CN108695520A

CN108695520A - α-MnO2Oxygen reduction catalyst and preparation method thereof and metal-air battery

Info

Publication number: CN108695520A
Application number: CN201810497037.8A
Authority: CN
Inventors: 刘跃军; 李福枝; 石璞
Original assignee: Xiamen University of Technology
Current assignee: Xiamen University of Technology
Priority date: 2018-05-22
Filing date: 2018-05-22
Publication date: 2018-10-23

Abstract

A kind of α-MnO₂The preparation method of oxygen reduction catalyst, includes the following steps:S1 is 1 according to molar ratio:1:1 Manganous sulfate monohydrate, alkali metal sulfates and potassium peroxydisulfate, is dissolved in deionized water and forms uniform aqueous solution;Hydrochloric acid solution formation mixed liquor is added, wherein the molar ratio of HCl and Manganous sulfate monohydrate is 4~6 in the hydrochloric acid solution in S2 in the aqueous solution:1;The mixed liquor is heated to 120 DEG C~160 DEG C and reacted 0.1~15 hour by S3;And S4, after cooled to room temperature, obtained product is filtered by vacuum, and fully dry, final obtain contains Mn³⁺/Mn⁴⁺α-the MnO of ion₂.The present invention also provides a kind of α-MnO obtained by the above method₂Oxygen reduction catalyst and metal-air battery.

Description

α-MnO2Oxygen reduction catalyst and preparation method thereof and metal-air battery

Technical field

The present invention relates to a kind of α-MnO₂Oxygen reduction catalyst and preparation method thereof and containing the catalyst metal-air electricity Pond.

Background technology

In fast development cleaning and regenerative resource conversion/storing technology (including fuel cell, metal-air batteries) side Face needs efficient hydrogen reduction (ORR) elctro-catalyst.It is well known that noble metal platinum and its alloy are considered as most effective quotient Industry ORR catalyst, however, their high cost and scarcity have become the major obstacle of large-scale commercial applications application.

In recent years, various non-noble metallic materials have been developed that as ORR catalyst, such as various carbon materials, polymer and mistake Cross metal oxide.Wherein, manganese dioxide is received more and more attention because its abundance is high, at low cost, catalytic activity is high.According to Report, in the manganese dioxide of five kinds of different crystal forms, α-MnO₂Show optimal hydrogen reduction electrocatalysis characteristic.

Scientists are found, in α-MnO₂In suitably introduce Mn³⁺, change wherein Mn⁴⁺With Mn³⁺Ratio, can be right to its Oxygen reduction reaction catalytic performance has an impact.This is because Mn³⁺σ * antibonding orbitals on be filled with an electronics and activity increases It is caused.Also the study found that a certain extent, α-MnO₂Electro catalytic activity with Mn³⁺/Mn⁴⁺Ratio increases and increases.

However, failing to solve regulation and control Mn in the prior art³⁺/Mn⁴⁺The problem of ratio, also without any about Mn³⁺/Mn⁴⁺Than The associated regulatory method of value.

Invention content

In view of this, Mn can be solved it is necessory to provide one kind³⁺/Mn⁴⁺α-the MnO of ratio regulation and control₂Preparation method.

A kind of α-MnO₂Preparation method, include the following steps:

S1 is 1 according to molar ratio:1:1 Manganous sulfate monohydrate, alkali metal sulfates and potassium peroxydisulfate, be dissolved in from Uniform aqueous solution is formed in sub- water;

Hydrochloric acid solution formation mixed liquor is added, wherein HCl and a water in the hydrochloric acid solution in S2 in the aqueous solution The molar ratio for closing manganese sulfate is 4~6:1;

The mixed liquor is heated to 120 DEG C~160 DEG C and reacted 0.1~15 hour by S3;And

After cooled to room temperature, obtained product is filtered by vacuum by S4, and fully dry, is finally contained There is Mn³⁺/Mn⁴⁺α-the MnO of ion₂。

As further improved, in step sl, the alkali metal sulfates include potassium sulfate, sodium sulphate or its mixing Object.

