Metal modification on TiO2 nanoparticles for enhanced photocatalytic conversion of lignin

Biomass has been attracting increasing attention as an alternative resource to reduce fossil fuel consumption. Thailand is a significant producer of biomass resources such as sugarcane, bagasse, and rice husk. The main component of biomass is cellulose, hemicellulose, and lignin. Lignin was left as waste from many processes, including paper or pulp process, biomass ethanol production, and wood extractions. Various processes were developed to upgrade lignin into high-value chemicals, for example, depolymerization, hydrothermal, alkali pyrolysis, and electrochemical. However, these processes have high temperature and energy consumption. Photocatalysis is considered as a favorable technology for various applications due to its environmentally friendly method and low cost, and low energy consumption. TiO2 photocatalyst has received the most research attention because of its high chemical stability, nontoxicity, high photoactivity, and low cost. In this work, the modification of TiO2 with Ag loading to enhance lignin conversion was studied. TiO2 photocatalysts were synthesized by sol-microwave method, while Ag loading TiO2 was prepared with 1% Ag by using wetness impregnation technique. AgNO3 was used as a precursor and slowly dropped into TiO2 powder. Then, Ag-TiO2 photocatalysts were calcined at 400 C for 3 h under air conditions. Morphology and physical properties of Ag-TiO2 were investigated by various methods such as field-emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), and x-ray diffraction (XRD). Ag-TiO2 photocatalysts could enhance photocatalytic lignin conversion by 33%. It can conclude that Ag plays an essential role in enhancing the photocatalytic activity of TiO2 activity due to improved charge separation and electron-hole recombination reduction by acting as an electron acceptor.