Enhanced photocatalytic activity of biosynthesized Au-Ag/TiO2 catalyst by removing excess anchored biomolecules

A green bioreduction method was used to prepare highly efficient supported TiO2 photocatalysts with bimetallic (Au-Ag) nanoparticles at room temperature using Cinnamomum camphora leaf extract as both the protective agent and reducing agent. The resulted Au-Ag/TiO2 exhibits high photocatalytic activity toward the degradation of organic dyes. It was demonstrated that after some of the biomolecules were removed through ionic-liquid extraction and/or calcinations, the Au-Ag/TiO2 photocatalyst exhibits significantly enhanced catalytic performance toward the degradation of methyl orange compared to the pristine untreated catalyst. As a result, 300 mL of 20 mg/mL methyl orange can be fully degraded in 30 min. These can be explained by the sufficient biomolecules could protect the nanoparticles stay in small size, but excess biomolecules played an unfavorable role in hindering the electron transportation during the catalytic reaction. The low-cost preparation, the high activity, together with the good stability and recyclability make this developed Au-Ag/TiO2 a promising photocatalyst toward the degradation of wastewater.