte, and the problem that the anode liquid cannot be used for a long time exists.
Therefore, there is an urgent need to develop an electrolytic reduction method for valence adjustment of vanadium electrolyte that can be used for a long period of time without using iridium oxide anode and anolyte or anolyte, instead of the existing method.
(III) summary of the invention
The invention aims to provide an electrolytic reduction method for regulating valence state of vanadium electrolyte, which takes hydrogen oxidation reaction as anode reaction, and can not only avoid the use of expensive iridium oxide anode and avoid the use of anode liquid or ensure the long-term use of anode liquid, but also greatly reduce the electrolytic voltage, greatly improve the current efficiency of electrolytic reduction and solve the problems that the anode of the existing method is expensive and the anode liquid cannot be used for a long time.
The technical scheme adopted by the invention is as follows:
the invention provides an electrolytic reduction method for regulating valence state of vanadium electrolyte, which takes oxidation reaction of hydrogen as anode reaction, reduction reaction of vanadium ions as cathode reaction, and aqueous solution containing sulfuric acid as electrolyte for electrolysis, so that 5-valence or 4-valence vanadium in the electrolyte is reduced into 3-valence vanadium.
Further, the anodic reaction occurs on a gas diffusion electrode or a membrane electrode; the cathode reaction occurs on a carbon material including graphite flakes, carbon paper, carbon cloth, foam vitreous carbon, carbon felt, graphite felt, and the like, preferably graphite felt.
Further, the gas diffusion electrode consists of a gas diffusion layer and a catalytic layer, wherein the gas diffusion layer is made of a porous carbon material or a metal material, the carbon material is carbon paper, carbon cloth, graphite felt, carbon felt or carbon foam, and the metal material is titanium or silver; the catalytic layer is composed of a platinum carbon or palladium carbon catalyst and a binder, wherein the binder is polytetrafluoroethylene resin or Nafion resin or a mixture of the two.
Further, the Pt or Pd loading in the gas diffusion electrode is 0.1-0.5 mg/cm 2 。
Further, the membrane electrode consists of a gas diffusion layer, a catalytic layer and a cationic membrane, wherein the catalytic layer is positioned between the gas diffusion layer and the cationic membrane; the gas diffusion layer is made of porous carbon material or metal material, the carbon material is carbon paper, carbon cloth, graphite felt, carbon felt or carbon foam, and the metal material is titanium or silver; the catalytic layer consists of a platinum carbon or palladium carbon catalyst and a binder, wherein the binder is polytetrafluoroethylene resin or Nafion resin or a mixture of the two; the cationic membrane is a sulfonic acid type cationic membrane.
Further, the Pt or Pd loading in the membrane electrode is 0.1-0.5 mg/cm 2 。
Further, the electrolysis may be performed by a diaphragm (a and C in fig. 1) electrolysis method or a diaphragm-free (B and D in fig. 1) electrolysis method, preferably, a diaphragm-free method. When the membrane is used, the anolyte can be a vanadium ion-containing sulfuric acid aqueous solution (the concentration of vanadium ions is 0.01mmol/L-4 mol/L) or a vanadium ion-free sulfuric acid aqueous solution, and the anolyte is preferably a vanadium ion-free sulfuric acid aqueous solution, and the anolyte is repeatedly used for 1-30 times.
