Effect of TiO2 crystal phase on the construction of TiO2/g-C3N4 heterojunction photocatalyst for efficient sunlight photodegradation of naphthalene

The effect of TiO 2 crystal phase on the photocatalytic properties of TiO 2 /g-C 3 N 4 heterojunction photocatalyst under sunlight irradiation was investigated through experiments and theoretical calculations. Results reveal that for TiO 2 /g-C 3 N 4 heterojunction photocatalyst, anatase phase TiO 2 can adjust the band edge positions to ensure the generation of strongly oxidizing radical species (·O 2- and ·OH), and rutile phase TiO 2 can effectively reduce the band gap to more efficiently utilize sunlight. Consequently, the combination of g-C 3 N 4 with P25 TiO 2 composed of both anatase and rutile phases is the most favorable combination for sunlight-driven photocatalyst among the obtained three TiO 2 /g-C 3 N 4 heterojunction photocatalyst. P25 TiO 2 and g-C 3 N 4 form a type-II/type-II heterostructure with stepped heterojunction and concave heterojunction. The P/CN photocatalyst exhibits excellent photocatalytic activity with degradation efficiencies for naphthalene reaching 100% within 120 min of sunlight irradiation, as well as considerable stability. The combination of P25 TiO 2 and g-C 3 N 4 has shown significant potentials in improving the separation and transfer efficiency of photogenerated electron-hole pairs, as well as enhancing the utilization of sunlight in photocatalytic process. This work provides a promising strategy for the preparation of highly active TiO 2 /g-C 3 N 4 heterojunction photocatalyst for the effective treatment of naphthalene from water.