Synthesis of Ca2Mn3O8 films and their electrochemical studies for the oxygen evolution reaction (OER) of water

► Ca2Mn3O8 active catalyst for water oxidation and organic matter decomposition. ► Ca2Mn3O8 layer structure. ► Evaluation of Ca2Mn3O8 as powder and films. ► Differential electrochemical mass spectroscopy to corroborate oxygen and carbon dioxide evolution.