CN103884752B - For studying the electrolytic cell of the electroactive oxide electrochemical behavior of fused electrolyte - Google Patents

Abstract

The invention relates to an electrolytic cell for studying the electrochemical behavior of electroactive oxides in a molten electrolyte. Its technical scheme is: electrolytic cell comprises ZrO ₂ tube (3), reference electrode (15), auxiliary electrode (1) and solid-state working electrode (2) _{; 2} The outer surface of the closed end of the tube (3) is sintered from bottom to top with an auxiliary electrode (1) and a reference electrode (15), the upper boundary of the auxiliary electrode (1) is in contact with the molten electrolyte in the ZrO2 tube ( ₃ ) The surface is flush, the reference electrode (15) is close to the upper boundary of the auxiliary electrode (1), the lower end of the solid working electrode (2) is inserted into the molten electrolyte; one end of the reference electrode lead (4), one end of the auxiliary electrode lead (7) and One end of the lead wire (8) of the solid-state working electrode is correspondingly connected with the reference electrode (15), the auxiliary electrode (1) and the solid-state working electrode (2). The invention has the characteristics of simple structure, easy operation, strong anti-interference ability and more stable and reliable test results.

Description

Electrolytic cells for studying the electrochemical behavior of electroactive oxides in molten electrolytes

technical field

The invention belongs to the technical field of electrolytic cells. In particular, it relates to an electrolytic cell for studying the electrochemical behavior of electroactive oxides in a molten electrolyte.

Background technique

Electrolysis of metal oxides in molten electrolytes is a fundamental method for the green preparation of metals. Metal oxides generally dissociate into metal cations and oxygen ions in the molten electrolyte. During electrolysis, metal cations are reduced at the cathode to obtain metals; while oxygen ions are oxidized at the anode to produce oxygen. In order to formulate a reasonable electrolysis process route, it is necessary to grasp the redox law of the electroactive ions corresponding to the metal oxides prepared in the molten electrolyte.

At present, the research on the electrochemical behavior of electroactive substances is generally carried out in a three-electrode electrolytic cell system. However, the testing and research of electrochemical behavior at high temperature is limited by the stability of the electrode (especially the reference electrode) and the electrolytic cell container on the one hand; on the other hand, it is also limited by the electronic conductivity of the molten electrolyte itself and the non-oxidizing Interference with impurities. Moreover, in order to prevent the different polar regions from interfering with each other, an ion isolation membrane should generally be installed in the electrolytic cell, but the material selection of the ion isolation membrane will be more difficult at high temperatures. The above-mentioned multiple reasons lead to high temperature electrochemical test research not only has great difficulties in the operation of the electrolytic cell, but also has an adverse effect on the reliability and stability of the test results. ZrO ₂ doped with MgO or Y ₂ O ₃ is a solid electrolyte that conducts oxygen ions. It has selective permeability only for oxygen ions and has good stability at high temperatures. It can be used as a separator for electrolytic cells or container. "An electrolytic cell for measuring the decomposition voltage of iron oxides in molten slag" ( _{CN201310668235.3} ) patent technology provides an electrolytic cell using ZrO2 solid electrolyte to measure the decomposition voltage of iron oxides in molten slag. Only two electrodes are set, although it is possible to carry out related research such as slag electrolysis, but it is difficult to carry out stable and reliable research and testing of the electrochemical behavior of electroactive ions.

Contents of the invention

The invention aims to overcome the defects of the prior art, and aims to provide an electrolytic cell for studying the electrochemical behavior of electroactive oxides in molten electrolytes with simple structure, easy operation, strong anti-interference ability and stable and reliable test results.

In order to achieve the above object, the technical scheme adopted by the present invention is: the electrolytic cell includes a ZrO2 tube, a reference electrode, an auxiliary electrode and a solid _- state working electrode. The closed end of the ZrO ₂ tube is equipped with molten electrolyte, and the open end of the ZrO ₂ tube is equipped with an alumina plug; the outer surface of the closed end of the ZrO ₂ tube is surrounded by sintering from bottom to top with an auxiliary electrode and a reference electrode. _The boundary is flush with the molten electrolyte in the ZrO2 tube, and the reference electrode is close to the upper boundary of the auxiliary electrode; one end of the reference electrode lead is fixedly connected to the reference electrode, and one end of the auxiliary electrode lead is fixedly connected to the auxiliary electrode.

