Surface analysis of a TiNiB hydrogen storage electrode

Abstract A TiNiB hydrogen storage alloy electrode was prepared by powder metallurgy. Using X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES), the chemical state and composition of the electrode surface were analysed before and after electrochemical charge-discharge cycles. The constituent elements on the surface existed as oxides or hydroxides. Titanium and boron segregated to the surface, especially boron. At a depth of about 300 A, the alloy bulk concentration was reached. The oxidized surface layer became thicker and the segregation of titanium and boron to the surface gradually increased during cycling. The preferential segregation to the surface was probably induced by chemical reaction. The oxidation and segregation of titanium were main reasons leading to the decrease in capacity of the electrode.