NiCo-layered double hydroxide/g-C3N4 heterostructures with enhanced adsorption capacity and photoreduction of Cr(VI)

Photo-catalytic reduction of highly toxic Cr(VI) using graphitic carbon nitride (g-C 3 N 4 ) based photocatalysts under visible light irradiation condition has been attracting considerable attention recent years. Here, we report the development of heterostructured NiCo-layered double hydroxides (LDHs) grown horizontally on g-C 3 N 4 nanosheets with different degrees of crystallinity (amorphous to crystalline), NiCoLDH/g-C 3 N 4 , with high photocatalytic activity for the reduction of toxic hexavalent chromium ions (Cr(VI)) as well as high adsorption capability for congo red (CR) photodegradation under visible light irradiation. The presence of NiCoLDH nanoparticles promotes the adsorption of the anionic pollutants while g-C 3 N 4 in the heterostructure promotes fast photodegradation of CR and reduction of Cr(VI). The NiCoLDH/g-C 3 N 4 composite prepared using amorphous-crystalline g-C 3 N 4 homojunctions shows the best adsorption performance. The kinetic data demonstrates improved correlation coefficient for the pseudo-second-order (R 2  > 0.99) and Freundlich isotherm model. The NiCoLDH/g-C 3 N 4 composite shows an improved separation efficiency of photogenerated electron and hole pairs, leading to its improved Cr(VI) adsorption and photo-reduction performance. The monolayer adsorption capacities of CR and Cr(VI) of the NiCoLDH/g-C 3 N 4 heterostructured composite can be as high as 1100 and 46 mg/g at 30 °C, respectively. This work provides new perspectives for the development of highly efficient g-C 3 N 4 -based composite photocatalysts for wastewater treatment related applications.