Improved Electrochemical Kinetic Performances of La-Mg-Ni-based Hydrogen Storage Alloy Modified by Ni-Polypyrrole Complex Surface Treatment

In order to improve the electrochemical kinetic performances of La-Mg-Ni-based alloy, complex surface modification of Ni with excellent catalytic activity and conducting polymer polypyrrole(PPy) was performed via electroless plating method. FESEM images revealed that the complex Ni-PPy treatment resulted in more micropores at the alloy surface, with Ni particles and cotton fiber-shape PPy microspheres attached. Both the larger surface area induced by the micropore and the higher catalytic activity and conductivity on account of the dispersed Ni particles/PPy microspheres promoted the electrode reaction, thereby increasing the discharge capacity of the modified alloy electrode. Electrochemical impedance spectroscopy(EIS) and linear polarization results showed that the Ni-PPy treatment decreased the charge-transfer resistance and increased the exchange current density greatly, far more than the single-component Ni or PPy treatment. Consequently, a notable improvement in high rate dischargeability(HRD) was observed, and at a high discharge current density of 1800 mA/g, the HRD of the modified electrode increased by 10.4% compared with that of the bare electrode.