Rapid photocatalytic debromination on TiO2 with in-situ formed copper co-catalyst: Enhanced adsorption and visible light activity

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The cheap metal Cu particles in-situ loaded on TiO2 surface is able to co-catalyze the photocatalytic debromination of polybrominated pollutants. Over 15 times of enhancement for the reductive debromination of deca-brominated diphenyl ether (BDE209) over Cu/TiO2 is achieved, relative to that on the bare TiO2. Moreover, the presence of metal copper markedly changes the distribution of the formed intermediates, indicating the change in the debromination mechanism because of the co-catalysis of metal Cu. The detailed ex-situ and in-situ characterizations of the Cu/TiO2 photocatalyst indicate that the copper remains its Cu0 valence state in photocatalytic turnover. The mechanistic investigation suggests that the presence of metal copper nanoparticles greatly enhance the adsorption of hydrophobic BDE209 on the photocatalyst, which facilitates the electron transfer from the conduction band of TiO2 to the pollutants. Our experimental results also implies that the interaction of BDE209 with metal copper co-catalyst would position-specifically activate the C-Br bonds during the dissociative electron transfer. We further show that the surface plasmon resonance of metal copper can contribute to the enhancement of photocatalytic activity by utilizing the visible-light part of the irradiation. The present study provides a simple and economic method for elimination of organobromide pollutants, and would be promising in reductive dehalogenation by other techniques.