CN101225526A - Nanocrystalline manganese bioxide coated anode and method for making same - Google Patents

Abstract

The invention relates to a nanocrystalline manganese dioxide anode and the preparation method, in particular to nanocrystalline manganese dioxide anode and the preparation method for sodium hypochlorite generators. The anode material comprises a valve metal matrix, an interlayer for oxidation resisting protection and a manganese dioxide catalyst layer. The metal matrix is treated through sandblasting and acid embossing; the interlayer is coated with corresponding organic or inorganic salt and pyrolyzed at 300 to 600 DEG C for 5 to 15 minutes; the outer layer of manganese dioxide coating can be obtained through pyrolytic process or electrodeposition process; the total amount of the coated catalyst layer is 10 to 20gm<-2>. The nanocrystalline manganese dioxide catalyst layer prepared using anode electrodeposition process has nano-fiber-like tissue, the average diameter is 9nm, and the length is 100nm; the nanocrystalline manganese dioxide catalyst layer prepared using pyrolytic process has granular nanometer-sized structure, and the diameter is 30 to 50nm. The nanocrystalline manganese dioxide anode has the advantages of strong antioxidant capacity, good electrocatalytic performance, ability to substitute noble metal oxide anode, and greatly reduced cost.

Description

Nanocrystalline manganese bioxide coated anode and preparation method thereof

Technical field

The present invention relates to anode coating material that a kind of electrolysis uses and preparation method thereof, relate to manganese bioxide coated anode material that the hypochlorite generator uses and preparation method thereof in particular.

Background technology

The chlorine bleach liquor is the strong oxidizer that a kind of non-natural exists.Its fungicidal effectiveness is stronger than chlorine, belong to real efficient, wide spectrum, safety the brute force sterilization, medicament kills the virus.Clorox stable poor, the chlorine bleach liquor of sterilization usefulness is many to produce in the mode of producer on-site preparation.Employing diaphragm-free electrolysis concentration is the chlorine bleach liquor that the salt solution of 3%-5% can generate a small amount of lower concentration.The low concentration of salt water electrolysis requires anode material that separating out of chlorine had good catalytic action, good endurance, and have the ability that oxygen is separated out that suppresses, therefore, general both at home and abroad employing metal oxide containing precious metals electrode is a coated titanium electrode, generally is referred to as the dimensional stabilizing electrode.It is with metal titanium as electrode matrix, be the activated coating of main ingredient with the platinum group metal oxide in surface applied.

Along with the fast development of industry, increasing at present to the demand of extremely rare precious metal, cause worldwide noble metal amount fewer and feweri, price rapidly goes up, and has improved industrial cost greatly.In recent years, the scientific research personnel of various countries is at positive coating of metal oxides cheaply, to substitute the precious metal oxide coating anode of current use.

It is generally acknowledged, the oxidation of the inefficacy of coated anode and titanium matrix and the dissolving of active catalytic layer consume relevant, and the clear 60-22704 of Japanese Patent discloses the mixture that the oxide compound of the mixture of titanium dioxide, tindioxide and tantalum pentoxide and niobium oxides forms and used as the middle layer.Manganse Dioxide is mainly used in the positive pole and the ultracapacitor of zinc-manganse dioxide dry cell, is not suitable for being applied in the electrolytic anode material because its higher resistivity be it is generally acknowledged.

Summary of the invention

The object of the present invention is to provide a kind of nanocrystalline manganese bioxide coated anode and preparation thereof; adopt the method in the middle layer of adding protectiveness; and utilize Manganse Dioxide high corrosion-resistant and oxidation resistant characteristics in acid-basicity solution; utilize thermal decomposition method and electrodip process to prepare nanocrystalline manganese bioxide coated anode; overcome that used anode material costs an arm and a leg in the prior art; the shortcoming that oxidation-resistance is relatively poor can be used for hypochlorite generator's anode material.

In order to solve the problems of the technologies described above, the technical solution adopted in the present invention is as follows:

Nanocrystalline manganese bioxide coated anode comprises three layers, and the first layer is the valve metal base layer, and the second layer is the anti-oxidation protection middle layer, and the 3rd layer is the nanocrystalline manganese bioxide Catalytic Layer.The valve metal matrix is any in aluminium, tantalum, niobium, the titanium; The anti-oxidation protection middle layer is made of one of metal oxide containing precious metals, stannic oxide and weisspiessglanz at least, is preferably the mixture of iridium dioxide or stannic oxide and weisspiessglanz; The coating total amount of nanocrystalline manganese bioxide Catalytic Layer is 10-20gm ^-2

The present invention includes a kind of preparation method of above-mentioned manganese dioxide anode; described method is included in the middle layer that applies anti-oxidation protection on the valve metal matrix, adopts thermolysis or anodic electrodeposition legal system to be equipped with the Manganse Dioxide Catalytic Layer on the middle layer that applies corresponding organic or inorganic salt.