Further, the membrane adopted in the membrane electrolysis mode is a cationic membrane or a microporous membrane, preferably a Nafion-324 membrane. The electrolytic device in the diaphragm electrolysis mode is divided into a gas chamber, an anode chamber and a cathode chamber by an anode and a diaphragm in sequence, wherein the gas chamber is used for introducing hydrogen, the anode is arranged between the gas chamber and the anode chamber, the diaphragm is arranged between the anode chamber and the cathode chamber, and the cathode is arranged in the cathode chamber; an aqueous solution containing 1-5mol/L (preferably 2 mol/L) of sulfuric acid and 0-4mol/L (preferably 0-0.3 mmol/L) of vanadium ions is adopted as an anolyte; adopting an aqueous solution containing 1-5mol/L (preferably 2 mol/L) sulfuric acid and 1-5mol/L (preferably 2 mol/L) vanadyl sulfate (tetravalent vanadium) or 1-5mol/L (preferably 2 mol/L) vanadate (pentavalent vanadium) as a catholyte; at 0-80deg.C, cathode current density of 2.5-30A/dm 2 Anode current density 4.8-58A/dm 2 Lower electrolysis (preferably 40 ℃ C., cathode current density 20A/dm) 2 Anode current density 38A/dm 2 )。
Further, the electrolysis device in the diaphragm-free electrolysis mode is divided into a gas chamber and an electrolysis chamber by an anode, the anode is arranged between the gas chamber and the electrolysis chamber, a cathode is arranged in the electrolysis chamber, and the gas chamber is used for introducing hydrogen; an aqueous solution containing 1-5mol/L (preferably 2 mol/L) of sulfuric acid and 1-5mol/L (preferably 2 mol/L) of vanadyl sulfate (tetravalent vanadium) or 1-5mol/L (preferably 2 mol/L) of vanadic acid (pentavalent vanadium) is used as an electrolyte; at 0-80deg.C, cathode current density of 2.5-30A/dm 2 Anode current density 4.8-58A/dm 2 Lower electrolysis (preferably 40 ℃ C., cathode current density 20A/dm) 2 Anode current density 38A/dm 2 )。
Compared with the prior art, the invention has the beneficial effects that: (1) According to the electrolytic reduction method for regulating the valence state of the vanadium electrolyte, the hydrogen oxidation reaction is used as an anode reaction, preferably a membrane electrode or a gas diffusion electrode is used as an anode, and an iridium oxide anode is not used, so that the cost of noble metal on the anode is effectively reduced (reduced to 1/8-1/40); (2) When the diaphragm method is adopted, the anolyte can be used for a long time (30 times of internal electrolysis voltage stabilization), the current efficiency (8.9%) is obviously improved, and the electrolysis voltage is reduced by about 1.5V (compared with an iridium oxide anode). (3) The method can be carried out by adopting a diaphragm-free method, not only can avoid using a diaphragm and anolyte, but also can obviously improve the current efficiency (26.8-28.4%) and reduce the electrolysis energy consumption (more than 70%).
(IV) description of the drawings
FIG. 1 is a schematic diagram of a method for regulating valence state of a vanadium electrolyte, wherein the hydrogen oxidation reaction is an anode reaction; o represents a high valence vanadium ion, and R represents a low valence vanadium ion; a represents membrane electrode diaphragm electrolysis mode, B represents membrane electrode diaphragm-free electrolysis mode, C represents gas diffusion electrode diaphragm electrolysis mode, and D represents gas diffusion electrode diaphragm-free electrolysis mode.
FIG. 2 is a diagram of an electrolytic reduction apparatus in which the hydrogen oxidation reaction is an anodic reaction; a represents a diaphragm electrolyzer, and B represents a diaphragm-free electrolyzer.
FIG. 3, schematic view of a diaphragm-free plate and frame electrolyzer.
(fifth) detailed description of the invention
The invention will be further described with reference to the following specific examples, but the scope of the invention is not limited thereto: unless otherwise specified, all experimental aqueous solutions were prepared with deionized water.
In the following examples and comparative examples, the gas diffusion electrode (Pt loading was 0.1 to 0.5mg/cm 2 ) Membrane electrode (Pt loading is 0.1-0.5 mg/cm) 2 ) Gas diffusion electrode (Pd loading is 0.1-0.5 mg/cm) 2 ) And titanium-plated iridium oxide electrode (iridium content of 1 mg/cm) 2 ) Are purchased from the san francisco electrochemical instruments, inc.
