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