Method of making electrode for electrochemical processes

FIELD: chemistry.

SUBSTANCE: method of making an electrode for electrochemical processes involves electrodeposition of an electrocatalytic coating based on mixed oxides of base metals on a titanium surface. The said coating on the titanium surface is formed through electrodeposition from an aqueous solution of an electrolyte which contains salts of cobalt, manganese, nickel and boric acid under the effect of alternating asymmetrical current in which the current amplitude ratio of the anode and cathode half-cycles is 2:1, at voltage of 8-10 V, with the following ratio of components (g/l): cobalt sulphate (CoSO47H2O) - 100.0-110.0, manganese sulphate (MnSO45H2O) - 20.0-25.0, nickel sulphate (NiSO47H2O) - 15.0-20.0, boric acid (H3BO3) - 25.0-30.0, with subsequent thermal treatment in an oxidising atmosphere at 350-380C for 30 minutes.

EFFECT: invention increases corrosion resistance and electrocatalytic activity of the electrode, increases bonding strength of the coating with the titanium substrate, reduces the cost of making the electrode and energy consumption of the process.

1 tbl, 1 ex

 

The invention relates to the field of technical electrochemistry, in particular the production of metal oxide anodes consisting of a substrate of a valve metal and an active oxide coating, and can be used for electrolysis of chloride solutions and electrosynthesis.

A method of obtaining an electrode, which constitutes the basis of titanium or its alloys with an electrocatalytic coating of oxides of ruthenium and titanium in a ratio (mol. %) 25-30:70-75, contains intermediate sublayers of titanium oxide formed by plasma-electrolytic oxidation [U.S. Pat. RU # 2288973. Electrode and method of its making. Kondrikov NB, Scitovsky E.V., Vasilyev, MS, Rudnev V.S., Tyrina L.M. 2006. Bull. No. 34]. The disadvantages of this method are:

- high energy consumption due to the need to pre-formation between the base and electrocatalytic coating intermediate layers of titanium oxide obtained by the method of plasma-electrolytic oxidation at a voltage of 100-300;

- use composition of the electrocatalytic coating of expensive components (RUO Li2);

- not enough high electrocatalytic characteristics of the electrode.

The closest in technical essence and the achievable result for the proposed method is the way technology is increasing oxide-cobalt electrode by coating on a titanium substrate from the aqueous solution of cobalt salts in the form of a mechanical mixture of cobalt hydroxide and cobalt metal by using a rectangular pulse current density 130-160 A/DM2with a subsequent heat treatment in an oxidizing atmosphere at 340-420C [Pat. SU # 1286639, SW 11/10. Method of manufacturing oxide-cobalt electrode. Storm I.A., spnu VK, Fur D.M., Shalaginov CENTURIES, Folgender I.N., Abani S.D. 1987. Bull. No. 4]. The disadvantages of this method are:

- very energy intensive process, as it uses a very large current density, about 130-160 A/DM2;

- high cost of coverage due to the fact that it is necessary expensive equipment;

- not enough high corrosion resistance and electrocatalytic characteristics of the electrode;

the low adhesion of the coating to the substrate.

The objective of the invention is to reduce the energy intensity of the process; reduce the costs of manufacturing metal oxide electrode and improving its corrosion resistance and electrocatalytic activity; the increase in the adhesion strength of the coating with a titanium substrate.

The task is achieved by a method of producing an electrode for electrochemical processes, consisting in the electrodeposition electrocatalytical coating on the surface of Titan, despite the fact that the electrocatalytic coating on the surface of titanium is formed on the basis of mixed oxides of base metals by electrodeposition from an aqueous solution El is trolyte, containing, in terms of crystalline, salts of cobalt, manganese, Nickel and boric acid under the action of the asymmetric AC voltage, in which the ratio of the amplitude of the anodic and cathodic currents

half-periods is 2:1, at a voltage of 8-10, in the following ratio of components (g/l):

Cobalt sulphate (CoSO47H2O) - 100,0-110,0

Manganese sulfate (MnSO45H2O) - 20,0-25,0

The Nickel sulfate (with NISO47H2O) - 15,0-20,0

Boric acid (H3IN3) - 25,0-30,0

with a subsequent heat treatment in an oxidizing atmosphere at 350-380C. Using asymmetric AC current allows in the cathode half precipitate from the electrolyte on the surface of titanium metal ions included in the salt contained in the electrolyte solution and the anode to oxidize them to oxides. As a result of processes of Cycling on the surface of titanium is formed of electrocatalytically active coating based on mixed oxides of base metals, with the structure of rutile and corundum or rutile and spinel, which has high adhesion to the substrate.

Through the use of asymmetric AC current achieved high efficiency of the electrode. As was received multiphase coating with a developed system of interphase boundaries and some variety is necessary for p is aktionscode application of physico-chemical properties. This gave the purposeful regulation of electrophysical and elektrokataliticheskikh properties of solid-phase electrode.

