Visible-light-driven photocatalytic and photoelectrocatalytic debromination of BDE-47 on a macroporous silicon/graphene heterostructure

Macroporous silicon/graphene (MPSi/Gr) heterostructure was fabricated by electrophoresis depositing Gr sheets on the surface of MPSi and then annealing the samples to improve adhesion and electrochemical property. In the photoelectrochemical measurements, MPSi/Gr heterostructure displayed stable and high photocurrent compared with MPSi. The stability profits from protection of Gr layer, and the enhancement of photocurrent is ascribed to effective photogenerated charge separation of MPSi/Gr heterostructure. The results of photocatalytic and photoelectrocatalytic debromination of BDE-47 showed MPSi/Gr possesses excellent photocatalytic capability, and this capability can be enhanced by applying a bias potential. The kinetic constant of MPSi/Gr (1.13 h−1) heterostructure in photoelectrocatalytic process was five times as much as that of MPSi/carbon film heterostructure (0.22 h−1), indicating Gr, as a charge collector which can promote separation and transfer of photogenerated carries, is superior to other carbon materials for building heterostructures. The majority (87.1%) of debromination was induced by visible light which was confirmed by comparing reaction efficiency under xenon lamp irradiation to that under the same lamp irradiation via a 422 nm filter. According to the results of photocatalytic debromination experiments with O2 or N2 bubbling, debromination mechanism of BDE-47 was proposed as a reductive debromination by photogenerated electrons.

► Macroporous Si/graphene photocatalyst is employed in pollution control for the first time. ► The heterostructure works stably in aqueous solution. ► The heterostructure displays high photocatalytic dehalogenation capability.