The membrane electrode consists of a gas diffusion layer, a catalytic layer and a cationic membrane, wherein the catalytic layer is positioned between the gas diffusion layer and the cationic membrane. The carbon cloth is a gas diffusion layer, the catalytic layer is formed by mixing a platinum carbon catalyst and Nafion resin, and the cation membrane is a Nafion-117 membrane.
The gas diffusion electrode is composed of a gas diffusion layer and a catalytic layer. The carbon paper is a gas diffusion layer, and the catalytic layer is formed by mixing a platinum carbon catalyst, nafion resin and polytetrafluoroethylene resin.
The electrolytic reduction current efficiency (CE,%) performed is defined as:
wherein V is the volume (L) of the catholyte, C is the concentration change (mol/L) of the active substance in the catholyte, n is the number of electrons reduced by the active substance into a target product, I is the electrolysis current (A), and t is the electrolysis time (h).
Example 1 preparation of electrolyte containing vanadium 3 and vanadium 4 by gas diffusion electrode-diaphragm electrolysis
The diaphragm electrolytic cell adopting the structure shown in the figure 2A is divided into a gas chamber, an anode chamber and a cathode chamber by an anode and a diaphragm in sequence, wherein the anode is arranged between the gas chamber and the anode chamber, the diaphragm is arranged between the anode chamber and the cathode chamber, the cathode is arranged in the cathode chamber, and the gas chamber is used for introducing hydrogen. The gas diffusion electrode was the anode (area: 3.14 cm) 2 Pt loading was 0.5mg/cm 2 ) The graphite felt is the negativeElectrode (thickness 3mm, area 6 cm) 2 ) Nafion-324 membrane is used as diaphragm.
Taking an aqueous solution containing 2mol/L sulfuric acid as an anolyte (80 mL), and taking an aqueous solution containing 2mol/L sulfuric acid+2 mol/L vanadyl sulfate (tetravalent vanadium) as a catholyte (60 mL); in the electrolysis process, the flow rate of hydrogen is controlled to be 20mL/min. The temperature of the catholyte and the anolyte were controlled to 40℃and an electric current of 1200mA was applied for electrolysis (cathodic current density: 20A/dm) 2 The anode current density is: 38.2A/dm 2 ). After 1.5 hours of electrolysis, the electrolysis was stopped, the current efficiency was 89.3%, the conversion rate of vanadyl sulfate (tetravalent vanadium) in the catholyte was 50.1%, the yield of vanadium sulfate (trivalent vanadium) was 50.0%, the concentration of vanadium ions in the anolyte was 0.011mmol/L, and the average voltage was 4.1V (initial voltage was 3.9V, and the voltage at the end of electrolysis was 4.3V).
EXAMPLE 2 gas diffusion electrode-diaphragm electrolysis-preparation of electrolyte containing vanadium 3
A diaphragm cell of the construction shown in fig. 2a was employed. Taking an aqueous solution containing 2mol/L sulfuric acid and 2mol/L vanadyl sulfate (tetravalent vanadium) as an anolyte (80 mL), and taking an aqueous solution containing 2mol/L sulfuric acid and 2mol/L vanadyl sulfate (tetravalent vanadium) as a catholyte (60 mL); the gas diffusion electrode was the anode (area: 3.14 cm) 2 Pt loading was 0.3mg/cm 2 ) Graphite felt was the cathode (thickness 3mm, area: 6cm 2 ) Nafion-324 membrane is used as diaphragm. In the electrolysis process, the flow rate of hydrogen is controlled to be 20mL/min. The temperature of the catholyte and the anolyte were controlled to 40℃and an electric current of 1200mA was applied for electrolysis (cathodic current density: 20A/dm) 2 The anode current density is: 38.2A/dm 2 ). After 3 hours and 15 minutes of electrolysis, the electrolysis was stopped, the current efficiency was 82.0%, the conversion rate of vanadyl sulfate (tetravalent vanadium) in the catholyte was 99.7%, the yield of vanadium sulfate (trivalent vanadium) was 99.5%, and the average voltage was 4.3V (initial voltage was 3.9V, and voltage at the end of electrolysis was 4.5V).
