Rationally designed MoS2/protonated g-C3N4 nanosheet composites as photocatalysts with an excellent synergistic effect toward photocatalytic degradation of organic pollutants.

The positively charged ultrathin g-C3N4 nanosheets are prepared by ultrasonic-assisted exfoliation of the protonated g-C3N4. Compared with the protonated g-C3N4 and exfoliated g-C3N4, the positively charged ultrathin g-C3N4 has abundant functional groups as well as desired dispersibility in deionized water, thus it could serve as a basic building block for designing related heterojunction composites. To take a full advantage of these features, the positively charged ultrathin g-C3N4/MoS2 composites are fabricated through a simple electrostatic adsorption and self-assembly process followed by a hydrothermal method. By loading an appropriate amount of MoS2 on the ultrathin g-C3N4 nanosheets, the as-fabricated composites exhibit considerable improvement on the photocatalytic activities toward the degradation of typical organic pollutants (i.e., methyl orange and phenol) under visible light irradiation. The composite containing 2 wt% MoS2 shows the highest efficiency of about 96.5% for the methyl orange degradation, which is about 3.5 times and 8 times compared to those of the positively charged ultrathin g-C3N4 and bulk g-C3N4, respectively. The superb photocatalytic performance benefits from the unique advantages, including richly available reaction sites, aligned energy levels between g-C3N4 and the MoS2, and efficient electron transfer. This work opens new possibilities for the rational design and construction of the g-C3N4 based composites as highly efficient and stable visible-light driven photocatalysts for the degradation of organic pollutants.