Photocatalytic dyes degradation on suspended and cement paste immobilized TiO2/g-C3N4 under simulated solar light

To overcome the shortcomings of fast recombination of photo-induced carriers and powder recycling difficulty of graphitic carbon nitride (g-C3N4), a powder suspension system containing TiO2/g-C3N4 and a cement paste immobilization of TiO2/g-C3N4 were fabricated through pyrolysis of urea and P25 TiO2, and spraying method, respectively. The phase composition, microstructure, element chemical state, optical properties, and photocatalytic degradation of dyes were investigated. TiO2 particles were attached closely to the surfaces of g-C3N4. TiO2/g-C3N4 had broader light absorption ranges and a lower recombination rate of photo-induced carriers. During the photocatalysis, h+, •O2- and •OH were the main active species. The heterojunction structure of TiO2/g-C3N4 belonged to a Z-scheme heterojunction. The TiO2/g-C3N4 powders had ~97% degradation efficiency of rhodamine B (RhB) dyes after 40 min irradiation. After five cycles of degradation, the degradation efficiency reduced to ~67%. The TiO2/g-C3N4 cement paste had superior degradation over RhB and methylene blue (MB). After five cycles of degradation, the photocatalytic cement paste still had higher efficiency, ~98% after 60 min degradation. A photocatalytic mechanism was proposed. TiO2/g-C3N4 powders and TiO2/g-C3N4 cement pastes can be one of highly promising photocatalysts for large-scale water treatment.