Concrete processing step is as follows:

At first, the matrix of selecting is carried out sandblast, harsh processing obtaining coarse surface, thereby guarantee the connection between matrix and the middle layer.

To apply chloro-iridic acid, propyl carbinol and ethanol mixing masking liquid on the matrix, carried out thermolysis 5-15 minute at 300-600 ℃ after 100～150 ℃ of oven dry, repetitive coatings 3～5 times at 300～600 ℃ of following sintering 40～60min, just generates uniform iridium oxide layer then; Or by applying by SnCl ₄And SbCl ₃The masking liquid that the configuration of the mixing solutions of hydrochloric acid and propyl carbinol forms, after 100～150 ℃ of oven dry in 450～550 ℃ of following sintering 5～15min, repetitive coatings 3～5 times, at 450～550 ℃ of following sintering 40～60min, just generate uniform tin-antimony oxide layer then at matrix surface.Afterwards, adopt thermal decomposition method or employing anodic electrodeposition method to prepare nanocrystalline manganese bioxide coated.

The liquid formula that is coated with in preparation iridium oxide middle layer is: chloro-iridic acid concentration is 0.2～0.5mol/L, and propyl carbinol and alcoholic acid volume ratio are 1: 2～2: 1; The liquid formula that is coated with in preparation tin-antimony oxide middle layer is: Sn, Sb atomic ratio are 1: 1～9: 1, total ion concentration 0.2～0.5mol/L, and hydrochloric acid and propyl carbinol volume ratio are 1: 2～1: 1.

Select to adopt thermal decomposition method to prepare manganese bioxide coated: with hairbrush with 30～60wt%Mn (NO ₃) ₂Masking liquid is coated on the surface for preparing the middle layer, 90～150 ℃ of down dry 5～15min, and afterwards at 100～500 ℃ of following thermolysis 5～10min, this process repeats 8～15 times, for the last time at 100～500 ℃ of following sintering 10～40min.Or select to adopt the anodic electrodeposition method to prepare manganese bioxide coated: electroplate liquid adopts 0.5～2moldm ^-3MnSO ₄+ 0.3～1moldm ^-3H ₂SO ₄, current density is 10～50mAcm ^-2, temperature is an anodic electrodeposition under 80～95 ℃ the condition.Adopting thermolysis or anodic electrodeposition method to make the heap(ed) capacity of Manganse Dioxide Catalytic Layer is 10～20gm ^-2

The present invention adopts the middle layer of adding protectiveness; utilize Manganse Dioxide high corrosion-resistant and oxidation resistant characteristics in acid-basicity solution; utilize the prepared nanocrystalline manganese bioxide coated anode that goes out of thermal decomposition method and electrodip process; through polarization curve; electrochemical impedance spectroscopy; accelerated life test; the electrolytic simulation analytical test; its result shows: the contact resistance among the present invention between matrix and the coating significantly reduces; and can significantly delay the rising of contact resistance; nanocrystalline manganese bioxide anodic resistance of oxidation is strong; electrocatalysis characteristic is good; can replace noble metallic oxide anode and be used for the hypochlorite generator, significantly reduce cost.

Description of drawings

Fig. 1 is the SEM figure in iridium dioxide middle layer.

Fig. 2 is the manganese bioxide coated SEM figure that thermal decomposition method directly prepares.

Fig. 3 is SnO ₂The SEM figure in+SbOx middle layer.

Fig. 4 is the manganese bioxide coated SEM figure of anodic electrodeposition method preparation.

Fig. 5 is the structural representation of manganese bioxide coated anode.

Embodiment

Below in conjunction with accompanying drawing and preferred implementation the invention technical scheme is carried out concrete description.

Preferred implementation 1

Select pure titanium plate as matrix, and cut into the desired size size.In order to increase the matrix surface roughness, improve the bonding force be coated with (plating) layer and matrix, prevent to be coated with coming off of (plating) layer, before use, at first matrix being carried out commercial blast and handle, remove surface and oil contaminant, is 20% oxalic acid solution at last with concentration, 90 ℃ with the titanium matrix soak about 30min be deep yellow to solution till, more respectively with tap water, deionization washing, oven dry.Pass through the matrix of pre-treatment and can observe the deep mixed point corrosion pit of size at microscopically, do not compare with passing through the pre-treatment matrix, the roughness of matrix surface increases greatly.