As further improved, in step s3, the mixed liquor is heated to 145 DEG C~155 DEG C reactions 0.1~1 Hour.

As further improved, in step s3, the mixed liquor be heated to 150 DEG C and is reacted 0.5 hour.

As further improved, in step s 4, described the step of obtained product is filtered by vacuum, includes: Obtained product is filtered by vacuum in sand core Suction filtration device, wherein used filter membrane is that aperture is 0.15 μm Aqueous fiber filter membrane.

As further improved, in step s 4, the fully dry step includes:It is deposited in what is be obtained by filtration It is fully dry at 80 DEG C in air dry oven.

As further improved, in step sl, the Manganous sulfate monohydrate is a concentration of in the aqueous solution 0.125mol/L。

As further improved, in step s 2, the hydrochloric acid solution is the hydrochloric acid solution of 37wt%.

As further improved, in step s 2, the molar ratio of HCl and Manganous sulfate monohydrate is in the hydrochloric acid solution 4.8:1。

The present invention also provides a kind of α-MnO₂Oxygen reduction catalyst, the α-MnO₂Oxygen reduction catalyst passes through above-mentioned side Method is made.

The present invention furthermore provides a kind of metal-air battery, includes such as above-mentioned α-MnO₂Oxygen reduction catalyst.

A kind of α-MnO provided by the invention₂Oxygen reduction catalyst and preparation method thereof and metal-air containing the catalyst Battery has the following advantages:Persulfuric acid is utilized using the mild water-heat process that can be mass-produced using inexpensive raw material The redox reaction of potassium and manganese sulfate in acid condition is preparing α-MnO₂While in α-MnO₂Manganic ion is introduced, And by changing reaction temperature and reaction time to its Mn³⁺/Mn⁴⁺Ratio is regulated and controled.

Description of the drawings

Fig. 1 is the X-ray diffractogram of the standard card of three kinds of samples provided in an embodiment of the present invention.

Fig. 2 is the Mn 2p XPS figures and Mn of three kinds of samples provided in an embodiment of the present invention³⁺/Mn⁴⁺Ratio figure.

Fig. 3 is that hydrogen reduction (ORR) catalytic activity of three kinds of samples provided in an embodiment of the present invention compares.

Fig. 4 is hydrogen reduction (ORR) catalytic activity ratio of a kind of sample and business 20%Pt/C provided in an embodiment of the present invention Compared with.

Fig. 5 is that a kind of sample and business 20%Pt/C provided in an embodiment of the present invention are applied in aluminium-air cell respectively Polarization curve (a) and constant current discharge curve (b).

Specific implementation mode

Below in conjunction with drawings and embodiments to a kind of α-MnO of the present invention₂Preparation method make specific introduce.

α-MnO₂Preparation method:

Embodiment 1:Weigh the Manganous sulfate monohydrate (MnSO of 1.70g (10 mMs)₄·H₂O), 0.145g (10 mMs) Sodium sulphate (Na₂SO₄) (or 1.74g potassium sulfates (10 mMs)), the potassium peroxydisulfate (K of 2.71g (10 mMs)₂S₂O₈), It is dissolved in 80mL deionized waters, magnetic agitation at least 15 minutes is to form uniform aqueous solution.Then 4mL 37% is added dropwise Hydrochloric acid (HCl) solution, stirring make it be uniformly mixed for 5 minutes.The stainless steel casing that this homogeneous mixture solotion is transferred to 100mL gathers In the hydrothermal reaction kettle of tetrafluoroethene liner.This hydrothermal reaction kettle is placed in air dry oven, 120 DEG C and herein temperature are heated to The lower reaction of degree 12 hours.After cooled to room temperature, obtained reaction mixture is subjected to vacuum in sand core Suction filtration device It filters.Used filter membrane is the aqueous fiber filter membrane that aperture is 0.15 μm.It is deposited in what is be obtained by filtration in air dry oven Fully dry at 80 DEG C, obtained product is denoted as is denoted as MnO respectively₂-SM120-12。

