Ultraweak emission of the Eu(III) ions in cathodic generated electrochemiluminescence

► We studied electrochemiluminescence (ECL) of systems generating weak photon emission.► We examined ECL systems containing europium salts, and co-reactants: H2O2 and K2S2O8.► The source of exciting Eu3+ is the emission from the Al/Al2O3 electrode surface.► The Eu(III)-specific emission is produced via proposed mechanisms in the ECL process.