▲ Vol 39 Issue 39 | 03  October , 2023

Operando Imaging of Over-Discharge-Induced Surface Morphology Evolutions of LiMn2O4 Submicron-Sized Particles by Electrochemical High-Speed Atomic Force Microscopy

Peifa Yang, Zhuanfang Bi, and Guangyi Shang

Spinel LiMn2O4 is a promising cathode material but suffers from severe capacity fading during battery operation. One of capacity fade mechanisms results from changes in its morphology and structure due to over-discharge. In this work, for the first time, we successfully tracked the morphologic evolution of LiMn2O4 submicron-sized particles during over-discharging by our home-made electrochemical high-speed atomic force microscopy (EC-HS-AFM). Seven hundred and sixty successive EC-HS-AFM images were stably captured at an imaging speed of ∼0.85 fps at corresponding potentials during over-discharging in ∼15 min, from which evolutions of nanoscale wrinkle-like and step-like structures on the particle surface were clearly observed. The phenomena could be resulted from the complex stresses due to structural distortion during the phase transformation from cubic (LiMn2O4) to tetragonal (Li2Mn2O4), and the formation of the Li2Mn2O4 phase was confirmed by ex situ XRD. Moreover, the particle surface area as a function of the potential was quantitatively extracted from the EC-HS-AFM images, revealing the irreversible expansion/contraction of the particles, and this finding obtained at the nanoscale was consistent with the macroscopic results tested by cyclic voltammetry and galvanostatic charge/discharge methods. These results demonstrate that the EC-HS-AFM is a powerful tool to establish the correlation between the over-discharge-induced surface morphology changes and irreversibility of the Li-ion insertion/extraction as well as capacity fading.

https://pubs.acs.org/doi/10.1021/acs.langmuir.3c01126

▲ Vol 145 Issue 39 | 04  October , 2023

Carbon-Bonding Metal Catalysis (CBMC): A Supramolecular Complex Directs Structural-Isomer Selection in Gold-Catalyzed Reactions

Xinxin Li, Lingfei Hu, Gang Lu, and Yao Wang

Spinel LiMn2O4 is a promising cathode material but suffers from severe capacity fading during battery operation. One of capacity fade mechanisms results from changes in its morphology and structure due to over-discharge. In this work, for the first time, we successfully tracked the morphologic evolution of LiMn2O4 submicron-sized particles during over-discharging by our home-made electrochemical high-speed atomic force microscopy (EC-HS-AFM). Seven hundred and sixty successive EC-HS-AFM images were stably captured at an imaging speed of ∼0.85 fps at corresponding potentials during over-discharging in ∼15 min, from which evolutions of nanoscale wrinkle-like and step-like structures on the particle surface were clearly observed. The phenomena could be resulted from the complex stresses due to structural distortion during the phase transformation from cubic (LiMn2O4) to tetragonal (Li2Mn2O4), and the formation of the Li2Mn2O4 phase was confirmed by ex situ XRD. Moreover, the particle surface area as a function of the potential was quantitatively extracted from the EC-HS-AFM images, revealing the irreversible expansion/contraction of the particles, and this finding obtained at the nanoscale was consistent with the macroscopic results tested by cyclic voltammetry and galvanostatic charge/discharge methods. These results demonstrate that the EC-HS-AFM is a powerful tool to establish the correlation between the over-discharge-induced surface morphology changes and irreversibility of the Li-ion insertion/extraction as well as capacity fading.

https://pubs.acs.org/doi/10.1021/jacs.3c07551

▲ Vol 07 Issue 20 | 21 October , 2023

Recent progress in metal halide perovskite photocatalysts for hydrogen evolution

Xing Wang, Yu Peng, Shuang Yang, Hua Gui Yang and  Yu Hou

Photocatalytic hydrogen production, which directly converts solar energy into green chemical fuel, has received widespread attention. However, despite significant efforts, the efficiency of conventional photocatalytic materials remains below industrial requirements, owing to the intrinsic limitations such as insufficient light absorption and poor carrier transport capability. Metal halide perovskite (MHP) materials feature superior optoelectronic properties and structural flexibility, rendering them highly attractive candidates for photocatalysis. This review provides a concise introduction to the structural characteristics of MHPs and summarizes their recent progress in the field of photocatalytic hydrogen evolution, including single-component MHPs and MHP-based composites. The review also discuss the current challenges and prospects of MHP photocatalysts, which hold promise for advancing photocatalytic solar-to-hydrogen technology.

https://pubs.rsc.org/en/content/articlelanding/2023/qm/d3qm00477e

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静远嘲风（MY Scimage） 成立于2007年，嘲风取自中国传统文化中龙生九子，子子不同的传说，嘲风为守护屋脊之瑞兽，喜登高望远；静远取自成语“宁静致远”，登高莫忘初心，远观而不可务远。

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