Effects of bulk modification by Pd on electrochemical properties of MgNi

An amorphous MgNi alloy was prepared by ball-milling of Mg₂Ni and Ni with 10 mol% of Pd for 80 h, and effects of the bulk modification by Pd on the electrochemical properties of amorphous MgNi were investigated by using a conventional two-electrode system. It was found through X-ray diffraction (XRD) and high-resolution transmission electron microscope (HRTEM) analyses that Pd dissolved uniformly into the bulk of MgNi during the ball milling without affecting the amorphous structure of MgNi. As a result, the cycle life of Pd-modified MgNi in alkaline solution was significantly improved. HRTEM and XRD observations showed that a dense layer of fine grains of Mg(OH)₂ covered over the surface of unmodified MgNi powder after the immersion in alkaline electrolyte solution, whereas no appreciable extent of Mg(OH) ₂ formation was observed on the Pd-modified MgNi powder. These observations demonstrate that the Pd bulk modification is very effective to suppress the formation of Mg(OH)₂ layer and hence gives rise to the remarkable improvement of the cycle life of the electrode.