Study of a tin-free activation process for electroless nickel deposition on polyurethane foam and feasibility for catalyst preparation

Abstract

A tin-free activation process has been studied for electroless nickel plating on polyurethane (PU) foam. The effect of HCl concentration (2-6 molar), PdCl2 concentration (0.2-1.8 g/l), and the type of reducing agents (sodium hypophosphite and hydrazine) on the properties of the activated surface and the deposition of Ni were investigated by SEM, EDX, XPS, and Instron. More uniform coating and higher amount of Ni deposit were obtained with higher amount of PdCl₂ during activation. The morphology and mechanical properties of the Ni/PU foam prepared by electroless deposition with and without SnCl₂ activation were similar. In addition, for the non-SnCl₂ activation, the nickel electroless bath was not decomposed and can be reused.The characteristics and catalytic properties of Pd/TiO₂ catalysts prepared by electroless deposition method with and without SnCl₂ activation were investigated. The particle size and morphology Pd particles dispersed on TiO₂ powder were significantly dependent on the activation process. The non-Sn activation resulted in much larger Pd particle/cluster size than those of the electroless SnCl₂. The catalyst performances in the liquid-phase hydrogenation of 3-hexyne-1-ol to cis-hexene-1-ol were improved in the order: Pd/TiO₂ non-Sn > Pd/TiO₂ Sn > Pd/TiO₂ impregnation. It is suggested that electroless deposition resulted in lower surface imperfections of the Pd/TiO₂ catalysts than the conventional impregnation technique.