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Sulfurized polyacrylonitrile (S-cPAN) has been recognized as a particularly promising cathode material for lithium–sulfur (Li–S) batteries due to its ultra-stable cycling performance and high degree of sulfur utilization. Though the synthetic conditions and routes for modification of S-cPAN have been extensively studied, details of the molecular structure of S-cPAN remain yet unclear. Herein, a more reasonable molecular structure consisting of pyridinic/pyrrolic nitrogen (NPD/NPL) is proposed, based on the analysis of combined X-ray photoelectron spectroscopy, 13C/15N solid-state nuclear magnetic resonance, and density functional theory data. The coexistence of vicinal NPD/NPL entities plays a vital role in attracting S2 molecules and facilitating N–S bond formation apart from the generally accepted C–S bond in S-cPAN, which could explain the extraordinary electrochemical features of S-cPAN among various nitrogen-containing sulfurized polymers. This study provides new insights and a better understanding of structural details and relevant bond formation mechanisms in S-cPAN, providing a foundation for the design of new types of sulfurized cathode materials suitable for application in next-generation high-performance Li–S batteries.

An understanding of the interaction of water with perovskite is crucial in improving stability. In this study, the structural and electronic properties of γ-CsPbI3(220) perovskite surface upon the water molecules adsorption are presented.

A counter electrode (CE), which acts as an efficient catalyst, plays a pivotal role in dye-sensitized solar cells (DSSCs). Graphene doped by heteroatoms has been regarded as a material having a high reduction catalytic activity to develop efficient Pt-free alternative CE. However, the doping effects accounting for such a catalytic activity remain unknown. In this study, by means of density functional theory calculations, we determined the band gaps, formation energies, and regions of chargeinduced impurities to examine the possibilities of B-doped, N-doped, and B−N co-doped graphene (BNG) sheets to replace platinum as CE. Our results demonstrated that the B−N co-doped graphene (BNG) is suitable to be used for CE owing to its small band gap, small formation energy, and having appropriate region of charge-induced impurities. In addition, we considered the iodide reduction reaction on the negatively charged BNG sheet. After injecting two extra electrons, the I 2 molecule can strongly adsorb on the BNG surface and the I 2 decomposition can be achieved with a small activation energy. A theoretical analysis of the obtained results provides us with some useful guidelines for identifying low-cost and effective CEs in the DSSC devices.