Hierarchical architectures of porous ZnS-based microspheres by assembly of heterostructure nanoflakes: Lateral oriented attachment mechanism and enhanced photocatalytic activity

Hierarchical ZnS-based microspheres with porous structures are successfully synthesized via a facile "one pot" route without using any templates or surfactants. These microspheres are aggregations composed of wurtzite/sphalerite heterostructure nanoflakes. Interestingly, due to the doping with In, the dipole field direction of ZnS-based nanoparticles changes. As a result, the formation of heterostructure nanoflakes are found to follow a lateral oriented attachment (LOA) mechanism and a subsequent phase transformation process rather than the oriented attachment (OA) mechanism reported in previous literatures. This discovery would provide a convenient method in constructing 2D anisotropic structures and might offer a new insight to the growth process of ZnS-based materials. Furthermore, photocatalytic activities for water splitting are investigated under visible-light irradiation (λ > 400 nm) and an enhanced photocatalytic activity (the initial rate for H ₂ evolution is up to 3.7 mmol h ^-1 with a concentration of photocatalyst of 45 mg L ^-1) is achieved, attributable to the particular heterostructure of 2D nanoflakes, the porous structure of 3D microspheres and the large specific area of as-prepared photocatalyst powders.