Adopt pyrolysated method coating sintering IrO on above-mentioned treated titanium matrix ₂The protectiveness middle layer.Adopt chloro-iridic acid, propyl carbinol and alcoholic acid mixing solutions as masking liquid, wherein chloro-iridic acid concentration is 0.23mol/L, and propyl carbinol and ethanol volume ratio are 1: 1.Masking liquid is brushed equably on the titanium matrix, and at 450 ℃ of following sintering 10min, repetitive coatings 3 times at last at 450 ℃ of sintering 60min, generates iridium oxide layer after 100 ℃ of oven dry.

Use 50wt%Mn (NO at last ₃) ₂Masking liquid is coated on the surface for preparing the middle layer with hairbrush, 90 ℃ of following dry 10min, and afterwards at 200 ℃ of following thermolysis 5min, this process repeats 10 times, and at last at 350 ℃ of following sintering 20min, the heap(ed) capacity that makes the Manganse Dioxide Catalytic Layer is 12gm ^-2

Fig. 1 shows IrO ₂The middle layer mainly is made of discrete isolated island shape structure, and is covered with apparent crackle in the island structure.But from integral body, coatingsurface is dense, evenly.As can be seen from Figure 2, the manganese bioxide coated of thermal decomposition method preparation is the Nanoparticulate structure, and diameter is approximately 30-50nm, illustrates that reactive activity point is more, thereby helps improving the catalytic activity of electrode.Accelerated test is to adopt the standard of test anode oxidation test in hypochlorite generator's national standard to carry out, and test shows Ti/IrO ₂/ MnO ₂The anodic accelerated aging reaches 215 hours, considerably beyond 20 hours level of national standard A level.

Preferred implementation 2

Select pure titanium plate as matrix, and according to sandblast, etching processing before preferred implementation 1 disclosed method applies the titanium matrix.Adopt pyrolysated method coating sintering SnO on above-mentioned treated titanium matrix ₂+ SbOx protectiveness middle layer.Masking liquid is by SnCl ₄And SbCl ₃, the mixing solutions configuration of hydrochloric acid and propyl carbinol forms, and wherein Sn, Sb atomic ratio are 7: 3, total ion concentration 0.2mol/L, hydrochloric acid and propyl carbinol volume ratio are 1: 1.

Masking liquid is brushed equably on the titanium matrix surface after the processing, and at 500 ℃ of following sintering 10min, repetitive coatings 3 times at 500 ℃ of following sintering 60min, just generates uniform tin-antimony oxide layer at last after 100 ℃ of oven dry.On the middle layer, apply the Manganse Dioxide Catalytic Layer according to preferred implementation 1 disclosed method at last.Fig. 3 shows, the middle layer SnO of preparation ₂+ SbOx middle layer and IrO ₂The middle layer is the same to be made of isolating isolated island shape structure, and manganese bioxide coated is the Nanoparticulate structure, and diameter is approximately 30-50nm, Ti/SnO ₂+ SbOx/MnO ₂The anodic accelerated aging reaches 140 hours.

Preferred implementation 3

Adopt in the above-mentioned preferred implementation disclosed method that the titanium matrix is carried out sandblast, etching also press embodiment 1 coating middle layer.Adopt the method deposition Manganse Dioxide Catalytic Layer of anodic electrodeposition.Anodic electrodeposition is mainly finished by following three steps:

Mn ²⁺→Mn ³⁺ (1)

Mn ³⁺+2H ₂O→MnOOH+3H ⁺ (2)

MnOOH→MnO ₂+e+H ⁺ (3)

Electroplate liquid adopts 1moldm ^-3MnSO ₄+ 0.5moldm ^-3H ₂SO ₄, current density is 20mAcm ^-2, temperature is to electroplate under 90 ℃ the condition.The Manganse Dioxide of electrodip process preparation shown in Figure 4 is mainly γ-MnO ₂, having nanometer fibrous tissue, mean diameter is 9nm, length is 100nm.The accelerated aging of the manganese bioxide coated anode of preparation is with the difference in middle layer, and accelerated aging is difference to some extent, but all can be above 100 hours.

Fig. 5 has shown the structure that adopts the nanocrystalline manganese bioxide coated electrode of preparation; the lowest layer is the titanium matrix; body portion oxidation and the zone of oxidation that forms in preparation process are arranged on it, and what apply on it is the middle layer of protectiveness, and the superiors are the Manganse Dioxide Catalytic Layer.

