Synthesis of Cu2O nanocrystals/TiO2 photonic crystal composite for efficient p-nitrophenol removal

Cu2O nanocrystals/TiO2 photonic crystal (Cu2O NCs/TiO2 PC) photocatalyst was prosperously synthesized and applied to the degradation of p-nitrophenol (PNP). The composite were characterized with scanning electron microscopy (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma atomic emission spectrometer (ICP-AES), and UV-vis diffuse reflectance spectrum (UV-vis DRS) techniques. The PNP photocatalysis was performed by varying Cu2O NCs loading amount, PNP initial concentration, and solution pH value. Under optimal experiment conditions, the kinetic constant of 0.85-Cu2O NCs/TiO2 260 (where 0.85 represents the mass fraction of Cu2O in composite, and 260 denotes the PC structure derived from 260 nm polystyrene spheres) was 4.57-fold higher than that using pristine TiO2. The improvement was thanks to the enhanced light harvest by integrating Cu2O NCs with TiO2 PC in which the light absorption were efficiently strengthened and the increased quantum yield owing to the p-n junction between TiO2 and Cu2O. The superoxide anions originated from the one electron reduction of oxygen molecules by the conduction band electrons was responsible for PNP removal. According to the identified intermediates, aliphatic alcohols, aldehydes and carboxylic acid, the possible PNP decomposition path was put forward. We believe this research could supply valuable knowledge for PNP decomposition and impel the technical development of photocatalysis.