EFFECT OF COBALT ADDITION ON THE PERFORMANCE OF TITANIUM-BASED HYDROGEN-STORAGE ELECTRODES

The influence of cobalt addition on the performance of a Ti2Ni hydroge n-storage alloy is examined. The cobalt addition is confirmed by energ y dispersive spectroscopy compositional analysis. X-ray diffraction (X RD) results reveal that cobalt partially substitutes the nickel in the Ti2Ni alloy. Charge/discharge cycle measurements show that the specif ic capacity of Ti2Ni electrodes increases with cobalt addition, reache s a maximum at a cobalt content of 0.67 at.% (Ti2Ni0.98Co0.02), and th en falls with further addition. The cycle life of Ti2Ni electrodes inc reases significantly with cobalt addition. Scanning electron microscop y analysis reveals that cobalt is effective in reducing the disintegra tion of the Ti2Ni hydrogen-storage alloy powder, while XRD analysis sh ows that cobalt restricts the oxidation of the Ti2Ni hydrogen-storage alloy. By contrast, the addition of cobalt does not inhibit the format ion of the irreversible Ti2NiH0.5 hydride phase.