_The lower half of the air intake tube is inserted into the ZrO2 tube through the center hole of the alumina plug, and an exhaust hole is arranged beside the center hole of the alumina plug. The upper port of the tube is sealed and connected with the lower port of the T-shaped three-way pipe through a rubber tube; the upper port of the T-shaped three-way pipe is provided with a rubber plug, and the side port of the T-shaped three-way pipe is an inert gas inlet.

The upper end of the insulating tube protrudes from the central hole of the rubber plug, and the lower end of the insulating tube passes through the lower port of the air inlet tube into the ZrO2 tube. _The lower end of the insulating tube is located above the liquid level of the molten electrolyte; the lower end of the insulating tube is fixed with Solid-state working electrode, the lower end of the solid-state working electrode is inserted into the molten electrolyte, the lower end of the solid-state working electrode lead passes through the central through hole of the insulating tube and is connected to the upper end of the solid-state working electrode, and the upper end of the solid-state working electrode lead extends out of the upper port of the insulating tube.

The ZrO ₂ tube is a solid electrolyte tube made by adding a dopant to the ZrO ₂ matrix and sintering it. The dopant is MgO or Y ₂ O ₃ , and the inner diameter of the ZrO ₂ tube is 5-20 mm. The wall thickness is 0.5~3mm.

The material of the auxiliary electrode and the reference electrode is platinum, the thickness of the platinum layer is 4-50 μm, and the porosity is 15-40%.

The material of the solid-state working electrode is one of the inert metals platinum, iridium and rhodium, and the diameter of the solid-state working electrode is 0.2-3 mm.

The material of the reference electrode lead is platinum; the material of the auxiliary electrode lead is platinum; the material of the solid working electrode lead is platinum.

When performing high-temperature measurement in the present invention, the electrolytic cell is placed in a constant temperature zone in a tubular high-temperature furnace, and air with a flow rate of 100 to 600 mL/min passes through the high-temperature furnace. Therefore, the outside surface of the electrolytic cell is in a flowing air environment. Introduce Ar or _N2 inert gas with a flow rate of _10-100mL /min into the intake pipe through the inert gas inlet to protect the molten electrolyte to be measured in the ZrO2 tube. When the furnace temperature reaches the measurement temperature, the three electrode clamps of the electrochemical analyzer respectively clamp the corresponding reference electrode lead, auxiliary electrode lead and solid-state working electrode lead of the electrolytic cell. After the electrolytic cell system is stabilized, the electrochemical behavior of electroactive oxides in the molten electrolyte can be studied by selecting the corresponding electrochemical testing technology.

Owing to adopting above-mentioned technical scheme, the present invention has following positive effect:

1) The present invention has simple structure and easy operation. As an excellent refractory material, ZrO ₂ tube has strong corrosion resistance, not only can be directly used as a container for molten electrolyte; more importantly: ZrO ₂ tube can be used as an auxiliary electrode and a reference electrode on the one hand. The matrix material for the integration of the electrolytic cell container, on the other hand, acts as a separator separating the auxiliary electrode from the solid-state working electrode in the molten electrolyte, which can not only effectively avoid the direct short circuit of electrons that may be generated between the auxiliary electrode and the solid-state working electrode, Moreover, it can prevent the adverse effect of the reaction participants on the auxiliary electrode on the solid-state working electrode. It can be seen that the adoption of the ZrO ₂ tube not only makes the structure of the electrolytic cell simple, but also makes the operation of the electrolytic cell easier.

2) The present invention has strong anti-interference ability. ZrO ₂ tube is an oxygen ion conductive solid electrolyte, which has selective permeability only for oxygen ions, can block the passage of electrons and other non-oxygen ions, and eliminate the interference of leakage current or other non-oxygen ions in the molten electrolyte.

