Monodispersed core/shell nanospheres of ZnS/NiO with enhanced H2 generation and quantum efficiency at versatile photocatalytic conditions

This investigation is first to elucidate the synthesis of mono-dispersed ZnS/NiO-core/shell nanostructures with a uniform thin layer of NiO-shell on the ZnS-nanospheres as a core under controlled thermal treatments. NiO-shell thickness varied to 8.2, 12.4, 18.2, and 24.2 nm, while the ZnS-core diameter remained stable about 96 +/- 6 nm. The crystalline phase and core/shell structure of the materials were confirmed using XRD and HRTEM techniques, respectively. Optical properties through UV-vis spectroscopy analysis revealed the manifestation of redshift in the absorption spectrum of core/shell materials, while the XPS analysis of elements elucidated their stable oxidation states in ZnS/NiO core/shell structure. The optimized ZnS/NiO-core/shell showed 1.42 times higher H2 generation (162.1 mmol h(-1) g(1)(cat)(-)) than the pristine ZnS-core (113.2 mmol h(-1) g(cat)(-1) ), and 64.5 times higher than the pristine NiO-shell (2.5 mmol h(-1) g(cat)(-1)). The quantum efficiency at wavelengths of 420, 365 nm, and 1.5 G air mass filters was found to be 13.5%, 25.0%, and 45.3%, respectively. Water splitting experiments was also performed without addition of any additives, which showed enhanced H-2 gas evolution of 1.6 mmol h(-1) g(cat)(-1) under the sunlight illumination. Photoelectrochemical measurements revealed the stable photocurrent density and minimized charge recombination in the system. The performed recyclability and reusability tests for five recycles demonstrated the excellent stability of the developed photocatalysts.

Automated summary

This study elucidated the synthesis of mono-dispersed ZnS/NiO-core/shell nanostructures with controlled thermal treatments, showing enhanced H2 generation and stable photocurrent density in water splitting experiments. The optimized ZnS/NiO-core/shell exhibited 1.42 times higher H2 generation compared to pristine ZnS-core and 64.5 times higher than pristine NiO-shell. Additionally, the developed photocatalysts demonstrated excellent stability in recyclability tests.