Enhanced hydrogen production from water over Ni doped ZnIn ₂S₄ microsphere photocatalysts

Ni²⁺ doped ZnIn₂S₄ microsphere with flower-like nanoscale petals were prepared by a hydrothermal method. There was an optimal Ni doping content of 0.3 wt% where hydrogen production reached the maximum. Higher Ni²⁺ doping can hardly dope into the ZnIn ₂S₄ lattice and just stay at ZnIn₂S₄ surface, leading to decreased activity. It was determined that Ni²⁺ entering the ZnIn₂S₄ lattice instead of surface NiS dominated the enhanced photocatalytic activity. The experimental results were rationalized by assuming Ni²⁺ serving as shallow trapping sites, greatly enhancing the activity of the photocatalyst. Graphical Abstract: Ni ²⁺ doped ZnIn₂S₄ microsphere with flower-like nanoscale petals were prepared by a hydrothermal method. There is an optimal Ni doping content of 0.3 wt% where hydrogen production reached the maximum. It is assumed that Ni²⁺ serving as shallow trapping sites can separate the arrival time of e^-/h⁺ pairs at the petal surface of ZnIn₂S₄, so as to greatly reduce their surface recombination and which, in turn, leads to improved hydrogen production.