3) The electrode of the present invention is convenient to prepare and has stable and reliable performance. The outer surface of the closed end of the ZrO ₂ tube is conveniently coated with platinum paste and sintered to prepare a porous reference electrode and an auxiliary electrode with stable performance. The area of the auxiliary electrode can easily meet the requirement of being much larger than the area of the solid-state working electrode, reducing the degree of polarization of the auxiliary electrode during electrochemical research. Put the porous reference electrode and auxiliary electrode at the closed end of the _ZrO2 tube in the environment of flowing air (stable oxygen partial pressure). Thermodynamic theoretical calculation; on the other hand, it can automatically form a reference electrode based _on ZrO2 tubes in an air environment with good reversibility, stability and reproducibility at high temperatures, which is beneficial to the electrochemical behavior of electroactive ions test research. The prepared reference electrode and auxiliary electrode can be easily separated from each other, avoiding the influence of the voltage drop caused by the current flowing in the electrolytic cell system and the change of the partial oxygen partial pressure of the auxiliary electrode outside the ZrO2 tube _on the performance of the reference electrode; in addition, The reference electrode on the outer surface of the ZrO ₂ tube is immediately above the auxiliary electrode, which can avoid direct erosion of the molten electrolyte on the inner surface of the ZrO ₂ tube matrix covered by the reference electrode. Therefore, compared with the two-electrode system electrolytic cell, the reference electrode in the air environment separated from the auxiliary electrode in the present invention is more beneficial to improve the stability and reliability of the test results of the electrochemical behavior of electroactive ions.

Therefore, the present invention has the characteristics of simple structure, easy operation, strong anti-interference ability and more stable and reliable test results. The invention is suitable for the research on the electrochemical behavior of the electroactive oxide in the molten electrolyte.

Description of drawings

Fig. 1 is a kind of structure diagram of the present invention.

detailed description

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, which is not intended to limit its protection scope.

Example 1

An electrolytic cell for studying the electrochemical behavior of electroactive oxides in molten electrolytes. As shown in Figure 1, the electrolytic cell includes a ZrO2 tube ₃ , a reference electrode 15, an auxiliary electrode 1 and a solid-state working electrode 2. The closed end of the ZrO ₂ tube 3 is filled with molten electrolyte, and the open end of the ZrO ₂ tube 3 is equipped with an alumina plug 5; the outer surface of the closed end of the ZrO ₂ tube 3 is surrounded and sintered from bottom to top with an auxiliary electrode 1 and a reference electrode. 15, the upper boundary of the auxiliary electrode 1 is flush with the molten electrolyte liquid level in the ZrO ₂ tube 3, and the reference electrode 15 is close to the upper boundary position of the auxiliary electrode 1; one end of the reference electrode lead 4 is fixedly connected with the reference electrode 15, and the auxiliary One end of the electrode lead 7 is fixedly connected to the auxiliary electrode 1 .

The lower half of the air intake pipe 13 is inserted into the ZrO pipe ₃ through the central hole of the alumina plug 5, and the central hole of the alumina plug 5 is provided with an exhaust hole 12, and the lower end of the air intake pipe 13 is located in the molten electrolyte solution. Above the surface, the upper port of the air intake pipe 13 is sealed and connected with the lower port of the T-shaped three-way pipe 10 through the rubber tube 6; The side port is an inert gas inlet 11.

The upper end of the insulating tube 14 stretches out from the central hole of the rubber plug 9, the lower end of the insulating tube 14 passes through the lower port of the air intake duct 13 into the ZrO2 tube ₃ , and the lower end of the insulating tube 14 is located above the liquid level of the molten electrolyte The lower end of the insulating tube 14 is fixed with a solid-state working electrode 2, the lower end of the solid-state working electrode 2 is inserted into the molten electrolyte, the lower end of the solid-state working electrode lead wire 8 passes through the central through hole of the insulating tube 14 and is connected to the upper end of the solid-state working electrode 2, and the solid-state The upper end of the working electrode lead wire 8 protrudes from the upper port of the insulating tube 14 .