Embodiment 2:Weigh the Manganous sulfate monohydrate (MnSO of 1.70g (10 mMs)₄·H₂O), 0.145g (10 mMs) Sodium sulphate (Na₂SO₄) (or 1.74g potassium sulfates (10 mMs)), the potassium peroxydisulfate (K of 2.71g (10 mMs)₂S₂O₈), It is dissolved in 80mL deionized waters, magnetic agitation at least 15 minutes is to form uniform aqueous solution.Then 4mL 37% is added dropwise Hydrochloric acid (HCl) solution, stirring make it be uniformly mixed for 5 minutes.The stainless steel casing that this homogeneous mixture solotion is transferred to 100mL gathers In the hydrothermal reaction kettle of tetrafluoroethene liner.This hydrothermal reaction kettle is placed in air dry oven, 150 DEG C is heated to and reacts 30 points Clock.After cooled to room temperature, obtained reaction mixture is filtered by vacuum in sand core Suction filtration device.It is used Filter membrane is the aqueous fiber filter membrane that aperture is 0.15 μm.Being deposited in air dry oven of being obtained by filtration is fully dry at 80 DEG C Dry, obtained product is denoted as is denoted as MnO respectively₂-SM150-0.5。

Embodiment 3:Weigh the Manganous sulfate monohydrate (MnSO of 1.70g (10 mMs)₄·H₂O), 0.145g (10 mMs) Sodium sulphate (Na₂SO₄) (or 1.74g potassium sulfates (10 mMs)), the potassium peroxydisulfate (K of 2.71g (10 mMs)₂S₂O₈), It is dissolved in 80mL deionized waters, magnetic agitation at least 15 minutes is to form uniform aqueous solution.Then 4mL 37% is added dropwise Hydrochloric acid (HCl) solution, stirring make it be uniformly mixed for 5 minutes.The stainless steel casing that this homogeneous mixture solotion is transferred to 100mL gathers In the hydrothermal reaction kettle of tetrafluoroethene liner.This hydrothermal reaction kettle is placed in air dry oven, 120 DEG C and herein temperature are heated to The lower reaction of degree 30 minutes.After cooled to room temperature, obtained reaction mixture is subjected to vacuum in sand core Suction filtration device It filters.Used filter membrane is the aqueous fiber filter membrane that aperture is 0.15 μm.It is deposited in what is be obtained by filtration in air dry oven Fully dry at 80 DEG C, obtained product is denoted as is denoted as MnO respectively₂-SM120-0.5。

The preparation method of N-KB:0.2g Ketjen blacks conductive carbon powder (KB) and 1.2g melamines accurately are weighed, is mixed Object is dissolved in jointly in 80mL deionized waters, ultrasonic disperse at least 30 minutes, so as to the Ketjen black and melamine being uniformly mixed The suspension of amine.Then, this suspension is transferred to the hydrothermal reaction kettle of the stainless steel casing polytetrafluoroethylliner liner of 100mL In.This hydrothermal reaction kettle is placed in air dry oven again, be heated to 120 DEG C and is reacted 24 hours at this temperature.Naturally cold But to after room temperature, obtained reaction mixture is filtered by vacuum using sand core Suction filtration device.It is used on sand core funnel Filter membrane is the aqueous fiber filter membrane that aperture is 0.15 μm.Drying at 80 DEG C is deposited in air dry oven by what vacuum filter obtained Overnight to abundant dry.Substance after drying is ground at least 10 minutes in agate mortar, block will be formed in drying process The substance of shape wears into careful consistent powder-like substance uniform in size.This powder is transferred in the porcelain boat of 30 × 60mm, on Face covers a piece of an equal amount of porcelain boat again, makes it up and down to just getting togather.It is close that porcelain boat will be got togather with red copper foil above and below this two panels It wraps, outside is wound with copper wire bind again.Then the porcelain boat that this is handled well is put into tube furnace, is first pumped into tube furnace very Sky, then it is slowly introducing argon gas, and under the protection of argon gas stream, with 5 DEG C of min^-1Heating speed be heated to 650 DEG C from room temperature, And it is kept for 2 hours at this temperature.Finally, section's qin of N doping is obtained after cooled to room temperature under the protection in argon gas stream Black conductive carbon powder, is denoted as N-KB.

