Photocatalytic H2 evolution over sulfur vacancy-rich ZnIn2S4 hierarchical microspheres under visible light

In this work, the sulfur vacancies were successfully introduced into the ZnIn2S4 (ZIS) lattice through two facile approaches, plasma etching and annealing, for enhancing the photocatalytic performance. The optimized plasma-etched ZIS exhibited an enhanced H-2 generation rate of 706 mu mol g(-1) h(-1), which was 5 and 1.2 times higher than that of pure ZIS and annealed ZIS, respectively. Theoretical calculation demonstrated that surface S vacancy could arouse the catalytic activity of the adjacent S atoms in inert (001) basal plane, serving as the active site for hydrogen evolution reaction (HER). Although annealing could produce much more S vacancies than the plasma etching, a majority of bulk S vacancies usually acted as charge recombination center to lower the photocatalytic activity. Hence, even plasma-etched ZIS presented poor light absorption capacity, plasma etching showed a better effect on the HER improvement of ZIS than annealing. This work presents a simple and promising pathway for optimization of 3D ZIS photocatalysts to improve photocatalytic hydrogen evolution.