Pd Modified MmNi50.6Co10.2Mn5.4Al1.2 Alloy as the Catalyst of NaBH4 Electrooxidation.

A Pd-modified hydrogen storage alloy was investigated as the anode electrocatalyst of direct borohydride fuel cell. The modification of the MmNi_50.6 Co_10.2 Mn_5.4 Al_1.2 hydrogen storage alloy with Pd was carried out by a self-reduction reaction method. The morphology and the distribution of Pd on the surface of the alloy were observed by scanning electron microscope and energy dispersive X-ray spectrometer. It was found that Pd particles uniformly distributed on the alloy surface and the content of Pd was 0.64 wt.%. The catalytic activity of the Pd-modified hydrogen storage alloy for NaBH₄ electrooxidation was evaluated by cyclic voltammetry and chronoamperometry measurements. Results showed that Pd modification significantly enhanced the catalytic activity of the hydrogen storage alloy. In the 1.0 mol dm^-3 NaOH+ 0.1 mol dm^-3 NaBH₄ solution, the stabilized current density at -0.7 V was 34 and 22 mA cm^-2 for the pristine and the Pd-modified alloy, respectively. The utilization efficiency of NaBH₄ on the Pd-modified alloy catalyst reached 45%, which is higher than that on the pristine alloy (30%). The number of electrons released by BH₄^- electrooxidation on Pd-modified alloy was found to be close four. [ABSTRACT FROM AUTHOR]