One-pot preparation of hierarchical CuO hollow spheres for improved visible-light photocatalytic properties.

As visible light photocatalysts, narrow bandgap semiconductors can effectively convert solar energy to chemical energy, exhibiting potential applications in alleviating energy shortage and environmental pollution. CuO hollow spheres with a narrow band gap and uniform hierarchical structures have been fabricated in a controlled way. The one-pot solvothermal method without any template is simple and facile. The morphologies, crystal structures, composition, specific surface areas, and optical and photoelectric properties of the products were analyzed by various techniques. The hollow and solid CuO spheres could be fabricated by controlling the reaction time, and a possible growth process of the CuO hollow spheres was revealed. The degradation of methyl orange (MO) was used to investigate the visible-light catalytic properties of the CuO samples. More than 90% of MO is degraded under visible light illumination of 20 min, exhibiting a quick catalytic reaction. The rate constant of the CuO hollow spheres was 2.54 times and 46.6 times larger than those of the CuO solid spheres and commercial CuO powder, respectively. The possible photocatalytic mechanism of MO was revealed over CuO hollow spheres through the detection of active species. The as-prepared CuO hollow spheres display improved visible-light catalytic activity and stability, indicating their potential application in wastewater treatment.