Understanding the potential band position and e-/h+ separation lifetime for Z-scheme and type-II heterojunction mechanisms for effective micropollutant mineralization: Comparative experimental and DFT studies

•Oxidized GCN and reduced TiO2 composites are synthesized by MWH method.•Light sources (sunlight and LED) determine the electrons transfer mechanism.•Negatively charged pollutants cannot be fully degraded by ·O2− due to repulsion.•Potential valence band position is important for ROS generation.•In-built electric field on the interface allows electrons to migrate via Z-scheme.