NIPS3 INTERCALATES AS CATALYSTS FOR THE OXIDATION OF SULFIDE IONS - SYNTHESIS, CATALYTIC ACTIVITY, AND XPS STUDY

Several intercalates of layered NiPS3 have been synthesized by reactio n of this compound with aqueous solutions of sodium sulfide and subseq uent cation exchange or polymer insertion. The catalytic efficiency of these intercalates for the oxydation of sulfide ions into elemental s ulfur by dioxygen has been studied. Results show that these intercalat es 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 X PS of the Ni, P, and S atoms. Although the chemistry accompanying the intercalation processes appears complex (small losses of phosphorus, a ppearance of phosphate, and thiophosphate PS43- species), the catalyti c 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 mecha nism based on sequences of intercalation/deintercalation processes of sodium ions associated to redox modifications of the host lattice. (C) 1997 Academic Press.