Example 3 Membrane electrode-Membrane electrolysis-preparation of electrolyte containing vanadium 3 and vanadium 4
A diaphragm electrolytic cell with the structure shown in FIG. 2A takes an aqueous solution containing 2mol/L sulfuric acid and 4mol/L vanadyl sulfate (tetravalent vanadium) as an anolyte (80 mL) and contains 2mol/L sulfuric acidAn aqueous solution of +2mol/L vanadyl sulfate (tetravalent vanadium) as catholyte (60 mL); the membrane electrode was the anode (area: 3.14 cm) 2 Pt loading was 0.1mg/cm 2 ) The graphite flake is the cathode (thickness: 2mm, area is: 6cm 2 ) Nafion-324 membrane is used as diaphragm. In the electrolysis process, the flow rate of hydrogen is controlled to be 20mL/min. The temperature of the catholyte and the anolyte were controlled to 40℃and an electric current of 600mA was applied for electrolysis (cathodic current density: 10A/dm) 2 The anode current density is: 19.1A/dm 2 ). After 3 hours of electrolysis, the electrolysis was stopped, the current efficiency was 85.7%, the conversion rate of vanadyl sulfate (tetravalent vanadium) in the catholyte was 48.2%, the yield of vanadium sulfate (trivalent vanadium) was 48.1%, and the average voltage was 3.9V (initial voltage was 3.7V, and the voltage at the end of electrolysis was 4.2V).
EXAMPLE 4 gas diffusion electrode-diaphragm-less electrolysis-preparation of electrolyte containing vanadium 3 and vanadium 4
The diaphragm-free electrolytic cell with the structure shown in the figure 2B is divided into a gas chamber and an electrolytic chamber by an anode, the anode is arranged between the gas chamber and the electrolytic chamber, a cathode is arranged in the electrolytic chamber, and the gas chamber is used for introducing hydrogen. The gas diffusion electrode was the anode (area: 3.14 cm) 2 Pt loading was 0.5mg/cm 2 ) Graphite felt was the cathode (thickness 3mm, area: 6cm 2 )。
Taking an aqueous solution containing 2mol/L sulfuric acid and 2mol/L vanadyl sulfate (tetravalent vanadium) as electrolyte (60 mL); in the electrolysis process, the flow rate of hydrogen is controlled to be 20mL/min. The temperature of the electrolyte was controlled to 40℃and a current of 1200mA was applied to carry out electrolysis (cathode current density: 20A/dm) 2 The anode current density is: 38.2A/dm 2 . ). After 1 hour and 25 minutes of electrolysis, the electrolysis was stopped, the current efficiency was 94.6%, the conversion rate of vanadyl sulfate (tetravalent vanadium) in the catholyte was 50.1%, the yield of vanadium sulfate (trivalent vanadium) was 49.9%, and the average voltage was 3.6V (initial voltage was 3.4V, and voltage at the end of electrolysis was 3.8V).
Example 5 Membrane electrode-Membrane-free electrolysis-preparation of electrolyte containing vanadium 3 and vanadium 4
A diaphragm-free electrolytic cell having the structure shown in FIG. 2B was used to contain 2mol/L sulfuric acid+2 mol/L sulfuric acidThe aqueous solution of vanadyl (tetravalent vanadium) is electrolyte (60 mL); the membrane electrode was the anode (area: 3.14 cm) 2 Pt loading was 0.1mg/cm 2 ) The graphite flake is the cathode (thickness: 2mm, area is: 6cm 2 ). In the electrolysis process, the flow rate of hydrogen is controlled to be 20mL/min. The temperature of the electrolyte was controlled to 40℃and a current of 600mA was applied to carry out electrolysis (cathode current density: 10A/dm) 2 The anode current density is: 19.1A/dm 2 . ). After 3 hours of electrolysis, the electrolysis was stopped, the current efficiency was 85.7%, the conversion rate of vanadyl sulfate (tetravalent vanadium) in the catholyte was 48.1%, the yield of vanadium sulfate (trivalent vanadium) was 48.1%, and the average voltage was 3.5V (initial voltage was 3.3V, and the voltage at the end of electrolysis was 3.7V).
