Understanding silica-supported metal catalysts: Pd/silica as a case study

Supported metal catalysts, particularly noble metals supported on SiO ₂, have attracted considerable attention due to the importance of the silica-metal interface in heterogeneous catalysis and in electronic device fabrication. Several important issues, e.g., the stability of the metal-oxide interface at working temperatures and pressures, are not well-understood. In this review, the present status of our understanding of the metal-silica interface is reviewed. Recent results of model studies in our laboratories on Pd/SiO ₂/Mo(112) using LEED, AES and STM are reported. In this work, epitaxial, ultrathin, well-ordered SiO ₂ films were grown on a Mo(112) substrate to circumvent complications that frequently arise from the silica-silicon interface present in silica thin films grown on silicon.