The preparation method of three-electrode system Oxygen Cathode Catalyst working electrode

Accurately weigh 2mg MnO₂, 4mg N-KB, be added 950 μ L absolute ethyl alcohols in, ultrasonic disperse 20 minutes, be added 50 μ L The Nafion solution of 5wt%, it is ultrasonic again to obtain within 20 minutes finely dispersed catalyst liquid.8 μ L of this liquid are taken, glass is slowly dropped to In carbon disk electrode, just it is completely covered the surface of glass-carbon electrode to form MnO₂/ N-KB composite catalysts, catalyst loadings For 0.0815mgcm^-2.For the ease of comparing, business platinum carbon (20wt%Pt/C Johnson Matthey) working electrode is also such as Prepared by the above method, dosage is 6mg Pt/C, no longer additionally adds N-KB.

2, in full battery oxygen cathode (anode) preparation method

The battery net capacity size is 50 × 32 × 50mm, wherein containing there are one a diameter of 10mm circular holes, in order to air Penetrate.Wherein cathode is the rectangle aluminium alloy plate of 2 × 8cm of 2~3mm thickness.The just extremely air permeable waterproof containing catalyst Air electrode.Electrolyte uses 6molL^-1KOH strong base solutions.A certain amount of corrosion inhibitor is wherein added, such as 0.01mol·L^-1Na₂SnO₃, 0.0075molL^-1ZnO and 0.0005molL^-1In(OH)₃。

The production method of air electrode is as follows.It takes big a certain amount of catalyst (40~60mg) in agate mortar, is added Absolute ethyl alcohol is uniformly mixed.60wt% polytetrafluoroethylene (PTFE) (PTFE) aqueous solution about 50mg is added, shape is uniformly mixed Pulp object.It stirs with keeping, roll until forming the goo that can be kneaded.In on the clean glass plate of drying, It is rolled with glass bar molded, is allowed to form the rectangular Catalyst flakes of 2 × 2cm sizes.Finally, take one piece of 2 clean × 8cm big Catalyst flakes and waterproof and breathable carbon cloth are kept 20~30s to be pressed in nickel foam by small nickel foam under about 15MPa pressure Two sides, be then dried overnight at 60 DEG C, obtain air electrode.For the ease of comparing, 20wt%Pt/C (Johnson are used Matthey also described above prepared by method for air electrode).The constant current discharge performance and full battery polarization curve of full battery are adopted It is tested with the new Weir battery test system in Shenzhen (Neware Battery Testing System).

Test and analysis:

Fig. 1 is MnO₂- SM120-12, MnO₂- SM150-0.5, MnO₂- SM120-0.5 and α-MnO₂The X of standard card is penetrated Ray diffraction diagram, it is obvious that MnO₂- SM120-12, MnO₂- SM150-0.5, MnO₂Three kinds of products of-SM120-0.5 are α-MnO₂。 This shows using the redox reaction between potassium peroxydisulfate and manganese sulfate, and α-MnO can successfully be made₂。