EXAMPLE 6 gas diffusion electrode-diaphragmless electrolysis-preparation of electrolyte containing vanadium 3
The diaphragm-free electrolytic cell with the structure shown in the diagram B in the diagram 2 takes an aqueous solution containing 2mol/L sulfuric acid and 2mol/L vanadyl sulfate (tetravalent vanadium) as electrolyte (60 mL); the gas diffusion electrode was the anode (area: 3.14 cm) 2 Pt loading was 0.5mg/cm 2 ) Graphite felt was the cathode (thickness 3mm, area: 6cm 2 ). In the electrolysis process, the flow rate of hydrogen is controlled to be 20mL/min. The temperature of the electrolyte was controlled to 40℃and a current of 1200mA was applied to carry out electrolysis (cathode current density: 20A/dm) 2 The anode current density is: 38.2A/dm 2 . ). After 3 hours of electrolysis, the electrolysis was stopped, the current efficiency was 88.9%, the conversion rate of vanadyl sulfate (tetravalent vanadium) in the electrolyte was 99.8%, the yield of vanadium sulfate (trivalent vanadium) was 99.5%, and the average voltage was 3.8V (initial voltage was 3.6V, and the voltage at the end of electrolysis was 4.0V).
Examples 7 to 15, catalyst type and Supported amount, electrolyte composition, effect of temperature, etc. on electrolytic reduction
The method of example 6 was used to carry out the electrolytic reaction under different catalyst types and loadings, electrolyte compositions and temperatures, and other operations were the same, and experimental conditions and results are shown in table 1.
TABLE 1 influence of catalyst type and loading, electrolyte composition, temperature, etc. on electrolytic reduction
Remarks: platinum carbon loadings of 0.5mg/cm 2 ； a The palladium loading on the electrode was 0.5mg/cm 2 ， b The palladium loading on the electrode was 0.1mg/cm 2 ， c The palladium loading on the electrode was 0.3mg/cm 2 。
Examples 16 to 19 influence of cathode materials on electrolytic reduction
In the case of the different cathode materials (area: 6cm in each case) by the method of example 6 2 ) The electrolysis reaction was carried out under the same conditions and the experimental conditions and results are shown in Table 2.
TABLE 2 Effect of cathode materials on electrolytic reduction
| Implementation sequence number | Cathode material | Yield of trivalent vanadium | Average voltage |
| 16 | Carbon paper | 91.8％ | 4.2V |
| 17 | Carbon cloth | 91.3％ | 4.2V |
| 18 | Foam glass carbon | 92.1％ | 3.9V |
| 19 | Carbon felt | 96.5％ | 3.9V |
Examples 20 to 22 influence of the current density on the electrolytic reduction
The electrolysis reaction was performed at different current densities by the method of example 6, and the other operations were the same, and experimental conditions and results are shown in table 3.
TABLE 3 influence of current density on electrolytic reduction
Examples 23 to 25, gas diffusion electrode-diaphragm electrolysis-preparation of electrolyte containing vanadium 3 and vanadium 4-repeated use of anolyte
The experiment was repeated using the method of example 1 without changing the anolyte and without changing the catholyte, and the other operations were the same, and the experimental conditions and results are shown in table 4.
TABLE 4 influence of not changing anolyte
a And (3) the concentration of vanadium ions in the anode liquid at the end of electrolysis. With repeated use of the anolyte, the concentration of vanadium ions is gradually increased, but the electrolysis voltage is not influenced.
