Ag2C2O4 and Ag2C2O4/TiO2 nanocomposites as highly efficient and stable photocatalyst under visible light: Preparation, characterization and photocatalytic mechanism

Abstract

Ag2C2O4 and Ag2C2O4/TiO2 (Commercial P25-TiO2) nocomposites with different weight ratios of Ag2C2O4 to P25-TiO2 (denoted as Ag2C2O4/TiO2-0.02, Ag2C2O4/TiO2-0.08, Ag2C2O4/TiO2-0.15, Ag2C2O4/TiO2-0.25, Ag2C2O4/TiO2-0.3) were synthesized by a facile liquid precipitation method. The photocatalytic activity of samples was evaluated by the degradation of propylene and acetaldehyde gas under visible light irradiation. All the samples displayed a highly efficient and stable photocatalytic activity. Furthermore, compared to pure Ag2C2O4 and P25-TiO2 (used as reference), Ag2C2O4/TiO2 nanocomposites showed much higher photocatalytic activity and Ag2C2O4/TiO2-0.25 possessed the highest photocatalytic activity. The kinetic behavior of Ag2C2O4/TiO2-0.25 was well accordant with a pseudo-first-order reaction and the reaction rate constants were calculated to be 11.13h−1 and 0.5376h−1 for the degradation of propylene and acetaldehyde, respectively. The mechanism of highly efficient and stable photocatalytic activity was discussed. On the one hand, Ag2C2O4 undergoes firstly photo-corrosion during the initial photocatalytic process generating nascent metallic Ag on the surface of Ag2C2O4, which subsequently endowing the Ag@Ag2C2O4 with visible light phtocatalytic activity due to the plasma resonance of Ag. On the other hand, Ag2C2O4/TiO2 nanocomposites also experience the same journey resulting in the formation of Ag@Ag2C2O4/TiO2. Differently from Ag@Ag2C2O4, two paths are involved to separate the electron and hole excited by the photon of nascent metallic Ag so as to acquire much higher phtocatalytic activity for Ag@Ag2C2O4/TiO2.