NiPS3Intercalates as Catalysts for the Oxidation of Sulfide Ions: Synthesis, Catalytic Activity, and XPS Study

Abstract

Several intercalates of layered NiPS3have been synthesized by reaction of this compound with aqueous solutions of sodium sulfide and subsequent cation exchange or polymer insertion. The catalytic efficiency of these intercalates for the oxydation of sulfide ions into elemental sulfur by dioxygen has been studied. Results show that these intercalates have a greater efficiency than pristine NiPS3(higher reaction rate, smaller activation energy, suppression of any induction period). The electronic structure of the intercalates has been studied mainly by XPS of the Ni, P, and S atoms. Although the chemistry accompanying the intercalation processes appears complex (small losses of phosphorus, appearance of phosphate, and thiophosphate PS43−species), the catalytic efficiency of the intercalates is correlated to their ability to be reduced in depth when brought in contact with aqueous sodium sulfide. Our results are consistent with a previously suggested catalytic mechanism based on sequences of intercalation/deintercalation processes of sodium ions associated to redox modifications of the host lattice.