How to Define Anode and Cathode

Here's a look at the difference between the anode and cathode of a cell or battery and how you can remember which is which.

Flow of Current

The anode and cathode are defined by the flow of current. In the general sense, current refers to any movement of electrical charge. However, you should keep in mind the convention that current direction is according to where a positive charge would move, not a negative charge. So, if electrons do the actual moving in a cell, then current runs the opposite direction. Why is it defined this way? Who knows, but that's the standard. Current flows in the same direction as positive charge carriers, for example, when positive ions or protons carry the charge. Current flows opposite the direction of negative charge carriers, such as electrons in metals.

Cathode

• The cathode is the negatively charged electrode.
• The cathode attracts cations or positive charge.
• The cathode is the source of electrons or an electron donor. It may accept positive charge.
• Because the cathode may generate electrons, which typically are the electrical species doing the actual movement, it may be said that cathodes generate charge or that current moves from the cathode to the anode. This can be confusing, because the direction of current would be defined by the way a positive charge would move. Just remember, any movement of charged particles is current.

Anode

• The anode is the positively charged electrode.
• The anode attracts electrons or anions.
• The anode may be a source of positive charge or an electron acceptor.

Cathode and Anode

Remember, charge can flow either from positive to negative or from negative to positive! Because of this, the anode could be positively charged or negatively charged, depending on the situation. The same is true for the cathode.

Sources

• Durst, R.; Baumner, A.; Murray, R.; Buck, R.; Andrieux, C. (1997) "Chemically modified electrodes: Recommended terminology and definitions." IUPAC. pp 1317–1323.
• Ross, S. (1961). "Faraday consults the scholars: the origins of the terms of electrochemistry." Notes and Records of the Royal Society of London. 16: 187–220. doi:10.1098/rsnr.1961.0038