Fig. 2 is the Determination of Different Valence States figure of manganese element in made catalyst.As seen from the figure, three kinds of catalyst MnO₂- SM120-12, MnO₂- SM150-0.5 and MnO₂The photoelectron spectroscopy figure of the manganese element of-SM120-0.5 can be fitted to four peaks, respectively position In 654.80eV, 653.80eV, 643.25eV, 642.30eV, correspond to Mn⁴⁺(2p_1/2), Mn³⁺(2p_1/2), Mn⁴⁺(2p_3/2), Mn³⁺(2p_3/2)。

The peak area ratio at four peaks being fitted according to fig. 2, can extrapolate sample MnO₂- SM120-12, MnO₂- SM150-0.5, MnO₂The Mn of-SM120-0.5³⁺/Mn⁴⁺Ratio size, the results are shown in Table 1.By table as it can be seen that MnO₂- SM120-12, MnO₂- SM150-0.5, MnO₂The Mn of-SM120-0.5³⁺/Mn⁴⁺Ratio be respectively 0.813,0.965,0.512.This means that MnO₂- SM150-0.5, which contains, compares MnO₂- SM120-0.5 and MnO₂- SM120-12 wants high Manganic ion.This shows over cure Redox reaction between sour potassium and manganese sulfate can regulate and control Mn in product by changing reaction temperature and reaction time³⁺/ Mn⁴⁺Ratio size.Specifically, in relatively high reaction temperature and product obtained in the shorter reaction time, than in phase To product obtained compared with low reaction temperatures and in the reaction time, contain more Manganic ions.

Table 1 is MnO₂- SM120-12, MnO₂- SM150-0.5, MnO₂The Mn of-SM120-0.5³⁺/Mn⁴⁺Ratio size

Researcher unanimously thinks, Mn³⁺/Mn⁴⁺Higher α-the MnO of ratio₂, ORR catalytic activity is better than Mn³⁺/Mn⁴⁺Than It is worth lower α-MnO₂.In order to which this viewpoint is better described, both prepared catalyst are pressed with N-KB in this method It is 1 according to mass ratio:(it is specially 2mg after 2 ratio mixing:ORR catalytic performances 4mg) are tested, and as a result see Fig. 3 respectively.

Fig. 3 is catalyst MnO₂- SM120-12, MnO₂- SM150-0.5, MnO₂The hydrogen reduction (ORR) of-SM120-0.5 LSV curve graphs.As it can be seen that MnO₂- SM150-0.5 shows to compare MnO₂- SM120-12 and MnO₂The better ORR of-SM120-0.5 are urged Change activity, has the half wave potential (~0.77V vs.RHE) corrected and bigger with stable limiting current density (about 6.2mA cm^-2)。

Fig. 3 catalyst MnO₂- SM120-12, MnO₂- SM150-0.5, MnO₂The hydrogen reduction (ORR) of-SM120-0.5 is catalyzed Expression activitiy (test condition:O₂The 0.1M KOH solutions of saturation, rotating speed 1600rpm, sweep speed 10mVs^-1)

Fig. 4 is catalyst MnO₂The LSV of the hydrogen reduction (ORR) of-SM150-0.5 and business 20%Pt/C (J.M. brands) is bent Line chart (test condition:O₂The 0.1M KOH solutions of saturation, rotating speed 1600rpm, sweep speed 10mVs^-1).Although as it can be seen that urging Agent MnO₂The half wave potential (~0.77V vs.RHE) of-SM150-0.5 is not so good as Pt/C (~0.82V vs.RHE), but the limit Current density (about 6.1mAcm^-2) (about 5.2mAcm than Pt/C^-2) big.Generally, MnO₂-SM150-0.5 ORR catalytic performances can compare favourably with Pt/C.

