Enhanced disinfection application of Ag-modified g-C3N4 composite under visible light

Ag/g-C3N4 composite photocatalyst, which was synthesized by thermal polymerization of melamine precursor combined with the photo-assisted reduction method, was applied as an efficient visible-light-driven photocatalyst for inactivating Escherichia coli (E. coli). The composite photocatalysts exhibited significantly enhanced photocatalytic disinfection efficiency than pure g-C3N4 powders. The mechanism of enhanced disinfection activity was systematically investigated by UV–visible diffuse reflectance spectra, photoluminescence spectra, and photo-electrochemical methods including photogenerated current densities, electrochemical impedance spectroscopy (EIS) spectra and Mott–Schottky plots. The enhanced photocatalytic bactericidal effect was attributed to the hybrid effect from Ag and g-C3N4, which resulted in enhanced adsorption of visible light, reduced recombination of free charges, rapid separation and transportation of photogenerated electrons–holes. The disinfection mechanism was studied by employing chemical scavengers and ESR technology, indicating the important role of h+ and e−. Considering the bulk availability and excellent disinfection activity of Ag/g-C3N4, it is a promising solar-driven photocatalyst for cleaning microbial contaminated water in practice.