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41. Hierarchical NiCo2Se4 Arrays Composed of Atomically Thin Nanosheets: Simultaneous Improvements in Thermodynamics and Kinetics for Electrocatalytic Water Splitting in Neutral Media.

Author

Chen, Hongyu, Xu, Yongsheng, Li, Xiaojie, Ma, Qing, Xie, Delong, Mei, Yi, Wang, Guojing, and Zhu, Yuanzhi

Subjects
THERMODYNAMICS, OXYGEN evolution reactions, HYDROGEN evolution reactions, NANOSTRUCTURED materials, ELECTROCATALYSTS, ELECTRONIC structure, PHOTOELECTROCHEMISTRY
Abstract

The inefficiency of electrocatalysts for water splitting in neutral media stems from a comprehensive impact of poor intrinsic activity, a limited number of active sites, and inadequate mass transport. Herein, hierarchical ultrathin NiCo2Se4 nanosheets are synthesized by the selenization of NiCo2O4 porous nanoneedles. Theoretical and experimental investigations reveal that the intrinsic hydrogen evolution reaction (HER) activity primarily originate from the NiCo2Se4, whereas the high oxygen evolution reaction (OER) performance is related to the NiCoOOH due to the structural reconstruction. The abundant Se and O vacancies introduced by atomically thin nanostructure modulate the electronic structure of NiCo2Se4 and NiCoOOH, thereby improving the intrinsic HER and OER activities, respectively. COMSOL simulation demonstrate the edges of extended nanosheets from the main body significantly promote the charge aggregation, boosting the reduction and oxidation current during HER/OER process. This charge aggregation effect notably exceeds the tip effect for the nanoneedle, highlighting the unique advantage of the hierarchical nanosheet structure. Benefiting from abundant vacancies and unique nanostructure, the hierarchical ultrathin nanosheet simultaneously improve the thermodynamics and kinetics of the electrocatalyst. The optimized samples display an overpotential of 92 mV for HER and 214 mV for OER at 100 mA cm−2, significantly surpassing the performance of currently reported HER/OER catalysts in neutral media. [ABSTRACT FROM AUTHOR]

Published
2024
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50. A Robust and Scalable N-Doped Carbon Coating Strategy for the High-Performance LiFePO4Cathode

Author

Xu, Hui, Feng, Dong, Li, Yi, Xie, Yuhui, Yang, Zhen, Wu, Feng, Mei, Yi, and Xie, Delong

Abstract

While the stable long-cycle performance of LiFePO4(LFP) cathodes holds significant promise for lithium-ion batteries (LiBs), their specific capacity and rate performance still fall short in market applications. In this study, we investigate surface modification of LFP using a cost-effective and highly conductive polyacrylonitrile (PAN)-induced carbon coating. Our findings indicate that 2 wt % of PAN can form a stable N–C layer on the surface of LFP particles, enhancing the Li+storage performance. Specifically, the initial discharge capacity reaches 153.9 mAh g–1at 0.5 C, with LFP-2 maintaining 148.8 mAh g–1after 150 cycles, significantly outperforming their counterparts LFP-0, LFP-1, and LFP-3. Under 1 C, the LFP-2 cathode exhibits an initial discharge specific capacity of 143.2 mAh g–1and excellent cycle stability, retaining 84.32% of its capacity after 500 cycles. Additionally, LFP-2 demonstrates stable rate performance at 0.1, 2, 4, 6, 8, and 10 C, delivering capacities of 159.4, 124.1, 110.6, 85.1, 73.0, and 62.5 mAh g–1, respectively. These results suggest that a uniform surface coating strategy could serve as an industrially scalable method for achieving a continuous carbon layer coating on other cathode materials.

Published
2024
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