Two-dimensional g-C₃N₄/TiO₂ nanocomposites as vertical Z-scheme heterojunction for improved photocatalytic water disinfection

Developing highly active photocatalysts towards effective microorganism inactivation is a green and energy-smart strategy in response to the growing demands to water quality under the background of the water crisis. Here, a vertical face-to-face heterojunction is fabricated by horizontally assembling TiO₂ nanosheets with {001} facets exposed on graphitic carbon nitride (g-C₃N₄) sheets through a facile hydrothermal driving coupling. The vertical heterojunction could almost completely disinfect 10³ CFU/mL E. coli within 30 min under solar light, which is more efficient than the physically mixed composite and pure g-C₃N₄ and TiO₂. The two-dimensional (2D) morphology provides ample surface area in forming the vertical heterojunction and enables intimate contact which is advantageous to charge transfer between g-C₃N₄ and TiO₂. A Z-scheme charge transportation mechanism is confirmed through band structure analysis and reactive species (RSs) probing and trapping experiments. In comparison with physically mixed composite and the single-phase counterparts, the nanocomposite based on a Z-scheme electron transfer mode effectively prompts charge pair dissociation and subsequently encourages bacterial inactivation by boosting the generation of RSs. The constructing vertical Z-scheme heterojunction highlights the potential of 2D nanomaterials for accelerated water sterilization.