The ZrO ₂ tube 3 is a solid electrolyte tube made by adding a dopant to the ZrO ₂ matrix and sintering it. The dopant is MgO, and the inner diameter of the ZrO ₂ tube 3 is 5-10 mm, and the wall thickness is 0.5 mm. ~1.5mm.

The auxiliary electrode 1 and the reference electrode 15 are made of platinum, the thickness of the platinum layer is 4-20 μm, and the porosity is 15-25%.

The material of the solid working electrode 2 is inert metal platinum, and the diameter of the solid working electrode 2 is 2-3mm.

The material of the reference electrode lead 4 is platinum; the material of the auxiliary electrode lead 7 is platinum; the material of the solid working electrode lead 8 is platinum.

Example 2

An electrolytic cell for studying the electrochemical behavior of electroactive oxides in molten electrolytes. Except following technical parameter, all the other are with embodiment 1:

The dopant is Y ₂ O ₃ , the inner diameter of the ZrO ₂ tube 3 is 10-15 mm, and the wall thickness is 1.5-2.5 mm.

The materials of the auxiliary electrode 1 and the reference electrode 15 are both platinum, the thickness of the platinum layer is 20-35 μm, and the porosity is 25-35%.

The material of the solid working electrode 2 is inert metal iridium, and the diameter of the solid working electrode 2 is 1-2mm.

Example 3

An electrolytic cell for studying the electrochemical behavior of electroactive oxides in molten electrolytes. Except following technical parameter, all the other are with embodiment 1:

The dopant is Y ₂ O ₃ , the inner diameter of the ZrO ₂ tube 3 is 15-20 mm, and the wall thickness is 2-3 mm.

The auxiliary electrode 1 and the reference electrode 15 are made of platinum, the thickness of the platinum layer is 35-50 μm, and the porosity is 30-40%.

The material of the solid working electrode 2 is inert metal rhodium, and the diameter of the solid working electrode 2 is 0.2-1.2 mm.

When performing high-temperature measurement in this specific embodiment, the electrolytic cell is placed in a constant temperature zone in a tubular high-temperature furnace, and air with a flow rate of 100-600 mL/min passes through the high-temperature furnace. Therefore, the outside surface of the electrolytic cell is in a flowing air environment. Introduce Ar or _N2 inert gas with a flow rate of 10-100mL/min into the gas inlet tube 13 through the inert gas inlet 11 to protect the molten electrolyte to be measured inside the ZrO2 tube ₃ . When the furnace temperature reaches the measurement temperature, the three electrode clamps of the electrochemical analyzer respectively clamp the reference electrode lead 4, auxiliary electrode lead 7 and solid-state working electrode lead 8 corresponding to the electrolytic cell. After the electrolytic cell system is stabilized, the electrochemical behavior of electroactive oxides in the molten electrolyte can be studied by selecting the corresponding electrochemical testing technology. Such as:

Dissolve iron oxide in SiO ₂ -CaO-MgO-Al ₂ O ₃ molten electrolyte, use this electrolytic cell, select the cyclic voltammetry test technique on the electrochemical analyzer, and use platinum wire as the solid-state working electrode under the condition of 1450oC 2 , to study the electrochemical behavior of iron oxides in SiO ₂ -CaO-MgO-Al ₂ O ₃ molten electrolytes. Electroactive iron oxide exists as Fe ³⁺ , Fe ²⁺ , O ^2- plasma in molten electrolyte. When scanning negatively from the starting point, Fe ³⁺ and Fe ²⁺ in the slag diffuse to the surface of the solid working electrode 2; O ^2- in the molten electrolyte diffuses to the interface of the molten electrolyte/ZrO ₂ tube 3 and passes through the ZrO ₂ tube 3 , reaching the auxiliary electrode 1 interface of the ZrO ₂ tube 3 . After the scanning potential reaches the reduction potential of Fe ³⁺ and Fe ²⁺ , Fe ³⁺ and Fe ²⁺ are reduced successively on the surface of the solid-state working electrode 2, and two reduction peaks appear on the cyclic voltammetry curve; The O 2- passing through the ZrO ₂ tube ₃ enters the air after being oxidized to O ² at the auxiliary electrode 1. During retrace, multiple oxidation peaks appeared successively on the cyclic voltammetry curve at different scan rates. At the same time, on the auxiliary electrode 1 outside the ZrO ₂ tube 3, O ₂ in the air is reduced to O ^2- : O ₂ +4e=2O ^2- , and then O ^2- enters the molten electrolyte through the ZrO ₂ tube 3 . After the active metal on the solid working electrode 2 is oxidized, the O 2 − diffused to the surface of the solid working electrode ² is oxidized, and O ₂ gas is precipitated. Due to the continuous release of _O2 bubbles on the solid-state working electrode 2 in the molten electrolyte, the cyclic voltammetry curve exhibits a sawtooth-shaped small fluctuation. According to the measured cyclic voltammetry curves, the electrochemical behavior of electroactive iron oxides in the molten electrolyte can be analyzed.

