Photocatalytic nitrate reduction over Pt–Cu/TiO2 catalysts with benzene as hole scavenger

Nitrate and benzene are commonly identified contaminants in groundwater. In this study, a series of TiO2 supported Pt–Cu bimetallic catalysts were prepared and photocatalytic nitrate reduction in the presence of benzene was investigated. The catalysts were characterized by XRD, N2 adsorption, TEM, X-ray photoelectron spectroscopy and IR spectroscopy of CO adsorption. The results showed that Pt–Cu alloy was formed in TiO2 supported bimetallic catalysts except for the bimetallic catalyst with TiO2 calcined at 700 °C as the support. In addition, higher alloy dispersion and smaller metal particle sizes could be obtained on TiO2 calcined at 300 °C compared to those calcined at 500 and 700 °C. For photocatalytic nitrate reduction in the presence of benzene, nitrate was mainly converted to ammonia or nitrite over Pt/TiO2 or Cu/TiO2, respectively, whereas TiO2 supported Pt–Cu bimetallic catalysts exhibited a considerable N2 selectivity for photocatalytic nitrate reduction. The catalytic activity and N2 selectivity of the supported bimetallic catalyst was strongly dependent on TiO2 calcination temperature, Pt/Cu ratio and metal loading amount. The bimetallic catalyst with TiO2 calcined at 300 °C as the support, Pt loading amount of 5 wt.% and Pt/Cu ratio of 4/1 displayed higher N2 selectivity compared with other bimetallic catalysts. The present results demonstrate the selective nitrate reduction over Pt–Cu/TiO2 catalysts with benzene as the hole scavenger, highlighting the validity of simultaneous removal of aqueous nitrate and benzene by photocatalysis.