A Molten Salt Strategy to Convert Bulk Nb2O5 Into 2D Nonlayered Niobium Nitride Nanosheets for Superior Pseudocapacitive Storage

en This link goes to a English section zh This link goes to a Chinese section Two-dimensional (2D) nonlayered niobium nitrides have attracted considerable interest for electrochemical energy storage. However, the synthesis of these materials is hampered by their nonlayered crystal structures, which are characterized by strong three-dimensional chemical bonding. Herein, we demonstrate the direct synthesis of nonlayered 2D NbN 0.8 /Nb 5 N 6 heterojunction nanosheets from commercial bulk Nb 2 O 5 through a scalable molten-salt-assisted route. The in situ formed molten KNbO 3 intermediate, confined within the K 2 CO 3 /KCl flux, guides the 2D growth of niobium nitride under NH 3 , yielding nanosheets with 4.8 nm thickness and lateral sizes of 3–5 μm. The as-synthesized 2D NbN 0.8 /Nb 5 N 6 nanosheets deliver a large capacitance of 918.2 F cm −3 (324.1 F g −1 ) at 1 A cm −3 , superior rate performance of 649.8 F cm −3 (229.4 F g −1 ) at 20 A cm −3 , and exceptional long-term cycling stability with 95.4% retention over 10,000 cycles, surpassing most reported niobium-based nitrides. Furthermore, the solid-state symmetric supercapacitor assembled with the two electrodes of 2D NbN 0.8 /Nb 5 N 6 nanosheets delivers a high volumetric energy density of 13 mWh cm −3 . This work reports a novel high-performance 2D niobium nitride electrode material and offers a generalizable synthesis strategy for 2D nonlayered transition metal nitrides. 摘要 en This link goes to a English section zh This link goes to a Chinese section 二维非层状氮化铌材料在电化学储能领域引起了广泛关注。然而,由于该类材料具有强三维化学键合的非层状晶体结构,其合成一直面临挑战。本研究展示了一种可规模化生产的熔盐辅助法,能够直接以商业块体Nb 2 O 5 为原料合成非层状二维NbN 0.8 /Nb 5 N 6 异质结纳米片。在NH 3 气氛下,原位生成并被限制在K 2 CO 3 /KCl熔盐介质中的KNbO 3 中间体,有效引导了材料的二维生长,最终获得了厚度为4.8 nm、横向尺寸为3–5 μm的纳米片。所合成的二维NbN 0.8 /Nb 5 N 6 纳米片在1 A cm −3 电流密度下具有918.2 F cm −3 (324.1 F g −1 )的高比电容,在20 A cm −3 下仍保持649.8 F cm −3 (229.4 F g −1 )的优异倍率性能,以及卓越的长循环稳定性(10,000次循环后容量保持率高达95.4%),其性能优于大多数已报道的铌基氮化物。此外,利用该二维NbN 0.8 /Nb 5 N 6 纳米片组装的固态对称超级电容器,可提供13 mWh cm −3 的高体积能量密度。本工作不仅报道了一种高性能的二维氮化铌电极材料,也为二维非层状过渡金属氮化物的合成提供了一种普适性策略。