Electrochemical Generation of Thin Silica Films with Hierarchical Porosity

Thin films with combined macropores (similar to 100 nm) and mesopores (similar to 3 nm) can be prepared by the electro-assisted deposition of a mesoporous silica material inside a polystyrene bead assembly. The filling of voids between the polystyrene beads template strongly depends on the deposition time, as demonstrated by systematic SEM analysis. Low deposition time leads only to very thin silica layers on the PS beads. Longer deposition time leads to the complete filling of the macroporous texture and to the growth of an additional overlayer with very well oriented pores normal to the electrode surface, The presence of mesopores into the film has been evidenced with using TEM, grazing incidence X-ray diffraction (GIXD), and Krypton sorption isotherm. The electrochemical characterization demonstrates that the hierarchical material is highly permeable to external reagents, being thereby promising for various applications involving such mass transport processes.