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

The positively charged ultrathin g-CN nanosheets are prepared by ultrasonic-assisted exfoliation of the protonated g-CN. Compared with the protonated g-CN and exfoliated g-CN, the positively charged ultrathin g-CN 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-CN/MoS composites are fabricated through a simple electrostatic adsorption and self-assembly process followed by a hydrothermal method. By loading an appropriate amount of MoS on the ultrathin g-CN 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% MoS 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-CN and bulk g-CN, respectively. The superb photocatalytic performance benefits from the unique advantages, including richly available reaction sites, aligned energy levels between g-CN and the MoS, and efficient electron transfer. This work opens new possibilities for the rational design and construction of the g-CN based composites as highly efficient and stable visible-light driven photocatalysts for the degradation of organic pollutants.