At this interface the oxygen ion transfers its charge to the anode, combines with another oxygen atom to form oxygen (O2), and diffuses out of the anode. The net reaction is thus 2CO 2 ⟶ {\displaystyle \longrightarrow } 2CO + O 2. Inert gases such as N 2 and Ar are not separated from the feed, but returned to the atmosphere with the carbon monoxide (CO) and unused CO2.[13]