EXAMPLE 26 gas diffusion electrode-diaphragm-less electrolysis-plate-frame cell-preparation of electrolyte containing vanadium 3 and vanadium 4
The plate-frame electrolytic cell adopting the structure shown in fig. 3 is divided into a gas chamber and an electrolytic chamber by an anode, the anode is arranged between the gas chamber and the electrolytic chamber, a cathode is arranged in the electrolytic chamber, and the gas chamber is used for introducing hydrogen.
Taking an aqueous solution containing 2mol/L sulfuric acid and 2mol/L vanadyl sulfate (tetravalent vanadium) as electrolyte (6L); the gas diffusion electrode was an anode (area: 60 cm) 2 Pt loading was 0.1mg/cm 2 ) Graphite felt was the cathode (thickness 3mm, area: 60cm 2 ). In the electrolysis process, the flow rate of hydrogen is controlled to be 200mL/min. The temperature of the electrolyte was controlled at 40℃and a current of 12A was applied to perform electrolysis (cathode current density: 20A/dm) 2 The anode current density is: 20A/dm 2 . ). After 15 hours of electrolysis, the electrolysis was stopped, the current efficiency was 89.3%, the conversion rate of vanadyl sulfate (tetravalent vanadium) in the catholyte was 50.1%, the yield of vanadium sulfate (trivalent vanadium) was 49.9%, the average voltage was 1.1V (initial voltage was 0.8V, and the voltage at the end of electrolysis was 1.4V).
EXAMPLE 27 gas diffusion electrode-diaphragm-free electrolysis-plate frame Electrolysis cell-preparation of electrolyte containing 3-valent vanadium and 4-valent vanadium Using 5-valent vanadium as raw materials
The plate-frame electrolytic cell adopting the structure shown in fig. 3 is divided into a gas chamber and an electrolytic chamber by an anode, the anode is arranged between the gas chamber and the electrolytic chamber, a cathode is arranged in the electrolytic chamber, and the gas chamber is used for introducing hydrogen.
Taking an aqueous solution containing 2mol/L sulfuric acid and 2mol/L vanadate (pentavalent vanadium) as electrolyte (2L); the gas diffusion electrode was an anode (area: 60 cm) 2 Pt loading was 0.3mg/cm 2 ) Graphite felt was the cathode (thickness 3mm, area: 60cm 2 ). In the electrolysis process, the flow rate of hydrogen is controlled to be 200mL/min. The temperature of the electrolyte was controlled at 40℃and a current of 12A was applied to perform electrolysis (cathode current density: 20A/dm) 2 The anode current density is: 20A/dm 2 . ). After 14 hours of electrolysis, the electrolysis was stopped, the current efficiency was 95.7%, the yield of vanadyl sulfate (tetravalent vanadium) in the catholyte was 50.0%, the yield of vanadium sulfate (trivalent vanadium) was 49.8%, and the average voltage was 0.8V (initial voltage was 0.2V, and voltage at the end of electrolysis was 1.4V).
Comparative example 1 Iridium oxide anode-diaphragm electrolysis
The diaphragm electrolytic cell with the structure shown in the figure 2A is adopted, wherein the aqueous solution containing 2mol/L sulfuric acid is taken as anode solution (80 mL), and the aqueous solution containing 2mol/L sulfuric acid and 2mol/L vanadyl sulfate (tetravalent vanadium) is taken as cathode solution (60 mL); the titanium-plated iridium oxide electrode is an anode (area: 3.14 cm) 2 ) Graphite felt was the cathode (thickness 3mm, area: 6cm 2 ) Nafion-324 membrane is used as diaphragm. In the electrolysis process, the flow rate of hydrogen is controlled to be 0mL/min. The temperature of the catholyte and the anolyte were controlled to 40℃and an electric current of 1200mA was applied for electrolysis (cathodic current density: 20A/dm) 2 The anode current density is: 38.2A/dm 2 ). After 1.5 hours of electrolysis, the electrolysis was stopped, the current efficiency was 80.4%, the conversion rate of vanadyl sulfate (tetravalent vanadium) in the catholyte was 45.1%, the yield of vanadium sulfate (trivalent vanadium) was 45.0%, the concentration of vanadium ions in the anolyte was 0.12mmol/L, the average voltage was 4.1+1.5V (initial voltage was 3.9+1.5V, and the voltage at the end of electrolysis was 4.3+1.5V).
