Facile construction of Z-scheme g-C3N4/BiVO4 heterojunctions for boosting visible-light photocatalytic activity

•Assembly of g-C3N4 nanosheets and BiVO4 hollow spheres in a large scale.•Improved dispersion of BiVO4 hollow spheres on the lamellar surface of g-C3N4 nanosheets.•Enhanced visible light photocatalytic properties of g-C3N4/BiVO4.•The Z-scheme degradation pathways of MO removal. Photocatalytic technology is one of the effective methods to treat the azo dye wastewater that has posed a serious threat to human environment and health. Composed of graphitic carbon nitride (g-C3N4) nanosheets and BiVO4 hollow spheres, the g-C3N4/BiVO4 composites were successfully assembled by thermal treatment. The uniform BiVO4 hollow spheres were more evenly scattered on the layered structure of g-C3N4 nanosheets, inhibiting the aggregation of nanoparticles. The confirmed g-C3N4/BiVO4 heterojunctions facilitate the transfer and separation of charges. Compared with g-C3N4 nanosheets and BiVO4 hollow spheres, the optimized g-C3N4/BiVO4 composite exhibits the significantly enhanced photocatalytic performance, owing to the formation of the heterojunctions, high charge separation efficiency and strong redox ability. The Z-scheme mechanism over the composite has been proposed to reveal the pathway of separation and transfer of the photo-generated charges in the MO degradation. The g-C3N4/BiVO4 heterojunctions with hollow porous structures could effectively enhance the photocatalytic degradation of pollutants.