Formation of stable microporous core-shell V2O5/SiO2 colloidal particles potential for heterogeneous catalysis

Abstract

An approach for the synthesis of stable core-shell V2O5/SiO2 colloidal particles has been proposed. First, ammonium vanadate particles ∼ 300 nm in size, which act as a precursor for vanadium pentoxide synthesis, are obtained from NH4VO3 saturated solution. To prevent possible changes in morphology of the obtained particles during the synthesis of V2O5 they are coated with silica shell via hydrolysis of tetraethoxysilane. The formed SiO2 shell possesses microporous structure with an average size of pores ∼ 1.5 nm and specific surface area 170 m2/g. It is shown that the presence of pores makes it possible to provide efficient removal of decomposition products during conversion of NH4VO3 to V2O5 during annealing at 550 °C and preserve the shape and size of the core-shell particles. The obtained V2O5/SiO2 particles are of ∼ 700 nm in size have an almond-like shape and form a stable aqueous suspension. It is found that they exhibit intense broadband room-temperature photoluminescence with maximum intensity at 660 nm. The shell retains its porous structure after annealing and gives access to the core of particles – V2O5, which allows complete conversion of V2O5 to, for example, V2O3 and makes the core-shell particles promising for use in heterogeneous catalysis.