Reference half-cell and electrochemical sensor with the reference half-cell
A reference half-cell for application in an electrochemical sensor, comprising a housing, in which a chamber containing a reference electrolyte is formed, wherein the reference electrolyte ( 5, 105 ) is in contact with a medium surrounding the housing via a liquid junction arranged in a wall of the housing, wherein the liquid junction comprises a porous diaphragm, especially a porous ceramic diaphragm, and wherein the diaphragm has, at least partially, a coating, which comprises at least one metal.
1. A method for manufacturing a reference half-cell, wherein the reference half-cell comprises:
a housing in which a chamber containing a reference electrolyte is formed, wherein the reference electrolyte is in contact with a medium surrounding the housing via a liquid junction disposed in a wall of the housing wherein
the liquid junction comprises a diaphragm of porous media,
the diaphragm having an outer surface defining a volume, the volume including a plurality of pores within the media, each of the plurality of pores having an inner surface,
the diaphragm further including a coating distributed on the inner surfaces of the plurality of pores and on the outer surface, such that the coating at least partially covers the inner surfaces and the outer surface, wherein the coating includes at least one metal, the method comprising the steps of:
providing a porous diaphragm in a housing wall of a housing;
forming a chamber for accommodating a reference electrolyte in the housing of the reference half-cell; and
coating the diaphragm with a coating comprising at least one metal,
wherein the step of coating comprises contacting the diaphragm with a solution containing the at least one metal in the form of a metal salt or in the form of nano particles and depositing from the solution the coating within the pores and on the surface of the diaphragm.
2. The method as claimed in claim 1 , wherein prior to providing the porous diaphragm in the housing wall, the method further comprises the following steps:
providing a porous stock;
contacting the stock with a solution containing the at least one metal in the form of a metal salt or in the form of nano particles;
depositing from the solution the coating within the pores and on the surface of the porous stock; and
isolating a segment of the coated porous stock for forming the diaphragm.
3. The method as claimed in claim 2 , wherein
the depositing of the coating from the solution containing the metal in the form of a metal salt is performed currentlessly or galvanically.
4. The method as claimed in claim 2 , wherein
the depositing of the coating from the solution containing the metal in the form of a metal salt or in the form of nano particles is performed by thermal treatment of the stock or diaphragm supplied with the solution.
5. The method as claimed in claim 2 , wherein
before depositing the coating comprising at least one metal, a layer promoting adhesion of the metal-comprising coating is applied on the stock.
6. The method as claimed in claim 2 ,
wherein the porous stock comprises a plurality of pores and
wherein the step of contacting the stock with the solution comprises drawing the liquid through the pores before the metal is deposited within the pores and on the surface of the stock.
7. The method as claimed in claim 1 ,
wherein the step of contacting the diaphragm with a solution containing the at least one metal comprises
drawing the liquid into the pores of the diaphragm and forming the coating also within the pores.
8. The method as claimed in claim 1 , wherein the porous media is one of the group of zirconium dioxide, ceramic, glass, and Teflon.