SURFACE-ANALYSIS OF A TI-NI-B HYDROGEN STORAGE ELECTRODE

A Ti-Ni-B hydrogen storage alloy electrode was prepared by powder meta llurgy. Using X-ray photoelectron spectroscopy (XPS) and Auger electro n spectroscopy (AES), the chemical state and composition of the electr ode surface were analysed before and after electrochemical charge-disc harge cycles. The constituent elements on the surface existed as oxide s or hydroxides. Titanium and boron segregated to the surface, especia lly boron. At a depth of about 300 angstrom, the alloy bulk concentrat ion was reached. The oxidized surface layer became thicker and the seg regation of titanium and boron to the surface gradually increased duri ng cycling. The preferential segregation to the surface was probably i nduced by chemical reaction. The oxidation and segregation of titanium were main reasons leading to the decrease in capacity of the electrod e.