Yanshan University

About: Yanshan University is a education organization based out in Qinhuangdao, China. It is known for research contribution in the topics: Microstructure & Control theory. The organization has 19544 authors who have published 16904 publications receiving 184378 citations. The organization is also known as: Yānshān dàxué.

Unraveling the Reaction Mechanism of FeS2 as a Li-Ion Battery Cathode.

Abstract: Iron pyrite (FeS2) is a promising lithium-ion battery cathode material because of its low cost and ultrahigh energy density (1671 Wh kg-1). However, its reaction mechanisms are still controversial. In this work, we find that different from the conventional belief that an intermediate phase Li2FeS2 is formed followed by Fe/Li2S composites at the initial discharge, it undergoes a one-step reaction (FeS2 → Fe + Li2S) or a two-step reaction (FeS2 → FeS + Li2S → Fe + Li2S), which depends on the current rate and temperature. In the charge process, it undergoes a two-step reaction: phase transition Fe + Li2S → FeS at about 1.74 V and generation of elemental sulfur (Li2S → S, 2.30 V). FeS is a mackinawite phase that is formed on the interface of Li2S via heteroepitaxial growth. Subsequent cycles involves a combination reaction of FeS and S. The reaction mechanism suggests that FeS2 suffers from the demerits of both FeS and S, such as a large volume change, voltage hysteresis, and polysulfide dissolution. These findings would help us to understand the intrinsic capacity fading of FeS2 and provide guidelines to improve its electrochemical performances.

Structure of the Au23-xAgx(S-Adm)(15) Nanocluster and Its Application for Photocatalytic Degradation of Organic Pollutants

Abstract: Ligands play an important role in determining the atomic arrangement within the metal nanoclusters. Here, we report a new nanocluster [Au23-xAgx(S-Adm)(15)] protected by bulky adamantanethiol ligands which was obtained through a one-pot synthesis. The total structure of [Au23-xAgx(S-Adm)(15)] comprises an Au13-xAgx icosahedral core, three Au-3(SR)(4) units, and one AgS3 staple motif in contrast to the 15-atom bipyramidal core previously seen in [Au23-xAgx(SR)(16)]. UV/Vis spectroscopy indicates that the HOMO-LUMO gap of [Au23-xAgx(S-Adm)(15)] is 1.5 eV. DFT calculations reveal that [Au19Ag4(S-Adm)(15)] is the most stable structure among all structural possibilities. Benefitting from Ag doping, [Au23-xAgx(S-Adm)(15)] exhibits drastically improved photocatalytic activity for the degradation of rhodamine B (RhB) and phenol under visible-light irradiation compared to Au-23 nanoclusters.