Trash to treasure: Green synthesis of novel Ag2O/Ag2CO3 Z-scheme heterojunctions with highly efficient photocatalytic activities derived from waste mussel shells

Shells, valuable renewable natural resources with particular mechanical properties and structures, are mostly abandoned as waste and accumulated in environment, leading to serious pollution and resource waste. To realize the high value reutilization and environmental protection, here, novel Ag-based photocatalysts were in-situ fabricated via a facile ball milling method using waste mussel shells as precursors for the first time. The composition, structure and photocatalytic activity of the obtained Ag-based photocatalysts can be regulated by the alkalinity of the reaction system caused by different treatments towards mussel shells. Among the obtained products, the Ag2O/Ag2CO3 Z-scheme heterojunctions with massive oxygen vacancies displayed the strongest visible-light photocatalytic ability and superior reusability in degrading sulfadiazine, which can be attributed to the wider light response region and faster separation of photoinduced charge carriers. Besides, the photocatalytic mechanism was speculated according to the tests of radicals trapping, electron spin resonance and simulation calculations, verifying the charge transfer direction and chief roles of ·O2− and h+ during the photocatalytic reaction. Above all, this study not only provides a convenient in-situ solid-state strategy to construct novel Ag-based photocatalysts with excellent photocatalytic activity, but also opens up a new perspective towards high value reutilization of waste shells in environmental remediation, “One Stone Two Birds” realizing the “control of waste by waste” and “trash to treasure”.