Efficient photoactivity of TiO2-hybrid-porous nanocomposite: Effect of humidity

Abstract

TiO2 photocatalyst and Cu-BTC metal organic framework were successfully coupled via sol-gel method to form a hybrid porous nanocomposite (TiO2-hybrid-PNC). X-ray diffraction (XRD) results revealed the intense characteristic TiO2 anatase peaks. Surface area (BET) measurements showed type IV adsorption isotherm with the formation of a mesoporous structure for TiO2-hybrid-PNC. Scanning electron microscopy elemental analysis-mapping images (SEM-EDX) and X-ray photoelectron spectra (XPS) confirmed the existence of TiO2 nanoparticles in the hybrid porous structure. UV–Vis diffuse reflectance (UV–Vis DRS) absorption profile of TiO2-hybrid-PNC had impacts from both TiO2 and Cu-BTC. The lower photoluminescence (PL) intensity of TiO2-hybrid-PNC possessed an efficient charge separation and inhibited electron-hole recombination compared to the Cu-BTC. Dark absorption capacities and photoactivities of Cu-BTC and TiO2-hybrid-PNC were discussed in terms of electronic interactions using methyl orange (MO) as probe molecule. Effect of humidity on the dark abilities and photocatalytic performances of Cu-BTC and TiO2-hybrid-PNC was investigated after their exposure to 40%, 67% and 84% relative humidity (RH) values. According to XRD and SEM analysis, structural features of TiO2-hybrid-PNC were preserved under humid conditions. Photocatalytic efficiency of TiO2-hybrid-PNC enhanced with increments in RH percentages owing to the formation of more hydroxyl radicals. TiO2-hybrid-PNC (84% RH) revealed a higher rate constant than that of TiO2-hybrid-PNC based on pseudo-first order kinetics and Langmuir-Hinshelwood model. Durabilities of TiO2-hybrid-PNC and TiO2-hybrid-PNC (84% RH) were also confirmed after four cycling experiments.