Regular study of lanthanide oxides for boosting photocatalytic hydrogen production on ZnIn2S4 photocatalysts

Lanthanide oxides have potential advantages for photocatalytic hydrogen production . To systematically investigate the photocatalytic performance of lanthanide oxides on metal sulfides , a series of Ln x O y /ZnIn 2 S 4 (Ln x O y /ZIS) were synthesized by hydrothermal method . Comprehensive characterization demonstrated that Ln x O y synergistically improved the performance of ZnIn 2 S 4 by extending light absorption, reducing contact interface resistance and enhancing carrier separation. The photocatalytic hydrogen evolution (PHE) rates of the Ln x O y /ZIS photocatalysts were improved, which were 1.6–4.2 times higher than those of pure ZnIn 2 S 4 (198.0 μmol g −1 h −1 ). The PHE rates of Ln x O y /ZIS decreased with increasing lanthanide atomic number, and when the lanthanides contained variable valence ions, the PHE rates of Ln x O y /ZIS were superior to those of neighbouring lanthanides. The heterojunction formed by Ln x O y and ZnIn 2 S 4 effectively promoted carrier separation. Lanthanide ions with unoccupied 4 f orbital were more likely to accept electrons and served as a hydrogen adsorption site for further hydrogen reduction. Multivalent ions could also promote the migration of electrons and generate oxygen vacancies to inhibit the recombination of carriers. In conclusion, for ZnIn 2 S 4 , lanthanide oxides are promising candidates to improve the performance of PHE. This study provides guidance on the selection of appropriate lanthanide oxides for the construction of efficient sulphur-based heterojunction photocatalysts.