ZnO/Ag–Ag2O microstructures for high-performance photocatalytic degradation of organic pollutants

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Organic pollutants cause serious impacts on environment. A novel method to synthesize ZnO/Ag–Ag2O microstructures was developed for organic pollutant photocatalytic degradation. The 3D pompon-like Zn(OH)1.68(SO4)0.16·0.58H2O microspheres were firstly synthesized in a creative way by combining reaction in ethanol/water mixing layer and room-temperature self-assembly together. The length of nanosheets on Zn(OH)1.68(SO4)0.16·0.58H2O microspheres was controlled from ~ 0.8 to ~ 4.4 μm successfully. The method reduced both the processing temperature and reaction time compared with conventional ripening, which shortened catalysts’ production cycle, reduced production cost and simplified production condition. It holds great potential for industrial application. As traditional nanocatalysts are not easy to recycle and the residual nanocatalysts are also potential danger to the environment, our microsized ZnO/Ag–Ag2O photocatalysts inherit advantages of both nanoparticles and microspheres with enhanced removal efficiency and excellent recycle ability. Ag–Ag2O nanoparticles in ZnO/Ag–Ag2O microstructures were used to enhance the photocatalytic performance. 83.2% and 96.3% degradation efficiencies of Congo red were achieved by pure ZnO and ZnO/Ag–Ag2O microstructures after 80 min irradiation by UV light. 78.2% and 95.6% degradation efficiencies of methylene blue were achieved by pure ZnO and ZnO/Ag–Ag2O after 40 min under UV radiation. The degradation rate constants by ZnO/Ag–Ag2O microstructures are 0.04056 min−1 for Congo red and 0.07629 min−1 for methylene blue respectively. The ZnO/Ag–Ag2O photocatalyst showed excellent stability and reusability, since it was reused at least 5 times without any extra treatment. The ZnO/Ag–Ag2O microstructures may hold potential for organic pollutant treatments.