Cyclic voltammetric behavior of Pd-Pt-Rh ternary alloys

The electrochemical behavior of Pd - Pt - Rh alloys has been investigated using cyclic voltammetry ( CV). The alloys were prepared by electrochemical codeposition as limited volume electrodes ( less than 1 mum in thickness). The morphology of the alloy surface and bulk compositions were examined by the SEM/EDAX method. Surface oxides generation ( oxygen adsorption) and oxides reduction ( oxygen desorption) currents together with hydrogen adsorption and hydrogen absorption signals can be distinguished on CV curves. During potential cycling through the full hydrogen oxygen potential range Rh and Pd are preferentially dissolved, which is reflected in a dramatic transformation in the voltammogram shape. The composition changes involve not only the surface but also some atomic layers beneath the surface.