The role of carbonate in electro-catalytic water oxidation by using Ni(1,4,8,11-tetraazacyclotetradecane)²⁺

NiL_i²⁺ are good electro-catalysts for water oxidation in phosphate or carbonate buffers. The results point out that the active oxidizing agents are L(X)Ni^IVOH^{4-(3-n+1)/(2-n+1)}, where X = PO₄H_n^(3-n)- or CO₃H_n^(2-n)- formed from LNi^IVX₂via a mechanism involving an acid catalyzed O-P or O-C bond heterolysis. Carbonate behaves differently from phosphate as it is a non-innocent ligand and it can be oxidized.