Ti-containing hybrid mesoporous organosilicas as photocatalysts for H2 production from ethanol

Abstract

A series of complex organic-inorganic mesoporous materials were successfully synthesized by a microwave-assisted method that allowed the preparation of periodic mesoporous organosilicas (PMOs) with Ti (IV) forming part of the structure (Ti-PMOs). Materials were characterized using N2 adsorptionedesorption isotherms, powder X-ray diffraction (XRD), transmission and high resolution transmission electron microscopy (TEM and HRTEM), Raman, infrared, UVevisible diffuse reflectance (UVevis RDS), X-ray photoelectron (XPS), photoluminescence (PL) and electrochemical impedance (EIS) spectroscopy, and transient photocurrent measurements. Samples labeled Ti10-PMO, Ti20-PMO and Ti40- PMO (with Si/Ti molar ratio of about 10, 20 and 40), showed crystal-like characteristics and high specific surface area (742e829 m2 g-1). Ti-PMOs were studied in the photocatalytic H2 evolution from an aqueous ethanol solution under UVevisible irradiation. Ti-PMOs showed a better photocatalytic behavior than PMO and this is related with the presence of tetrahedral Ti(IV) in the PMOs network. Ti-PMOs displayed a lower barrier for the electron transfer and a more efficient charge separation than PMO. The highest H2 production was obtained with Ti20-PMO photocatalyst; after 4 h of irradiation, 2042 mmol H2 gcat 1 were obtained, which was about 20 times higher than that obtained with a reference commercial TiO2 (P25).