GLASSY CARBON MODIFIED ELECTRODES WITH LAYERED DOUBLE HYDROXIDES FOR THE OXYGEN EVOLUTION REACTION

Glassy carbon electrodes (GCE) were modified with a thin film of Ni/Al and Ni/Fe Layered Double Hydroxides (LDHs). The LDHs were chemically synthesized, by the double-microemulsion method according to literature data1. That modified electrodes were found to be active towards the oxygen evolution reaction (OER). The OER activity of LDHs modified electrodes was investigated in 0,1 M NaOH, at a slow scan rate of 5 mV/s, between 0 V and the OER onset potential (Ag/AgCl/3 M was used as reference electrode). During the measurements the working electrode was rotating at 1600 rpm to remove the generated oxygen bubbles from it surface. The electrochemical characterization of the Ni/Al and Ni/Fe-LDHs evidenced that the OER onset potential of those modified electrodes occurred respectively at +0.55 V and +0.53 V, showing a considerably reduced potential, compared to the values recorded in the same conditions with the bare GCE or GCE modified with a film of not redox active Mg/Al and Mg/Fe-LDHs (onset of OER current at ~1.20 V). A similar behaviour to the chemically synthesized active catalysts, was observed for the ones electrochemically synthesized from a solution of Ni(NO3)2 and Fe(NO3)3 or Al(NO3)3 (molar ratio 3:1), by applying an anodic potential of -0,9 V for 90 seconds. Furthermore the active LDHs exhibited a good stability in alkaline solution, since the chronopotentiometry curves, recorded applying a current density of 2,5 mA/cm2 for five minutes, showed that the catalysts had a nearly constant operating potential.