Enhanced photocatalytic performance and a mechanistic study of novel black phosphorus/graphene/TiO₂ composite membrane for o-chlorophenol removal

The heterogeneous catalysis of the composite membrane not only exerts the synergistic effect of different materials but also enable the recyclable use of catalysts, making it an ideal and sustainable strategy for removing pollutants in water. In this study, a novel black phosphorus/graphene/titanium dioxide (BP/GR/TiO₂) membrane was successfully prepared through the sol-gel method. The composite membrane not only overcame the instability of black phosphorus and the rapid recombination of e^-/h⁺ pairs in titanium dioxide but also synergized with GR to produce a new reactive oxygen species (ROS), singlet oxygen (¹O₂), with a longer lifetime and migration distance. This ROS was a highly selective reactive species responsible for the efficient degradation and, consequently, the removal of o-chlorophenol (o-CP). Specifically, BP simultaneously enhanced the specific surface area and visible light absorption of BP/GR/TiO₂, resulting an o-CP degradation efficiency of up to 98.1% after 5 h of simulated solar irradiation with 0.3% BP doping. The photocatalytic mineralization efficiency of o-CP after 10 h of light was 60.1%, which was 1.41 times higher than that of the corresponding BP/TiO₂ membrane. Following recycling, the degradation efficiency and rate of BP/GR/TiO₂ were 1.71 and 1.79 times higher than those of BP/TiO₂, respectively, demonstrating excellent stability and recyclability.