Photoactivity of decahedral TiO2 loaded with bimetallic nanoparticles: Degradation pathway of phenol-1-13C and hydroxyl radical formation

Abstract

Decahedral TiO2 decorated with bimetallic nanoparticles were synthesized via radiolysis and photodeposition method. The effect of bimetallic surface composition (Ag_Pt, Ag_Au, Au_Pd, Au_Pt) as well as deposition technique (simultaneous or sequential) on the photocatalytic activity in phenol degradation and efficiency of hydroxyl radicals generation under UV–vis light irradiation were investigated. Modified and pristine decahedral TiO2 anatase with exposed {001} were characterized by X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), transmission electron microscopy (TEM) with energy-dispersive X-ray (EDX) spectroscopy, scanning electron microscopy (SEM), inductively coupled plasma-mass spectrometry (ICP-MS) and X-ray photoelectron spectroscopy (XPS). The gas chromatography-mass spectrometry was employed to detect organic intermediates to establish degradation pathway of isotopically labeled (1-13C) phenol. The modification with Pt and Ag nanoparticles induced an increase in photocatalytic activity of phenol degradation under UV–vis light irradiation (79% of phenol was degraded after 90min of irradiation). The main by-products detected in phenol oxidation were catechol, hydroquinone, malonic, fumaric and maleic acid. The results indicated the formation of isotopically labeled and unlabeled maleic acid. It was noticed that all samples sequentially photodeposited on TiO2 surface exhibited higher OH radicals generation compared to pristine TiO2. Our results suggest that synergistic effects between specifically engineered TiO2 nanocrystals and unique properties of loaded bimetallic nanoparticles can enhance the charge separation of photoinduced carriers.