Studies on the influence of palladium coatings on the electrochemical and structural properties of a metal hydride alloy

Electroless palladium deposition was made on the surface of LaNi4.7Sn0.3 metal hydride particles with the aim of studying the influence on the charge/discharge performance of this alloy. The palladium layer was produced by chemical replacement of a copper film deposited on the alloy and its structure was studied by X-ray absorption spectroscopy. The residual copper layer remaining on the alloy surface after palladium deposition was mainly composed of metallic nanometric particles. Ex situ X-ray absorption near-edge structure (XANES) at the Ni K edge indicated that the Pd/Cu layer may protect the Ni atoms against corrosion during the charge/discharge cycles. XANES also indicates that the palladium layer presents the same unit cell characteristics of the bulk Pd in a foil. The electrode prepared with the coated alloy presented lower charge/discharge overpotentials as well as lower charge transfer resistance as verified by electrochemical impedance spectroscopy.