Owing to adopting above-mentioned technical scheme, this specific embodiment has following positive effect:

1) This embodiment has simple structure and easy operation. As an excellent refractory material, ZrO ₂ tube 3 has strong corrosion resistance, not only can be directly used as a container for molten electrolyte _; The matrix material that the ratio electrode 15 is integrated with the electrolytic cell container, on the other hand, acts as a separator that separates the auxiliary electrode 1 from the solid-state working electrode 2 in the molten electrolyte, which can not only effectively avoid the gap between the auxiliary electrode 1 and the solid-state working electrode 2. The electrons that may be generated between them are directly short-circuited, and the adverse effects of the reaction participants on the auxiliary electrode 1 on the solid-state working electrode 2 can be prevented. It can be seen that the adoption of the ZrO ₂ tube 3 not only makes the structure of the electrolytic cell simple, but also makes the operation of the electrolytic cell easier.

2) This embodiment has strong anti-interference ability. ZrO ₂ tube 3, as a solid electrolyte conducting oxygen ions, has selective permeability only for oxygen ions, can block the passage of electrons and other non-oxygen ions, and eliminate the interference of leakage current or other non-oxygen ions in the molten electrolyte.

3) The electrode of this specific embodiment is easy to prepare and has stable and reliable performance. The outer surface of the closed end of the ZrO ₂ tube 3 is conveniently coated with platinum paste and sintered to prepare a porous reference electrode 15 and an auxiliary electrode 1 with stable performance. The area of the auxiliary electrode 1 can conveniently meet the requirement that the area of the auxiliary electrode 1 is much larger than that of the solid-state working electrode 2, so as to reduce the degree of polarization of the auxiliary electrode 1 during electrochemical research. Place the porous reference electrode 15 and the auxiliary electrode 1 at the closed end of the ZrO ₂ tube 3 in a flowing air (stable oxygen partial pressure) environment. On the one hand, the partial pressure of the participating substance oxygen that reacts on the auxiliary electrode 1 can be fixed at 21kPa , it is beneficial to carry out relevant thermodynamic theoretical calculations; on the other hand, it can automatically form a reference electrode 15 based on ZrO ₂ tube 3 in an air environment with good reversibility, stability and reproducibility at high temperature, which is beneficial to carry out Test studies on the electrochemical behavior of electroactive ions. The prepared reference electrode 15 and auxiliary electrode 1 can be easily separated from each other, avoiding the voltage drop caused by the current flowing in the electrolytic cell system and the change of the partial oxygen partial pressure of the auxiliary electrode 1 outside the ZrO2 tube ₃ affecting the performance of the reference electrode 15. In addition, the reference electrode 15 on the outer surface of the ZrO ₂ tube 3 is close to the upper position of the auxiliary electrode 1, which can avoid direct erosion of the ZrO ₂ tube 3 matrix inner surface covered by the reference electrode 15 by the molten electrolyte. Therefore, compared with the two-electrode system electrolytic cell, the reference electrode 15 in the air environment separated from the auxiliary electrode 1 in this specific embodiment is more beneficial to improve the stability and reliability of the test results of the electrochemical behavior of electroactive ions.

