Pd-Ni alloy nanoparticle doped mesoporous SiO₂ film: the sacrificial role of Ni to resist Pd-oxidation in the C-C coupling reaction.

A Pd-Ni alloy nanoparticle (NP) doped mesoporous SiO2 film was synthesized using a one pot inorganic-organic sol-gel process in the presence of structure director P123. Pure Pd and Ni NP containing films were also synthesized as controls. Overall a composition of 10 mol% metal (in the case of Pd-Ni, 5 mol% of each metal) and 90 equivalent mol% SiO2 was maintained in the heat-treated films. Grazing incidence X-ray diffraction and transmission electron microscopy studies of the final heat-treated Pd-Ni doped films revealed the (111) oriented growth of the Pd-Ni alloy NPs, with an average size of 5.3 nm, residing inside the mesopores of the SiO2 film. We performed the C-C coupling reaction employing the film-catalysts and the progress of the reaction was monitored using a fluorimeter. Overall, only the Pd-Ni alloy NP doped film showed good catalytic activity with excellent recyclability. It has been determined that the higher oxidising ability of metallic Ni restricted the oxidation of Pd in the Pd-Ni alloy catalyst under the reaction conditions, leading to the maintained reusability in consecutive cycles.