A ternary photocatalyst of graphitic carbon nitride/cadmium sulfide/titania based on the electrostatic assembly using two-dimensional semiconductor nanosheets.

Herein, we employed the exfoliated two-dimensional (2D) graphitic carbon nitride nanosheets (CNNS) and titania nanosheets (TNS) as building blocks, and these negatively charged nanosheets were flocculated by Cd ions with a followed sulfidation treatment to produce a ternary heterostructure photocatalyst of CNNS/CdS/TNS. This novel nanocomposite exhibited outstanding absorption in visible spectral region, and meanwhile its gradient band structure and the closed interface promoted the separation of photo-generated charge. The relative content of CNNS and TNS in the ternary nanocomposite was optimized, and the optimal photocatalyst with a CNNS/TNS mass ratio of 98:2 could rapidly remove 10mgL rhodamine B (RhB) in 20min under visible light irradiation. The calculated rate constant of CNNS/CdS/TNS was 56.87, 12.18, and 6.67 times higher than those of the restacked CNNS and TNS and the individual CdS, as well as 8.31, 6.22 and 2.57 times higher than those of binary CNNS/TNS, CdS/TNS and CdS/CNNS photocatalysts, respectively. Moreover, this nanocomposite possessed a superior durability and universality for degradation of RhB in different concentration and other organic pollutants, including dyes and colorless compounds. Finally, the possible photocatalytic mechanism was proposed based on the theoretical calculation and the active species quenching experiment.