Therefore, this embodiment has the characteristics of simple structure, easy operation, strong anti-interference ability and more stable and reliable test results. This specific embodiment is applicable to the research on the electrochemical behavior of electroactive oxides in molten electrolytes.

Claims (5)

1. for studying an electrolytic cell for the electroactive oxide electrochemical behavior of fused electrolyte, it is characterized in that described electricityXie Chi comprises ZrO₂Pipe (3), reference electrode (15), auxiliary electrode (1) and solid-state working electrode (2); ZrO₂In pipe (3) blind endFused electrolyte is housed, ZrO₂The openend port of pipe (3) is equipped with aluminium oxide plug (5); At ZrO₂The outer surface of pipe (3) blind endThere are auxiliary electrode (1) and reference electrode (15), coboundary and the ZrO of auxiliary electrode (1) around sintering successively from down to up₂Pipe(3) the fused electrolyte liquid level in is concordant, reference electrode (15) next-door neighbour auxiliary electrode (1) position, coboundary; Reference electrode lead-in wire(4) one end is fixedly connected with reference electrode (15), and one end of auxiliary electrode lead-in wire (7) is fixedly connected with auxiliary electrode (1);

The Lower Half of air inlet siphunculus (13) is inserted ZrO by the centre bore of aluminium oxide plug (5)₂In pipe (3), in aluminium oxide plug (5)Heart hole is other is provided with steam vent (12), and the lower end of air inlet siphunculus (13) is positioned at the top of fused electrolyte liquid level, air inlet siphunculus (13)Upper port be tightly connected by the lower port of rubber tube (6) and T-shaped three-way pipe (10); T-shaped three-way pipe (10) upper end port is establishedHave rubber stopper (9), the other port of T-shaped three-way pipe (10) is inert gas air inlet (11);

Stretch out from the centre bore of rubber stopper (9) upper end of insulation tube (14), and the lower end of insulation tube (14) is from air inlet siphunculus (13)Lower port passes to ZrO₂In pipe (3), the lower end of insulation tube (14) is positioned at the top of fused electrolyte liquid level; Insulation tube (14)Lower end is fixed with solid-state working electrode (2), and insert in fused electrolyte the lower end of solid-state working electrode (2), solid-state working electrodeThe lower end of lead-in wire (8) is connected with the upper end of solid-state working electrode (2) through the central through hole of insulation tube (14), solid-state working electrodeInsulation tube (14) upper port is stretched out in the upper end of lead-in wire (8).

2. as claimed in claim 1 for studying the electrolytic cell of the electroactive oxide electrochemical behavior of fused electrolyte, itsBe characterised in that described ZrO₂Pipe (3) is at ZrO₂In matrix, add the solid electrolyte tube that sintering is made after adulterant, describedAdulterant is MgO or is Y₂O₃，ZrO₂The internal diameter of pipe (3) is 5 ~ 20mm, and wall thickness is 0.5 ~ 3mm.

3. as claimed in claim 1 for studying the electrolytic cell of the electroactive oxide electrochemical behavior of fused electrolyte, itsBe characterised in that described auxiliary electrode (1) and the material of reference electrode (15) are platinum, the bed thickness of platinum is 4 ~ 50 μ m, holeDegree is 15 ~ 40%.

4. as claimed in claim 1 for studying the electrolytic cell of the electroactive oxide electrochemical behavior of fused electrolyte, itsThe material that is characterised in that described solid-state working electrode (2) is the one in inert metal platinum, iridium, rhodium, solid-state working electrode (2)Diameter be 0.2 ~ 3mm.

5. as claimed in claim 1 for studying the electrolytic cell of the electroactive oxide electrochemical behavior of fused electrolyte, itsThe material that is characterised in that described reference electrode lead-in wire (4) is platinum; The material of described auxiliary electrode lead-in wire (7) is platinum; InstituteThe material of stating solid-state working electrode lead-in wire (8) is platinum.