Bioinspired ZnO-based solar photocatalysts for the efficient decontamination of persistent organic pollutants and hexavalent chromium in wastewater

Abstract

Biomimetic/bioinspired engineering and sulfidation processes are effective strategies for improving the visible light-driven photocatalytic performance of ZnO photocatalysts. A facile electrodeposition process in high oxygen-flux conditions was used to synthesize well-defined fractal micro/nanoferns, consequently increasing the photocatalyst’s light-trapping capability and the accessible active surface. Next, a simple sulfidation process was used to form a thin layer of ZnS, producing ZnO@ZnS core@shell micro/nanoferns, thereby tuning the optoelectronic properties and extending the photoresponse to the visible region. The ZnO@ZnS micro/nanoferns exhibited clear superiority over other ZnO photocatalysts in the photooxidation of persistent organic pollutants (POPs) and the photoreduction of Cr(VI). Their excellent photocatalytic performance allowed the photodegradation under UV-filtered sunlight of nearly 97% of methylene blue after 60 min; the mineralization of >98% of a mixture of methylene blue, 4-nitrophenol, and rhodamine-B after 210 min; and the removal of nearly 65% of Cr(VI) after 180 min. In addition, the ZnO@ZnS micro/nanoferns demonstrated a good ability to decontaminate an inorganic-organic bipollutant system, with promising potential to leverage synergistic effects. Finally, these micro/nanoferns presented great recyclability and reusability for both photooxidation and photoremediation processes. These findings support that sulfidation and biomimetic engineering can be a superior route for designing efficient sunlight-driven ZnO-photocatalysts for water decontamination.