EN - Page 10
Working electrode (6)
The working electrode is placed between two seals. To prevent the seals from slipping,
there are 3 PTFE pins (7). For fitting between these pins, the sample must be cut to the
dimensions 30 mm x 50 mm.
If you want to use electrodes of other geometries, you can simply remove these PTFE
pins.
If the working electrode is a gas diffusion electrode with a non-conductive gas diffusion
layer such as porous PTFE, then the PTFE film must be removed about 1 cm from the
edge so that the sample can be contacted there. The catalyst mass can also be removed
carefully on this piece. This prevents air from entering the sample from the outside and is
especially important for measurements on nickel hydrogen electrodes.
Contact working electrode (8)
Two 4 mm gold-plated multilam plugs press onto the working electrode from the rear. If
the contact is not sufficient, the multilam plugs can be tightened with a socket spanner.
Make sure that these plugs are clean. Replace these plugs if the gold-plated layer no
longer looks sufficiently good. This also applies to all measuring cables.
Gas supply (9)
For measurements on gas diffusion electrodes, these must be supplied with gas. Here, it
is done via the working electrode holder, made of transparent plastic so that the
electrode can be observed. It has two connections: the gas inlet at the top and the gas
outlet at the bottom. If liquid gets through the electrodes, it can be removed with the gas
flow.
Gas bubbles (10)
There cannot be any electrolyte where the gas bubbles stick to the electrode. Gas
bubbles can block the reaction surface. Local elements can form. Gaskatel test cells
have an additional opening through which any gas bubbles that form are removed in a
controlled manner.
Crevice corrosion (11)
If the sample is not properly sealed, an electrochemical reaction may take place
underneath the sealing or even outside of the active area. A proper sealing is essential.
Oxygen may only enter in a controlled manner.
Flat sealings have proven successful with very noble materials, thin samples or gas
diffusion electrodes.
O-ring seals should be used with base materials such as steel, aluminium, etc.
The measuring cells are therefore supplied with the appropriate O-rings and appropriately
cut silicone flat sealings.
