Bioinspired ZnO-Based Solar Photocatalysts for the Efficient Decontamination of Persistent Organic Pollutants and Hexavalent Chromium in Wastewater

Albert Serrà,Elvira Gómez,Laetitia Philippe

doi:10.3390/catal9120974

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.

Highlights

ZnO photocatalysts are widely regarded as some of the most attractive semiconductor materials for photocatalytic engineering because of their low cost, high photosensitivity, sustainability properties, high redox potential, and high photocatalytic activity
Electrodeposition has proven to be an excellent technique for the deposition of vertically-aligned
The single most important aspect is the reduction of an oxygen precursor at the interface electrode, resulting in the electro-generation of hydroxyl ions and, the electro-precipitation of

Summary

Introduction

ZnO photocatalysts are widely regarded as some of the most attractive semiconductor materials for photocatalytic engineering because of their low cost, high photosensitivity, sustainability properties, high redox potential, and high photocatalytic activity. The development of hierarchical architectures promises to improve the adsorption of pollutants and the light-trapping capability of photocatalysts, as well as significantly enhancing their performance. Another approach for developing efficient photocatalysts is the integration of biomimetic and bioinspired thinking, such as in the design of novel sunlight-driven materials, devices, and structures. These take inspiration from the idea that sunlight has been the principal engine of most biological processes for millions of years. New and efficient photocatalysts developed through these methods show great promise, especially for water decontamination [1,7,8,9,10]

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Conclusion