Fig. 5 is catalyst MnO₂- SM150-0.5 and business 20%Pt/C (J.M. brands) is cloudy as aluminium-air cell oxygen Cell polarization curves (a) when electrode catalyst and constant current discharge curve (b).From Fig. 5 (a) as it can be seen that when discharge current density is small In 150mAcm^-2When, use MnO₂Battery of the cell output voltage of-SM150-0.5 catalyst than using Pt/C catalyst Output voltage wants high.It is 150mAcm in discharge current density^-2~180mAcm^-2When, use MnO₂- SM150-0.5 is catalyzed The cell output voltage of agent is almost equal with the output voltage of the battery of Pt/C catalyst is used.From Fig. 5 (b) as it can be seen that in permanent electricity Stream power-discharging density is 50mAcm^-2After lower electric discharge 10 hours, MnO is used₂The battery of-SM150-0.5 catalyst reaches voltage The discharge voltage plateau of 1.23V is higher than the voltage platform (~1.19V) of Pt/C catalyst.

Generally speaking, catalyst MnO₂- SM150-0.5 has than MnO₂- SM120-12 and MnO₂- SM120-0.5 is good ORR catalytic activity.This is primarily due to MnO₂- 150-0.5 contains highest Mn³⁺/Mn⁴⁺The reason of ratio, because of Mn³⁺It is anti- It is filled with a single electron on bond orbital σ * and its activity is caused to greatly enhance.Catalyst MnO₂The ORR of-SM150-0.5 is catalyzed Activity can compare favourably with the catalytic activity of business J.M. platinum carbons.As catalyst MnO₂- SM150-0.5 is applied to aluminium-air cell When middle conduct cathodic oxygen reduction catalyst, battery polarization performance and constant current discharge voltage are used as aluminium-than business 20%Pt/C It to be got well when air battery cathode oxygen reduction catalyst.

In addition, those skilled in the art can also do other variations in spirit of that invention, certainly, these are smart according to the present invention The variation that god is done should all be included in the interior of scope of the present invention.

Claims

1. a kind of α-MnO₂The preparation method of oxygen reduction catalyst, includes the following steps:

S1 is 1 according to molar ratio:1:1 Manganous sulfate monohydrate, alkali metal sulfates and potassium peroxydisulfate, is dissolved in deionized water It is middle to form uniform aqueous solution;

Hydrochloric acid solution formation mixed liquor is added in S2 in the aqueous solution, wherein the hydrations of HCl and one sulphur in the hydrochloric acid solution The molar ratio of sour manganese is 4~6:1;

After cooled to room temperature, obtained product is filtered by vacuum by S4, and fully dry, and final obtain contains Mn³ ⁺/Mn⁴⁺α-the MnO of ion₂。

2. preparation method as described in claim 1, which is characterized in that in step sl, the alkali metal sulfates include sulphur Or mixtures thereof sour potassium, sodium sulphate.

3. preparation method as described in claim 1, which is characterized in that in step s3, the mixed liquor is heated to 145 DEG C ~155 DEG C are reacted 0.1~1 hour.

4. preparation method as described in claim 1, which is characterized in that in step s3, the mixed liquor is heated to 150 DEG C Reaction 0.5 hour.

5. preparation method as described in claim 1, which is characterized in that in step s 4, described to carry out obtained product The step of vacuum filtration includes:Obtained product is filtered by vacuum in sand core Suction filtration device, wherein used filter Film is the aqueous fiber filter membrane that aperture is 0.15 μm.

6. preparation method as described in claim 1, which is characterized in that in step s 4, the fully dry step includes: Being deposited in air dry oven at 80 DEG C of being obtained by filtration is fully dry.

7. preparation method as described in claim 1, which is characterized in that in step sl, the Manganous sulfate monohydrate is described A concentration of 0.125mol/L in aqueous solution.

8. preparation method as claimed in claim 7, which is characterized in that in step s 2, the hydrochloric acid solution is 37wt%'s Hydrochloric acid solution.

9. a kind of α-MnO₂Oxygen reduction catalyst, which is characterized in that the α-MnO₂Oxygen reduction catalyst is according to claim 1- 8 any one of them methods are made.

10. a kind of metal-air battery, it is characterised in that:Including α-MnO as claimed in claim 9₂Oxygen reduction catalyst.