context: To probe the surface chemistry of MoS2 NDs before and after LPS adsorption, XPS measurements were carried out. Fig. S7 (ESI†) shows the deconvoluted Mo 3d and S 2p spectra of the pristine and polysulfides-mixed MoS2 NDs. In comparison with the pristine MoS2 NDs, the Mo 3d peaks of 3d3/2 and 3d5/2 for the MoS2 ND/polysulfide were overall downshifted by ∼0.15 eV, which could be attributed to the intense interaction of the exposed Mo atoms with the surrounding strong electronegative sulfur ligand. In the S 2p spectra, peaks centered at 163.2, 162.6, and 161.3 eV, corresponding to the S 2p1/2 and 2p3/2 components of the original MoS2 ND, were almost intact after mixing with the polysulfides, possibly due to the weak interaction between the S atoms in the MoS2 NDs and polysulfides. Interestingly, new features located at 159.8 and 165.2–169.4 eV appeared for the MoS2 ND/polysulfide, which were considered due to the formation of the polythionate moiety. It is reasonable to deduce that the “sulfiphilic” surface for MoS2 NDs would significantly promote the retention of polysulfides in the cathode region. More importantly, the edge-rich MoS2 NDs increased the Mo–S bridge between the metallic catalyst and polysulfides, propelling electron transfer across the MoS2 NDs to the polysulfides, and thus significantly catalyzing the chemical redox conversion of the polysulfides.
answer: MoS2 NDs