Comparative example 1, the average voltage during electrolysis increased by 1.5V; the consumption of noble metal is increased to 2 times of the original consumption, and the price is increased to about 8 times of the original consumption; the current efficiency was reduced by 8.9%.
Comparative examples 2 to 4, iridium oxide anode-diaphragm electrolysis-repeated use of anolyte
The comparative example 1 method was used to carry out repeated experiments without changing the anolyte and changing the catholyte, and the other operations were the same, and the experimental conditions and results are shown in table 5.
TABLE 5 influence of not changing anolyte
a And (3) the concentration of vanadium ions in the anode liquid at the end of electrolysis. With repeated use of the anolyte, the concentration of vanadium ions therein was gradually increased, and in comparative examples 23 to 25, the average electrolytic voltage was unstable and gradually increased.
Comparative example 5 Iridium oxide Anode-diaphragm-less electrolysis
The diaphragm-free electrolytic cell with the structure shown in the diagram B in the diagram 2 takes an aqueous solution containing 2mol/L sulfuric acid and 2mol/L vanadyl sulfate (tetravalent vanadium) as electrolyte (60 mL); the titanium-plated iridium oxide electrode is an anode (area: 3.14 cm) 2 ) Graphite felt was the cathode (thickness 3mm, area: 6cm 2 ). In the electrolysis process, the flow rate of hydrogen is controlled to be 0mL/min. The temperature of the electrolyte was controlled to 40℃and a current of 1200mA was applied to carry out electrolysis (cathode current density: 20A/dm) 2 The anode current density is: 38.2A/dm 2 . ). After electrolysis for 1 hour and 25 minutes, the electrolysis was stopped, the current efficiency was 66.2%, the conversion rate of vanadyl sulfate (tetravalent vanadium) in the catholyte was 35.1%, the yield of vanadium sulfate (trivalent vanadium) was 35.0%, the average voltage was 3.6+1.5v (initial voltage was 3.4+1.5v, and the voltage at the end of electrolysis was 3.8+1.5v).
Comparative example 4, the average voltage during electrolysis increased by 1.5V; the consumption of noble metal is increased to 2 times of the original consumption, and the price is increased to about 8 times of the original consumption; the current efficiency was reduced by 28.4%.
Comparative example 6 Iridium oxide anode-diaphram-less electrolysis-plate-frame electrolyzer
The plate-frame electrolytic tank with the structure shown in the figure 3 takes an aqueous solution containing 2mol/L sulfuric acid and 2mol/L vanadyl sulfate (tetravalent vanadium) as electrolyte (6L); the titanium-plated iridium oxide electrode is an anode (area: 60 cm) 2 ) Graphite felt was the cathode (thickness 3mm, area: 60cm 2 ). In the electrolysis process, the flow rate of hydrogen is controlled to be 0mL/min. The temperature of the electrolyte was controlled at 40℃and a current of 12A was applied to perform electrolysis (cathode current density: 20A/dm) 2 The anode current density is: 20A/dm 2 . ). After 15 hours of electrolysis, the electrolysis was stopped, the current efficiency was 62.5%, the conversion rate of vanadyl sulfate (tetravalent vanadium) in the catholyte was 35.2%, the yield of vanadium sulfate (trivalent vanadium) was 35.1%, and the average voltage was 2.6V (initial voltage was 2.3V, and the voltage at the end of electrolysis was 2.9V).
