CO electroreduction favors carbon isotope C over C and facilitates isotope separation.

We discovered that CO electroreduction strongly favors the conversion of the dominant isotope of carbon (C) and discriminates against the less abundant, stable carbon C isotope. Both absorption of CO in the alkaline electrolyte and CO electrochemical reduction favor the lighter isotopologue. As a result, the stream of unreacted CO leaving the electrolyzer has an increased C content, and the depletion of C in the product is several times greater than that of photosynthesis.