Improvement in electrochemical performances of Mn(NiCoMnAl)5 electrodes by surface modification

All metal elements an the surface of the hydrogen storage alloys exist in oxide slate. The ox ide layer on the surface of alloys affects the electrochemical performances of metal hydride (MH) electrodes. The surface of MH electrode was modified by immersing in 0.05 mol/L KBH4 + 6 mol/L KOH or 0.2 mol/L NaH2PO2 + 6 mol/L KOH solution. It is found that their electrochemical properties such as discharge capacity, activation and cyclic stability are apparently improved. The effects of the mentioned surface modifications on the activity of electrochemical reaction were investigated by means of cyclic voltammetry (CV) and electrochemical impedance spectra (EIS). it is found that the surface modifications considerably improve the electrochemical activity and decrease the activation enthalpy of electrode reaction.