Acid-induced molecule self-assembly synthesis of Z-scheme WO3/g-C3N4 heterojunctions for robust photocatalysis against phenolic pollutants

Searching for effective strategies of boosting charge carrier separation and improving photooxidation ability are highly desirable to design graphitic carbon nitride-based photocatalysts for efficient organic pollutant degradation. Here we demonstrate an in situ acid-induced self-assembly of melamine and sodium tungstate method combined with hydrothermal treatment, by forming WO3/melamine-cyanuric acid supramolecular complex, to fabricate porous sheet-like WO3/g-C3N4 heterojunctions with oxygen doping; meanwhile, the morphology of WO3/g-C3N4 nanosheets can be further regulated by selecting different short-chain carboxylic acids. The heterojunctions exhibit enhanced visible-light photocatalytic activity than bulk g-C3N4 and supramolecule-based g-C3N4 in degradation of phenolic pollutants, acetaminophen and methylparaben. The tests including active species trapping, photoelectrochemistry and photoluminescence firmly evidence that the extraordinary Z-scheme charge transfer manner plays dominated role to this excellent activity, which can accelerate charge carrier separation and retain powerful redox ability of electrons on conduction band of g-C3N4 and holes on valence band of WO3 simultaneously; additionally, porous sheet-like nanostructures and oxygen doping also positively influence the activity via improving light harvesting, providing plentiful active sites, shortening charge carrier migration distance and further facilitating charge carrier separation. LC-MS analysis and TOC monitoring find the target pollutants are completely degraded under oxidation of holes, superoxide and hydroxyl radicals.

Automated summary

The method of in situ acid-induced self-assembly of melamine and sodium tungstate combined with hydrothermal treatment was used to fabricate oxygen-doped porous sheet-like WO3/g-C3N4 heterojunctions, which exhibit enhanced visible-light photocatalytic activity for the degradation of phenolic pollutants, acetaminophen, and methylparaben. The extraordinary Z-scheme charge transfer manner plays a dominant role in accelerating charge carrier separation and retaining powerful redox ability, while the porous sheet-like nanostructures and oxygen doping positively influence the activity by improving light harvesting, providing plentiful active sites, shortening charge carrier migration distance, and facilitating charge carrier separation.