Spontaneous deposition of Pd onto Fe–Cr–Al alloys

The spontaneous deposition of Pd onto Fecralloy sheets and foams was studied. Pd deposits were obtained by immersion of Fecralloy samples in mildly acid, deaerated PdCl2 solutions, at open circuit. Pd displaced all alloy elements and deposited onto the alloy which was initially coated by an oxides film and underwent transpassive dissolution. The Pd loading and the Pd surface area were determined as a function of experimental conditions, like the nature of the Fecralloy sample (sheets or foams of variable grade), the concentration of the PdCl2 solution and the duration of the deposition. The results were compared to those obtained by depositing Pd onto Ni foams, with the same procedure. The Pd deposition rates were not much different on Fecralloy and Ni, but the Pd surface area per unit Pd mass was significantly higher for Ni than for Fecralloy. The Pd deposit morphology was influenced by the presence of passive oxides on the Fecralloy surface. The catalytic activity in methanol anodic oxidation depended only on the Pd surface area, irrespective of the nature of the support (Ni or Fecralloy).