The proposed method of producing metal oxide electrode on the titanium base enabled:

- to simplify the process, eliminating the stage of forming an intermediate layer between the base and electrocatalytic coating. His role oxides with spinel structure, which are formed during Cycling;

to reduce energy costs about 10 times as electrolytic coating is obtained when the voltage of 8-10 and average current density of 0.08 A/DM2;

- exclude the presence of costly components in the coating composition and thereby reduce its cost;

- to provide high electrocatalytic characteristics of the electrode due to the developed system of interphase boundaries in a multicomponent system;

to increase the strength of adhesion of the coating to the substrate due to the presence of the transition layer of oxides with spinel structure, which is formed in the process of circulation.

The novelty in the present invention is a method of producing an electrode for electrochemical processes on the basis of mixed oxides of base metals on the surface of Titan.

The electro-deposition of oxides of base metals (cobalt, manganese, Nickel) ASU is actulaly on prepared surface flat samples of titanium VT1-0, area of 10501 mm when the polarization variable asymmetric shock, triangular, 50 Hz, with equal duration of anodic and cathodic pulses, at a certain ratio of the amplitude of the currents of anodic and cathodic half-cycle in acidic electrolyte containing salts of cobalt, manganese, Nickel and buffer additive (H3IN3).

The cathode used plates made of stainless steel. The electrolysis was carried out at a temperature of 40-45C and a stirring solution of electromagnetic stirrer. The duration of the formation of the oxide film was 60 minutes

For experimental verification of the proposed method were formed electrocatalytic layers on the basis of oxides of base metals on the surface of titanium VT1-0.

Example. Flat plate titanium VT1-0 size of 10501 mm, pre-machined with abrasive material, etched in 10%oxalic acid at 90C for 30 min and thoroughly washed with distilled water. The prepared samples were immersed in the electrolyte of the following composition, g/l:

Cobalt sulphate (CoSo47H2O) - 100,0-110,0

Manganese sulfate (MnSO45H2O) - 20,0-25,0

The Nickel sulfate (with NISO47H2O) - 15,0-20,0

Boric acid (H3IN3) - 25,0-30,0

and received electrocatalytic coating when the ratio is AI the average of anodic and cathodic components of current 2:1, the voltage 8-10, a temperature of 40-45C, followed by heat treatment in an oxidizing atmosphere at 350-380C for 30 minutes

The morphology, phase composition and structure of the electrocatalytic coating on the surface of titanium was investigated using scanning microscope QUANTA 200, x-ray microanalysis in the electron microscope using Camebax - micro (France) and scanning electron microscopy for electron microscope LEM-100 CX ("JEOL", Japan).

The coating has a color similar to the oxide-ruthenium anode (ORT), and is well linked with the base. The electrode electrocatalytic coating thus obtained was tested in the reaction selection of active chlorine from a solution of 300 g/l sodium chloride at an anode current density of 1000 a/m2. All electrochemical characteristics of the electrode was not inferior to the anode with a stable size (Dimensial stable anodes - DSA), which is ORTA. The electrode potential was 0,837 In and over 7200 hours of testing have not changed. Corrosion was 0,020 mg/cm2H.

Comparative electrochemical characteristics of the electrode, obtained by the proposed method, and ORT is given in table 1

Table 1
Characteristics and indicators about the ECCA electrolysis electrode, obtained by the proposed method, and ORTA
ElectrodeW act. chlorine, %The potential of the anode, In, NVA at i=0.2 a/cm2Voltage
of,
The rate of destruction, mg/(cm2h)Thickness, micronsPhase composition
Manufacturing
Lenna
68,00,8374,20,02015,0Rutile and corundum or rutile and spinel
Receiving-
to
a prototype is
PU
55,01,3504,0to 0.06015,0rutelinae phase

Based on the above data it is seen that the electrodes obtained by the proposed method on titanium-based, are compared to known the following advantages:

- allow to increase the electrocatalytic activity of the anode and increase the selectivity to the formation of active chlorine;

- exclude precious metals in the coating, which leads to a significant reduction of the of electrode, used in heavy electrochemical industries.

A method of producing an electrode for electrochemical processes, consisting in the electrodeposition electrocatalytic coating on the surface of Titan, wherein the electrocatalytic coating on the surface of titanium is formed on the basis of mixed oxides of base metals by electrodeposition from an aqueous solution of an electrolyte containing salts of cobalt, manganese, Nickel and boric acid under the action of the asymmetric AC voltage, in which the ratio of the amplitude of the currents of anodic and cathodic half-cycle is 2:1, at a voltage of 8-10 In the following ratio of components, g/l:

cobalt sulphate (CoSO47H2Oh)100,0-110,0
manganese sulfate (MnSO45H2O)20,0-25,0
the Nickel sulfate (with NISO47H2O)15,0-20,0
boric acid (H3IN3)25,0-30,0,

with a subsequent heat treatment in an oxidizing atmosphere at 350-380C for 30 minutes



 

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