PL153305B1 - Method of obtaining a ceramic electrode material based on titanium oxides - Google Patents

Description

RZECZPOSPOLITA PATENT DESCRIPTION 153 305 POLAND

Ar

Additional patent to patent no. - Filed: 88 09 12 (P. 274624)

Precedence - Int. Cl. ⁵ C04B 35/46

OFFICE

PATENT

RP unuiu o 6 Ili a

Application announced: 90 03 19

Patent description published: 1991 09 30

Creators of the invention: Jan Przyłuski, Krzysztof Borowiec, Romuald Juchniewicz,

Jerzy Walaszkowski, Władysław Bohdanowicz, Wojciech Sokolski

The holder of the patent: Warsaw University of Technology,

Warsaw Poland)

A method of producing a ceramic electrode material based on titanium oxides

The present invention relates to a method of producing a titanium oxide-based ceramic electrode material.

From the United States patent specification No. 4,222,917 a method of obtaining ceramic electrodes from titanium dioxide by reduction with a gas reducer is known. The anodes made of the electrode material obtained in this way are characterized by a high release voltage of oxide and chlorine, amounting to about 2000 mV. This over-voltage can be significantly reduced by electrochemically coating the anodes with active compounds, for example PbO2 or RuO2. This method of lowering the overvoltage value, however, leads to inhomogeneity of the electrode surface and surface oxidation, which increases the resistivity.

The aim of the invention was to develop a technology that makes it possible to obtain an electrode material based on titanium oxides with improved electrical conductivity and, at the same time, a reduced value of the oxygen, chlorine and hydrogen evolution overvoltage, and with a reduced proton intercalation potential and increased current density, compared to known materials.

This object has been achieved by using the method for producing a titanium oxide ceramic electrode material according to the invention.

The method according to the invention consists in reacting the gelite or its oxygen compounds into non-stoichiometric oxides of the homologous titanium series of the general formula TinO2n-i, in which n is from 4 to 10, and reacted with transition metals of the group V and / or VI the periodic table. These metals are introduced in an amount corresponding to the mole ratio of titanium to the doped metal from 1: 200 to 1: 1.

Doped metals can be introduced in an oxidizing atmosphere at a temperature of 80 (- 1500 ° C) and the resulting oxidation product can be reduced at a temperature of 800-1500 ° C, titanium being best used in the form of powdered metal, titanium dioxide or metatitanic acid. they can be introduced in the form of powdered metals or their oxides, titanium and metals can also be used in the form of their powdered alloys.

The doped metals can also be introduced under a reducing atmosphere at a temperature of 800-1500 ° C and the resulting product optionally further calcined in an inert atmosphere at a temperature of 900-1500 ° C. When the dopants are added in a reducing atmosphere, it is preferable to use titanium in the form of titanium dioxide or metatitanic acid, and doped metals in the form of powders or oxides.

Due to the introduction of the dopants of transition metals to the structure of non-stoichiometric titanium oxides by the method according to the invention, a new electrode material is obtained, which is characterized by increased electric conductivity, a reduced value of the oxide and chlorp release overvoltage by about 1 V, and a reduced thermodynamic activity, and thus increased corrosion resistance made of electrodes compared with known materials.

Using the method according to the invention, an electrode material of the general formula Τί _η -χΜχθ2η- ^ ι is obtained, wherein M is a doped metal, X is its amount, and n is as defined above. This material can be obtained in the form of granules, powders or in the form of ready-made electrodes.

Depending on the moment of introducing the dopant into the structure of non-stoichiometric titanium oxides, an electrode material with different pore size and microstructure, different mechanical strength and different electrochemical properties is obtained. When doping in an oxidizing atmosphere, roasting at high temperature with the oxides of the introduced metals will force the diffusion of the cations of these metals, which affects the microstructure of the oxidation product and hence the microstructure of the reduction product. On the other hand, when introducing admixtures under conditions reducing oxygen removal, shear planes occur during reduction. Oxygen is simultaneously removed from the titanium dioxide and from the admixture, which is accompanied by the diffusion of admixture cations into the structure of the oxide formed.

