Coordination Complex Transformation-Assisted Fabrication for Hollow Chestnut-Like Hierarchical ZnS with Enhanced Photocatalytic Hydrogen Evolution

Hierarchical nanostructures (HNs) are possibly endowed with novel properties due to their complex three-dimensional (3D) structures. Here, we provide a novel stepwise growth strategy of Coordination Complex Transformation-Assisted Growth for fabricating HNs. By using this, we prepare a new wurtzite ZnS HNs-hollow chestnut-like hierarchical microspheres (HCHMs), which are mesoporous hollow microspheres with single crystalline nanorods arrayed densely and radially from the centre. The HCHMs formation depends on the stepwise decomposition of the two Zn2+ complexes ([Zn(en)m(H2O)2(3−m)]2+ and [Zn(en)m(NH3)2(3−m)]2+, natural number m < 3). As the reaction proceeds, [Zn2+] has been distinctly reduced due to the transformation from [Zn(en)m(H2O)2(3−m)]2+ to [Zn(en)m(NH3)2(3−m)]2+ with a high stability constant, leading to a low crystal growth rate to obtain single crystalline nanorods. Additionally, the generated bubbles (CO2, NH3) acting as a template can induce the generation of hollow structure. The as-prepared ZnS HCHMs show an enhanced photocatalytic hydrogen evolution activity due to the single crystalline wurtzite phase and the high surface area contributed by the hollow hierarchical structures, as well as the mesoporosity. The versatility of the coordination complex transformation-assisted growth strategy will open up new possibilities for fabricating HNs, especially for those transition metal ions with excellent complex capabilities.