Selection concentration is 35gL ^-1The sodium-chlor of 200mL be electrolytic solution, select different parameters, the nanocrystalline manganese bioxide coated electrode of preparation has been carried out the test that static electrolysis lower concentration chlorination sodium generates clorox.Adopt iodimetry,iodometry to measure efficient concentration (ACH).Current efficiency can be defined as whereby:

$\mathrm{\&eta;}=\frac{\mathrm{measuredACHconcentration}}{\mathrm{theoreticalACHcontration}}\&times;100\%---\left(4\right)$

Electrolysis Cl ^-Generate a Cl ₂Need to consume two electronics, according to Faraday's law, the formation speed that can derive generation chlorine is:

$\frac{\mathrm{dm}}{\mathrm{dt}}=\frac{35.5}{F}\mathrm{ISa\&eta;}\left({\mathrm{gs}}^{-1}\right)---\left(5\right)$

Behind the conversion unit, can obtain:

$\frac{\mathrm{dm}}{\mathrm{dt}}=22.08\mathrm{ISa\&eta;}\left({\mathrm{mg}\min }^{-1}\right)---\left(6\right)$

Wherein I is current density (Acm ^-2), Sa is anodic area (cm ²), F=96485C.

The electrolytic trial result shows that the current efficiency of the nanocrystalline manganese bioxide coated anode of preparation is 75%-80%.

Matrix in an embodiment of the present invention can also adopt other valve metal except that titanium, and other metal oxide containing precious metals or its mixture also can be adopted except that iridium dioxide in the middle layer of protectiveness.

Claims (6)

1. a nanocrystalline manganese bioxide coated anode is characterized in that, nanocrystalline manganese bioxide coated anode comprises three layers, and the first layer is the valve metal base layer, and the second layer is the anti-oxidation protection middle layer, and the 3rd layer is the nanocrystalline manganese bioxide Catalytic Layer.

2. nanocrystalline manganese bioxide coated anode as claimed in claim 1 is characterized in that, the valve metal matrix is any in aluminium, tantalum, niobium, the titanium.

3. nanocrystalline manganese bioxide coated anode as claimed in claim 1 is characterized in that the anti-oxidation protection middle layer is made of one of metal oxide containing precious metals, stannic oxide and weisspiessglanz at least, is preferably the mixture of iridium dioxide or stannic oxide and weisspiessglanz.

4. nanocrystalline manganese bioxide coated anode as claimed in claim 1 is characterized in that, the coating total amount of nanocrystalline manganese bioxide Catalytic Layer is 10-20gm ^-2

5. the preparation method of the described nanocrystalline manganese bioxide coated anode of claim 1 carries out sandblast, harsh processing to matrix, it is characterized in that preparation process is:

1) preparation middle layer: on matrix, apply chloro-iridic acid, propyl carbinol and ethanol mixing masking liquid, carried out thermolysis 5-15 minute at 300-600 ℃ after 100～150 ℃ of oven dry, repetitive coatings 3～5 times then at 300～600 ℃ of following sintering 40～60min, generates iridium oxide layer; Or by applying by SnCl ₄And SbCl ₃, the masking liquid that the mixing solutions configuration of hydrochloric acid and propyl carbinol forms, at 450～550 ℃ of following sintering 5～15min, repetitive coatings 3～5 times then at 450～550 ℃ of following sintering 40～60min, generates the tin-antimony oxide layer after 100～150 ℃ of oven dry;

2) preparation is manganese bioxide coated: adopt thermal decomposition method or anodic electrodeposition method, when selecting thermal decomposition method, with hairbrush with 30～60wt%Mn (NO ₃) ₂Masking liquid, be coated on the surface for preparing the middle layer, 90～150 ℃ of down dry 5～15min, again at 100～500 ℃ of following thermolysis 5～10min, this applies and thermal decomposition process repeats 8～15 times, at 100～500 ℃ of following sintering 10～40min, select the anodic electrodeposition method to prepare manganese bioxide coated: electroplate liquid adopts 0.5～2moldm for the last time ^-3MnSO ₄+ 0.3～1moldm ^-3H ₂SO ₄, current density is 10～50mAcm ^-2, temperature is 80～95 ℃.

6. nanocrystalline manganese bioxide coated anode preparation method as claimed in claim 5 is characterized in that, the liquid formula that is coated with in preparation iridium oxide middle layer is: chloro-iridic acid concentration is 0.2～0.5mol/L, and propyl carbinol and alcoholic acid volume ratio are 1: 2～2: 1; The liquid formula that is coated with in preparation tin-antimony oxide middle layer is: Sn, Sb atomic ratio are 1: 1～9: 1, total ion concentration 0.2～0.5mol/L, and hydrochloric acid and propyl carbinol volume ratio are 1: 2～1: 1.

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