The electrode material produced by the method of the invention can be used in a variety of ways, depending on the composition obtained. For example, the material with the composition Ti4-xM _x O7 or Τΐ5-χΜχθ9 can be used as an anode material in cathodic protection systems, for the separation of metals such as gold, silver, copper, platinum, nickel, chromium, zinc or cobalt from aqueous solutions. as an anode and / or cathode. Electrodes made of these materials can be used to obtain MnO ₂ by electrolysis of MnSO4 solution and to obtain chlorates and perchlorates from NaCl aqueous solution. In addition, anodes can be used in electroplating for the production of Ag, Ni, Cr, Cd, Fe coatings and their alloys. They can also be used in organic electrosyntheses.

On the other hand, solid solutions of higher titanium oxides with Nb or Ta, such as Tie-xNb _x Oi5 and Ti9- _x NbxOi7, due to their greater resistivity, can be used as a heating element for food liquids, for example in the homogenization of milk due to the non-toxicity of these materials.

The electrode material obtained by the method according to the invention can also find application in photovoltaic cells as a photoanode, and produced in the form of granules can be used as an anode powder in cathodic protection systems.

The subject of the invention is explained in more detail in the working examples.

Example 1 To 500 g of pigment T1O2 from the sulphate method 10.65 g of Nb ₂ Os were added and mixed thoroughly. Then 5.1 g of bentonite binder and about 7% by weight of distilled water were added. Disc-shaped compacts with a diameter of 44 mm and a height of 5 mm were made from the obtained mixture on a uniaxial hydraulic press at a pressing pressure of 100 kg / cm2. The compacts were then reduced with hydrogen at 1050 ° C for 4 hours. After the end of the process, the reduction product was cooled to room temperature under a hydrogen atmosphere at a rate of 60 ° C / min. The product obtained had the composition of Tie ^ sNbo.osCb and the pore fraction r®3 · 102 nm amounting to about 50%.

Example II. 1000 g of TiO2 pigment method sulphate was mixed with 21.30 g of Nb2Os, and thoroughly wet-mixed using 250 cm ^{3 of} isopropyl alcohol and water in a ratio of 1: 1. After drying in an oven at 70 ° C, the mixture was calcined at

Atmosphere in a chamber furnace at 1200 ° C for 4 hours. After cooling, 7% by weight of polyethylene oxide in an aqueous solution was added to the mixture as a binder. The whole was thoroughly mixed and dried at the temperature of 45 ° C, and then the compacts were made in the manner and conditions as in Example 1. The compacts were reduced with hydrogen at 1050 ° C for 4 hours. The ceramic electrode material was obtained, single-phase with the composition Ti3.95, Nbo.osO?, In which pores with radius r> 10 ³ nm predominated, and pores with radius r = 5'10 ³ nm constituted 45%.

Example III. To 500 g of powdered titanium, 28.4 g of Nb ₂ Os were added, and after thorough mixing, about 7% by weight of polyethylene oxide was added as an aqueous solution. After drying the mixture, compacts 30 mm in diameter and 4 mm in height were made using a pressure of 750 KG / cm ^{1 2} . The compacts were oxidized in air at 1200 ° C for 4 hours. As a result of the oxidation, a shaped body with a very high flexural strength was obtained, amounting to 55 KG / m2. The piece was reduced with hydrogen at 1050 ° C for 5 hours, obtaining an electrode material composed of Ti3.92Nbo, os07, which has 45% pores with a radius r = 10 nm.

