Dual-strategy modification on g-C3N4 for highly efficient inactivation of Microcystis aeruginosa under visible light

g-C₃N₄ has great potential in photocatalytic inactivation of algal cells but still faces challenge due to the high recombination rate of electron-hole pairs, negative surface charge and low oxidation ability of photo-generated holes. Herein, the high temperature oxidation and protonation were used to synergistically improve the photocatalytic performance of g-C₃N₄ on Microcystis aeruginosa inactivation. Under visible light, inactivation percent of Microcystis aeruginosa by the best sample 15NCN reached 92.6%, much higher than that of g-C₃N₄ (6.8%). Results showed that high temperature oxidation induced to higher separation efficiency of photo-generated electron-hole pairs and higher oxidizing capacity of the generated holes. While the protonation endowed the g-C₃N₄ with positive surface charge which was beneficial for their adsorption on the negative charged algae cells. Therefore, it is helpful to increase the charge transfer between g-C₃N₄ and algae cells because of their inter-attraction. All the above factors induced to the high activity on the inactivation of Microcystis aeruginosa. This work provides a new design idea for the efficient inactivation of algal cells by carbon nitride-based photocatalysts.