Counter Electrodes

Q&A. 백금 또는 그라파이트 상대 전극 선택 요령은?

Let’s first review the purpose of the counter electrode. The counter electrode completes the circuit for the potentiostat and drives current through the electrochemical cell. As such, the counter electrode has to have a large area than the working electrode and be sufficiently active at passing current through the electrochemical cell, while still being “inert” to not affect the electrochemistry at the working electrode.

With that said, the platinum counter electrode has a smaller area than the graphite rod and is more expensive. However, the platinum counter electrode is more “active” than the graphite rod, meaning that it intrinsically passes current more easily than the graphite rod electrode. Some researchers might need to add a “sacrificial agent” to the counter electrode if there is nothing for the counter electrode to oxidize or reduce. Platinum is so good at oxidizing and reducing that a sacrificial agent is rarely needed, but it might be needed for a graphite rod (depends on the system). Because it requires more voltage to drive a current through the graphite rod, the user would benefit from using a potentiostat with a large compliance voltage. Compliance voltage is rarely an issue, but it can be an issue with some customer setups

The last consideration is platinum or carbon contamination. If the customer is doing CO2 reduction research, using a graphite rod could be problematic because the graphite could leech out of counter electrode and produce false positives. However, the same argument could be made for platinum, and that platinum from the counter electrode is getting on the working electrode and contaminating your system.