Effects of different exposed-facets on photocatalytic activity of BiOBr /Bi2Ti2O7 heterostructure and mechanism analysis

In this paper, the novel heterojunctions of Bi2Ti2O7 and BiOBr with different crystal facets ({001} and {010}) were synthesized by in-situ precipitation method under room temperature. The structure and properties of the materials were analyzed. The photodecomposition properties of the materials were studied by using rhodamine B (RhB) and ciprofloxacin (CIP) as targets. The possible mechanism of the difference of facet-engineering on photocatalytic degradation was studied. The XPS results indicated that the high-quality interfacial connection existed in Bi2Ti2O7/BiOBr heterostructure. It was found that the RhB and CIP degradation rates of Bi2Ti2O7/BiOBr–{010} photocatalyst are 2.05 and 1.82 times higher respectively than that of Bi2Ti2O7/BiOBr–{001} under visible light. This enhancement was mainly attributed that laminate BiOBr dominating {010} exposed-facet with higher the specific area (SBET) combined with spherical Bi2Ti2O7, which extended SBET and provided more active site; furthermore, the formation of the type-II band location and strong interfacial interaction vastly weaken the barrier of electron transfer, promoting the quantum efficiency. The synergistic effect of facet-engineering and composite structure were discussed in detail, providing significant reference to design highly active photocatalyst.