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11. Equivalent Circuit Model Recognition of Electrochemical Impedance Spectroscopy via Machine Learning

Author

Zhu, Shan, Sun, Xinyang, Wang, Yuxuan, Zhao, Naiqin, and Sha, Junwei

Subjects
Physics - Data Analysis, Statistics and Probability, Physics - Applied Physics, Physics - Computational Physics
Abstract

Electrochemical impedance spectroscopy (EIS) is an effective method for studying the electrochemical systems. The interpretation of EIS is the biggest challenge in this technology, which requires reasonable modeling. However, the modeling of EIS is of great subjectivity, meaning that there may be several models to fit the same set of data. In order to overcome the uncertainty and triviality of human analysis, this research uses machine learning to carry out EIS pattern recognition. Raw EIS data and their equivalent circuit models were collected from the literature, and the support vector machine (SVM) was used to analyze these data. As the result, we addresses the classification of EIS and recognizing their equivalent circuit models with accuracies of up to 78%. This study demonstrates the great potential of machine learning in electrochemical researches.

Published
2019

16. Multi-scale synergistic regulation of hierarchical porous Ni@NiSe cathodes with low voltage gap, high capacity and long-term cycling stability in Li–CO2 battery.

Author

Shi, Yating, Xie, Haonan, Ma, Liying, Chen, Biao, Kang, Jianli, Shi, Chunsheng, He, Chunnian, and Sha, Junwei

Subjects
LOW voltage systems, ELECTRONIC band structure, CATHODES, ELECTRIC batteries, LITHIUM cells, ENERGY consumption, METAL-air batteries
Abstract

The Li–CO2 battery often suffers from high overpotential and limited capacity due to the challenges associated with the adsorption of Li+ and CO2 and the decomposition of Li2CO3. Herein, hexagonal rich-stepped NiSe crystals are in situ achieved on a three-dimensional (3D) free-standing porous Ni skeleton with double continuous channel architecture (namely p-Ni@NiSe-50) through an in situ selenization process. Structural characterization and theoretical calculation are applied to demonstrate the synergistic effects of marco/microstructural design and electronic band structure regulation. As a result, the adsorption/desorption of Li+ and CO2 and the formation/decomposition of Li2CO3 are effectively promoted, simultaneously, enabling an enhanced capacity and reversibility of p-Ni@NiSe-50 as the cathode of Li–CO2 battery. An ultra-low overpotential of 0.46 V and a remarkably high energy efficiency of 83.8% (20 μA cm−2) are achieved, along with a high full discharge specific capacity of 8844 μAh cm−2. Excellent long-term cycling stability (cycles up to 1000 h at a voltage gap of 1.14 V) of p-Ni@NiSe-50 is also obtained. The results of this work would provide a new insight and strategy to develop high-performance alkali metal-air batteries. Multi-scale synergistic effect of combining the cathode macroscopic structure design and the microscopic band structure design of NiSe was demonstrated to promote the adsorption of Li+ and CO2, as well as the decomposition of Li2CO3, so as to achieve ultra-low voltage gap and high capacity of Li-CO2 batteries. [ABSTRACT FROM AUTHOR]

Published
2024
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37. Balancing Strength and Ductility in Al Matrix Composites Reinforced by Few-Layered MoS 2 through In-Situ Formation of Interfacial Al 12 Mo.

Author

Fan, Lewen, Yang, Lizhuang, Zhao, Dongdong, Ma, Liying, He, Chunnian, He, Fang, Shi, Chunsheng, Sha, Junwei, and Zhao, Naiqin

Subjects
ALUMINUM composites, METALLIC composites, POWDER metallurgy, DUCTILITY, INTERFACIAL bonding, GRAIN refinement
Abstract

In this work, few-layered MoS2 (FLM) nanosheet-reinforced Al matrix composites are developed through powder metallurgy and hot extrusion. The microstructure, mechanical properties, and strengthening mechanisms have been systematically investigated. It is found that Al12Mo and Al2S3 can be formed in-situ during the sintering process, resulting in the improvement of interfacial bonding between FLM and Al matrix. With 1.5 wt.% of FLM addition, an improved tensile strength of 234 MPa with a high elongation of 17% can be obtained. Moreover, the strengthening mechanisms are also demonstrated to be grain refinement, dislocation strengthening, and load transfer, and the calculation indicates that load transfer is the main contribution factor. This work will inspire more new designs of metal matrix composites with balanced strength and ductility. [ABSTRACT FROM AUTHOR]

Published
2021
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38. Single-Atomic Ruthenium Catalytic Sites on Nitrogen-Doped Graphene for Oxygen Reduction Reaction in Acidic Medium

Author

Qifeng Zhong, Haisheng Yu, Xiaolong Zou, Junwei Sha, Emilie Ringe, Zheng Jiang, James M. Tour, Mingjie Liu, Naiqin Zhao, Sadegh Yazdi, Chenhao Zhang, Dongliang Chen, Boris I. Yakobson, Juncai Dong, Jibo Zhang, Huilong Fei, Sha, Junwei [0000-0002-5211-8663], Jiang, Zheng [0000-0002-0132-0319], Tour, James M [0000-0002-8479-9328], and Apollo - University of Cambridge Repository

Subjects
inorganic chemicals, Inorganic chemistry, Oxide, General Physics and Astronomy, chemistry.chemical_element, 02 engineering and technology, 010402 general chemistry, Photochemistry, Electrocatalyst, nitrogen-doped graphene oxide, 01 natural sciences, electrocatalysts, Catalysis, law.invention, chemistry.chemical_compound, law, General Materials Science, atomically dispersed ruthenium, oxygen reduction reaction, Graphene, General Engineering, 021001 nanoscience & nanotechnology, Electrochemical energy conversion, 0104 chemical sciences, Ruthenium, chemistry, Reversible hydrogen electrode, Methanol, 0210 nano-technology
Abstract

The cathodic oxygen reduction reaction (ORR) is essential in the electrochemical energy conversion of fuel cells. Here, through the NH3 atmosphere annealing of a graphene oxide (GO) precursor containing trace amounts of Ru, we have synthesized atomically dispersed Ru on nitrogen-doped graphene that performs as an electrocatalyst for the ORR in acidic medium. The Ru/nitrogen-doped GO catalyst exhibits excellent four-electron ORR activity, offering onset and half-wave potentials of 0.89 and 0.75 V, respectively, vs a reversible hydrogen electrode (RHE) in 0.1 M HClO4, together with better durability and tolerance toward methanol and carbon monoxide poisoning than seen in commercial Pt/C catalysts. X-ray adsorption fine structure analysis and aberration-corrected high-angle annular dark-field scanning transmission electron microscopy are performed and indicate that the chemical structure of Ru is predominantly composed of isolated Ru atoms coordinated with nitrogen atoms on the graphene substrate. Furthermore, a density function theory study of the ORR mechanism suggests that a Ru-oxo-N4 structure appears to be responsible for the ORR catalytic activity in the acidic medium. These findings provide a route for the design of efficient ORR single-atom catalysts.

Published
2017

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