* Example IV. 1000 g of metatitanic acid was mixed with 27.8 g of Nb ₂ Os, and after thorough mixing, 7% by weight of polyethylene oxide in aqueous solution was added. After drying, moldings with a diameter of 30 mm and a height of 4 mm were made from the obtained mixture, using a pressure of 1500 KG / cm2. The compacts were reduced with hydrogen at 1050 ° C for 4 hours. After this time, the water supply was shut off and after the temperature was increased to 1350 ° C, the moldings were roasted at this temperature for another 1 hour. The obtained electrode material was pore-free, single-phase with the composition Ti3.92Nbo, oo07 and with a density close to theoretical, amounting to 4.15 g / cm ³ .

EXAMPLE 5 1000 g of T1O2 clinker with a grain diameter of less than 0.1 mm were mixed with 34 g of Nb2Os and after mixing, 7% by weight of polyethylene oxide was added as an aqueous solution. The mixture was air-dried and then formed into compacts 44 mm in diameter and 5 mm in height on a uniaxial press using a pressing pressure of 500 KG / cm2. The compacts were calcined in the air atmosphere at the temperature of 1200 ° C for 4 hours. The material obtained had about 65% of pores with a diameter of 2 * 10 mm and a flexural strength of 15 KG / mm.

Example VI. 1000 g of TiO2 clinker with particle size below 0.04 mm was mixed with 89.4 g of titanium powder with particle size below 0.04 mm and with 24.2 g of Nb2Os with particle size below 0.025 mm. The whole was thoroughly mixed and 5% by weight of polyethylene oxide was added as an aqueous solution. After the mixture was air-dried, compacts were molded with dimensions and conditions as in Example 4. The compacts were then calcined in an anaerobic atmosphere at a temperature of 1200 ° C for 8 hours. The obtained electrode material was Ti3.95Nbo, 05O7.

Example VII. 1000 g of TiO2 clinker with a grain size of about 0.04 mm were mixed with 100 g of graphite and 14.4 g of V2O ₅ . After thorough mixing, 7% by weight of polyethylene oxide was added as an aqueous solution. The mixture was air dried and molded into compacts with dimensions as in Example 4. The compacts were calcined in air at 600 ° C for 2. hours, and after increasing the temperature to 1000 ° C the compacts were roasted for another 2 hours.

Porous bodies were obtained which were reduced with hydrogen at 1100 ° C for 4 hours. A ceramic, porous electrode material with the composition Ti3.95Vo, o507 was obtained.

Example VIII. Under the conditions and the method as in Example 7, with the difference that the compacts were reduced at 1050 ° C for 3 hours, a ceramic, porous electrode material was obtained with the composition Ti4.95Vo, oo09.

Claims (5)

Patent claims A method for the production of a titanium oxide-based ceramic electrode, characterized in that titanium or its oxygen compounds, after optionally converting them into non-stoichiometric oxides of the homologous titanium series of the general formula Ti _n O2n-i, in which n 153 305 from 4 to 10 are reacted with the transition metals of groups V and / or VI of the periodic table introduced in an amount corresponding to a mole ratio of titanium to the doped metal from 1: 200 to 1: 1. 2. The method according to p. The process of claim 1, characterized in that the doped metals are introduced in an oxidizing atmosphere and reacted with titanium at a temperature of 800-1500 ° C, then the obtained oxidation product is reduced at a temperature of 800-1500 ° C. 3. The method according to p. A process as claimed in claim 2, characterized in that the titanium is introduced in the form of powdered metal, titanium dioxide or metatitanic acid and the admixtures are in the form of powdered metals or their oxides. 4. The method according to p. The process of claim 1, characterized in that the doped metals are introduced under a reducing atmosphere and reacted with titanium at a temperature of 800-1500 ° C, and the obtained product is optionally further calcined in an inert atmosphere at a temperature of 900-1500 ° C. 5. The method according to p. 4. A process as claimed in claim 4, characterized in that the titanium is introduced in the form of titanium dioxide or metatitanic acid, and the dopants in the form of powdered metals or their oxides. Department of Publishing of the UP RP. Circulation 100 copies Price: PLN 3,000