The Counter Electrode (CE) in SPE is made up of carbon ink because of the low cost and inertness. The main purpose of the CE is to maintain electrical neutrality and it helps to complete the circuit.
The Working Electrode (WE) is usually made up of silver, gold, or other metals inks based on the application or target analyte as it must be sensitive to analyte concentration.
Silver and silver chloride mixture ink is commonly used to print Reference Electrodes (RE) because of their low cost and easy availability. These silver/silver chloride inks are good conductors and it is very stable in various electrochemical conditions.