Platinum or Carbon as counter electrode material is preferred because both require low maintenance and don’t easily get oxidized or reduced.
Platinum:
Platinum, due to its inertness and electrical conductivity, is found to be one of the best counter-electrode materials. Platinum electrodes are available in different forms such as – mesh, foil, wire, and tip. Based on experimental requirements, different forms of platinum electrodes are employed and a mesh kind of platinum electrode is widely used due to its high surface area and porous nature.
Limitations:
- Cost-effective
Carbon (graphite rods):
- Graphite rods are more affordable than platinum, have higher corrosion resistance, are chemically inert in a wide range of conditions, and have better electrical conductivity.
- These materials (carbon or graphite) are employed as counter electrodes in screen printed electrodes (SPE) because of their low cost, electrical conductivity, and environmental friendliness.
Limitations:
- Limited potential range compared to platinum.
- Less inert when compared to platinum electrode
- It cannot be used in very acidic and oxidizing environments.
- It has a shorter lifespan.