Efficient photocatalytic degradation of tetrabromodiphenyl ethers and simultaneous hydrogen production by TiO 2 -Cu 2 O composite films in N 2 atmosphere: Influencing factors, kinetics and mechanism.

TiO2 -Cu2 O photocatalyst composite film with a heterostructure was synthesized on a copper substrate for 2,2',4,4'-tetrabromodiphenyl ether (BDE47) reduction. First, Cu2 O film was synthesized by the electrochemical deposition method, and then TiO2 was coated on the surface of the Cu2 O film. The morphology, surface chemical composition and optical characteristics of TiO2 -Cu2 O film were characterized. The degradation efficiency of BDE47 and hydrogen production by TiO2 -Cu2 O films was higher than those by pure TiO2 or Cu2 O films. The highest BDE47 degradation efficiency of 90% and hydrogen production of 12.7mmolLliq -1 after 150min were achieved by 67%TiO2 -Cu2 O films. The influencing factors were investigated in terms of film component, solvent condition, and initial pH. A kinetics study demonstrated that BDE47 degradation followed a pseudo-first-order model. Photocatalytic apparent reaction rate constant of BDE47 by TiO2 -Cu2 O films was 0.0070min-1 , which was 3.3 times of that by directly photolysis process. During photocatalytic debrmination process, the photogenerated holes were reserved in the valance band of Cu2 O to oxidize methanol. Meanwhile, the partial photogenerated electrons transferred to the conduction band of TiO2 and directly eliminated the ortho-Br of BDE47 and yielded BDE28 and BDE15. The other partial photogenerated electrons reduced protons (H+ ) to form atomic hydrogen (H°), which could substitute the para-Br of BDE47 and generated BDE17 and produce hydrogen.