Comparative example 26, the average voltage during electrolysis increased by 1.5V; the consumption of noble metal is increased to 10 times of the original consumption, and the price is increased to about 40 times of the original consumption; the current efficiency is reduced by 26.8 percent, and the electrolysis energy consumption is increased to 3.4 times.
Claims (8)
1. The electrolytic reduction method for regulating the valence state of the vanadium electrolyte is characterized in that the method takes oxidation reaction of hydrogen as anode reaction, reduction reaction of vanadium ions as cathode reaction, and sulfuric acid aqueous solution as electrolyte for electrolysis, so that 5-valence or 4-valence vanadium in the electrolyte is reduced to 3-valence vanadium.
2. The method of claim 1, wherein the anodic reaction occurs on a gas diffusion electrode or a membrane electrode; the cathodic reaction occurs on the carbonaceous material.
3. The method of claim 2, wherein the carbon material comprises graphite sheet, carbon paper, carbon cloth, foam vitreous carbon, carbon felt, graphite felt.
4. The method of claim 2, wherein the gas diffusion electrode is composed of a gas diffusion layer and a catalytic layer, the gas diffusion layer is porous carbon or a metal material, the carbon material is carbon paper, carbon cloth, graphite felt, carbon felt or carbon foam, and the metal material is titanium or silver; the catalytic layer consists of a platinum carbon or palladium carbon catalyst and a binder, wherein the binder is polytetrafluoroethylene resin or Nafion resin or a mixture of the two; the platinum or palladium loading in the gas diffusion electrode is 0.1-0.5 mg/cm 2 。
5. The method of claim 2, wherein the membrane electrode consists of a gas diffusion layer, a catalytic layer, and a cationic membrane, the catalytic layer being located between the gas diffusion layer and the cationic membrane; the gas diffusion layer is made of porous carbon or metal material, the carbon material is carbon paper, carbon cloth, graphite felt, carbon felt or carbon foam, and the metal material is titanium or silver; the catalytic layer consists of a platinum carbon or palladium carbon catalyst and a binder, wherein the binder is polytetrafluoroethylene resin or Nafion resin or a mixture of the two; the cation membrane is a sulfonic acid type cation membrane; the platinum or palladium loading in the membrane electrode is 0.1-0.5 mg/cm 2 。
6. The method of claim 1, wherein the electrolysis is performed by diaphragm electrolysis or no diaphragm electrolysis, and the diaphragm used by diaphragm electrolysis is a cationic membrane or a microporous membrane.
7. The method according to claim 6, wherein the electrolytic device of the diaphragm electrolysis mode is divided into a gas chamber, an anode chamber and a cathode chamber by an anode and a diaphragm in sequence, the gas chamber is used for introducing hydrogen, and a cathode is arranged in the cathode chamber; adopting an aqueous solution containing 1-5mol/L sulfuric acid and 0-4mol/L vanadium ions as anode liquid; adopting an aqueous solution containing 1-5mol/L sulfuric acid+1-5 mol/L vanadyl sulfate or 1-5mol/L vanadate as a catholyte; at 0-80deg.C, cathode current density of 2.5-30A/dm 2 Anode current density 4.8-58A/dm 2 And (5) electrolysis.
8. The method according to claim 6, wherein the electrolysis device of the diaphragm-free electrolysis mode is divided into a gas chamber and an electrolysis chamber by an anode, the anode is arranged between the gas chamber and the electrolysis chamber, a cathode is arranged in the electrolysis chamber, and the gas chamber is used for introducing hydrogen; adopting an aqueous solution containing 1-5mol/L sulfuric acid+1-5 mol/L vanadyl sulfate or 1-5mol/L vanadate as an electrolyte; at 0-80deg.C, cathode current density of 2.5-30A/dm 2 Anode current density 4.8-58A/dm 2 And (5) electrolysis.
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