Construction of heterojunction of BiOBr nanosheets grown in situ on octahedral UiO-66 with improved photocatalytic activity
摘要
A novel 3D octahedral BiOBr/UiO-66 heterostructure photocatalyst was synthesized through the in-situ growth of BiOBr nanosheets on octahedral UiO-66 at ambient temperature. This heterojunction of type II exhibits a substantial specific surface area, promoting intimate interfacial contact which favors carrier transmission and enhances the contact area of the semiconductor surface reaction. The morphology and structure of the catalyst were characterized via SEM and TEM. Transient photocurrent and electrochemical impedance spectroscopy confirm the advantageous nature of the heterojunction for carrier separation. Further investigation delves into the photocatalytic degradation of RhB. After 70 min of light irradiation, the removal rate of RhB reached a remarkable 94.9% using the 60% BiOBr/UiO-66 composition. Furthermore, the apparent kinetic constant of the 60% BiOBr/UiO-66 was measured to be 0.03522 min−1, surpassing pure BiOBr (0.01238 min−1) by a factor of 2.9 and UiO-66 (0.00035 min-1) by a factor of 100. Experiments involving free radical capture provide evidence that superoxide radicals (·O2−), electrons(e−) and holes (h+) are the principal active species during the photodegradation process. Accordingly, a proposed photocatalytic mechanism for the BiOBr/UiO-66 heterojunction emerges.