Amplified visible light photocatalytic activity of mesoporous TiO2/ZnPc hybrid by cascade Mie light scattering

• We synthesized the mesoporous TiO2/phthalocyanice (ZnPc) hybrids in various sizes.
• We examine the visible light photocatalytic activity of the TiO2/ZnPc hybrids.
• We investigate the effect of Mie scattering on the photocatalytic activity.
• Scattering efficiency of the incident light is dependent on the diameter of hybrid.
• The hybrid with a size of 548 nm exhibits the highest photocatalytic activity.

We synthesize the anatase TiO2/zinc phthalocyanine (ZnPc) hybrids in various sizes (245–1188 nm) and examine the visible light photocatalytic activity of TiO2/ZnPc hybrids, in conjunction with their Mie light scattering ability. Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy show that ZnPc molecules are well-incorporated and dispersed on the surface of the TiO2, instead of being aggregates. From the field-emission scanning electron microscopy, dynamic light scattering, and nitrogen adsorption–desorption analysis, we confirm the formation of spherical TiO2/ZnPc hybrids in various sizes (245, 548, 798, 1188 nm in diameter), the large specific surface areas (up to 223.76 m2/g), and the mesoporous structures. The mesoporous TiO2/ZnPc hybrids show excellent photocatalytic efficiency (up to 89.93% after 90 min) toward the degradation of methylene blue under visible light irradiation, which is about 2 times of that of simple nanoparticular P25/ZnPc. Among the mesoporous TiO2/ZnPc hybrids, the hybrid with a size of 548 nm (P123–TiO2/ZnPc) exhibits the highest photocatalytic activity. The highest activity observed on P123–TiO2/ZnPc may be attributed to its efficient cascade Mie scattering effect under visible light irradiation.

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