Electrochemical and X-ray absorption spectroscopy studies of copper coatings on a hydrogen storage alloy

Electroless copper deposits were made on the surface of LaNi4.7Sn0.3 particles with the aim of studying the influence on the charge/discharge performance of this metal hydride alloy. Cu layers were produced using formaldehyde and hydrogen as reducing agents and the near-range order and composition investigated as a function of deposition method by X-ray absorption spectroscopy. The electroless layer deposited using formaldehyde was shown to be mainly in the metallic state (Cu0). The copper layer prepared using hydrogen resulted in a mixed phase formed by metallic and oxidized copper species. Results also indicated that the copper layer protects the Ni atoms against corrosion, but this does not help in capacity retention during the charge/discharge cycling of the alloy. The electrode coated with the hydrogen reduced copper layer had lower discharge overpotentials relative to the uncoated electrode, implying an increase in the exchange current density for the process.