Carbon quantum dots embedded with mesoporous hematite nanospheres as efficient visible light-active photocatalysts

Carbon quantum dots (CQDs) and mesoporous hematite (alpha-Fe2O3) complex photocatalysts were successfully prepared using a facile solvent-thermal process in an aqueous solution. Mesostructured alpha-Fe2O3 clusters with a high surface area and a porous framework were an important consideration in the design of the photocatalysts because such structures enhance the absorption of photons and promote the decomposition of organic pollutants. More significantly, the CQDs in this catalyst play a pivotal role in improving the photocatalytic activity under visible light irradiation. The nanocomposites were characterized using X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, energy-dispersive spectroscopy, field-emission scanning electron microscopy, transmission electron microscopy, dynamic light scattering methods, ultraviolet-visible spectroscopy, and other techniques. The results confirmed the formation of CQD/mesoporous alpha-Fe2O3 hybrid clusters with a uniform size (about 700 nm), three-dimensional spherical morphologies, a large internal surface area (up to 187 m(2) g(-1)), and a wormhole-like mesopore structure. Moreover, these novel composite catalysts displayed a continuous absorption band in the visible region. Photocatalytic studies of the CQD-embedded mesoporous alpha-Fe2O3 showed excellent photocatalytic efficiency (up to 97% capacity retention after three cycles) toward the degradation of organic compounds in aqueous media under visible light irradiation. The relationship between the physicochemical properties and the photocatalytic performance in our system is described and discussed on the basis of the results.