A novel porous Al2O3 layer/AgNPs–Hemin composite for degradation of azo dyes under visible and UV irradiation

• A method of synthesizing PAOG/AgNPs–Hemin composite for photocatalysis.
• PAOG has a large BET surface area.
• This novel composite showed enhanced broad spectrum photocatalytic activity.
• Cycled tests of PAOG/AgNPs–Hemin composite showed virtually no reduction in photocatalysis capacity.

In this paper, a photocatalytic system for effectively degrading azo dyes is described. The nanostructured porous Al2O3 layer on glass substrate (PAOG)/silver nanoparticles (AgNPs)–Hemin composites were synthesized via photochemical reduction of Ag, self-assembly of 11-mercaptoundecanoic acid (MUA) on AgNPs and subsequently linking Hemin to MUA via coordination bond. PAOG as a nanoporous template was chemically durable, highly porous and allowed chemicals conveniently immobilized on the glass surface. PAOG had a BET surface area of 151 m2/g which facilitated the immobilization of AgNPs. The composite was characterized by BET surface area measurements, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray analysis (EDX), Fourier transform infrared (FTIR) spectrometer and X-ray photoelectron spectroscopy (XPS). The photoreaction degradation processes were examined by UV/vis spectroscopy. Methyl orange (MO) and Acid red 18 solutions were used to evaluate the photocatalytic performance of PAOG/AgNPs–Hemin composite under visible light and UV irradiation. Compared with PAOG/Hemin, the PAOG/AgNPs–Hemin composite had enhanced photocatalytic efficiency due to higher electron transfer efficiency from AgNPs to Hemin. This novel composite with enhanced broad spectrum photocatalytic properties has promising potentials in degradation of dyes by UV and visible light utilization.

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