Effect of Oxygen Implantation on the Electrochemical Properties of Palladium

Abstract

AbstractThe electrochemical properties of O+-implanted Pd measured by cyclic voltammetry in a 0.25 mol dm-3 H2SO4 solution were investigated in relation to their composition and structure. Implantation of 16O+ was performed with doses between 1O17 and 1O18 ions cm-2 at 150 keV, and at nearly room temperature. SIMS, ERD combined with RBS, and XRD were used to analyze the composition depth profile and structure of O+-implanted Pd surface layers. The H atoms were accumulated with a gaussian distribution and carbon materials containing the solid solution of PdCx (x=0.13-0.15) were also formed in the near surface layers during O+-implantation. The distribution of implanted oxygen changed from gaussian to trapezoidal as the dose increased, accompanied by the crystal growth of Pd(OH)2, and simultaneously, the amount of accumulated H atoms increased. The voltammetric measurements revealed that with an increase in the dose, the hydrogen absorption was suppressed at the early stage of sweep cycles, and at the final stage, the redox reaction of both hydrogen and Pd was activated. From these results, we propose that the carbon materials containing the PdCx formed during O+-implantation suppress the hydrogen absorption, and the metallic Pd like a Pd-black formed by the reduction of Pd(OH)2 during voltammetric measurements causes the electrochemical activation of O+-implanted Pd.