荆楚理工学院《JPS》：石墨烯/Ni(OH)2异质结，用于高性能混合超级电容器

成果简介

Ni(OH)2 作为超级电容器的电极材料很有前途，因为它具有优越的理论比电容，但其较差的循环稳定性仍然是一个障碍。本文，荆楚理工学院Liangzhe Chen等研究人员在《Journal of Power Sources》期刊发表名为“Rational design of hierarchical reduced graphene oxide/Ni(OH)2 heterojunction with long cycle life for high-performance hybrid supercapacitors”的论文，研究通过一种简便的静电自组装途径构建了还原氧化石墨烯（rGO）/Ni(OH)2 异质结，其中 Ni(OH)2 纳米片种植在 rGO 基底表面，从而增加了比表面积并加速了电子/离子传输，同时继承了 rGO 出色的循环稳定性。最佳的rGO/Ni(OH)2 电极在 2 A/g 时的比电容高达 2251.6 F/g，5000次循环后的循环稳定性高达104.9%。rGO/Ni(OH)2//活性炭混合超级电容器（HSC）在 775 W/kg 的条件下实现了 35.4 Wh/kg的出色能量密度，在 10,000 次循环后的循环耐久性达98.8%。此外，两个串联的HSC还能点亮27个并联的红色LED，持续时间超过210秒，展示了超级电容器的巨大应用前景。

图文导读

图1、(a) Schematic diagram of the preparation of rGO/Ni(OH)2 heterojunction; SEM images of (b) Ni(OH)2, (c) GO, (d) GO/Ni(OH)2 and (e) rGN-2; (f) digital photographs of Ni(OH)2, GO, GO/Ni(OH)2 and rGN solutions; (g) Zeta potential of Ni(OH)2 and GO.

图2、(a) XRD patterns of rGN-2, rGN-0, rGO, and Ni(OH)2; (b–c) TEM images; (d) HRTEM image; (e) selected area electron diffraction (SAED) pattern; and (f) elemental mapping images of rGN-2.

图3、 (a) Raman spectra of rGN-2, rGO and Ni(OH)2 (λ = 633 nm); XPS (b) survey spectrum and high-resolution spectra of (c) Ni 2p, (d) C 1s and (e) O 1s for rGN-2; (f) TG-DTA curves of various samples.

图4、(a) CV profiles and (b) GCD profiles of Ni(OH)2, rGO, rGN-1, rGN-2, and rGN-3 electrodes; (c) CV curves of the rGN-2 electrode at varied scan rates; (d) log |peak current| vs. log (sweep rate) and (e) contribution of capacitance and diffusion control for the rGN-2 electrode; (f) GCD curves of the rGN-2 electrode at varied current densities; (g) the corresponding specific capacity of different samples; (h) the cycling stability after 5000 cycles at 20 A/g; and (i) Nyquist plots of rGN-2 and Ni(OH)2 electrodes (illustration shows the corresponding equivalent circuit).

图5、 (a) Schematic diagram of ‘Swagelok’ cell; (b) CV curves of AC and rGN-2 at 30 mV/s; (c) CV curves of the rGN-2//AC HSC at different voltage windows; (d) CV curves at 550 mV/s; and (e) GCD curves at 1–10 A/g; (f) the calculated specific capacitance; (g) the Ragone plots of the HSC in comparison with previous works; (h) the cycling performance of the HSC device after 10,000 cycles at 10 A/g (illustration shows the corresponding HSC at initial and last five GCD cycles).

图6、 (a) CV curves at 30 mV/s (inset shows the corresponding circuit diagram) and (b) GCD curves of single and two HSCs connected in series at 1 A/g; (c) photograph of the tandem HSCs lighting up 27 red LEDs connected in parallel (2.5 V) for more than 210 s. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)

小结

通过合理的策略，从三维纳米球构建了分层 rGO/Ni(OH)2 异质结。通过简便的静电自组装和动态回流路线，α-Ni(OH)2纳米片生长在石墨烯基底上。在rGO上构建 Ni(OH)₂ 增强了比表面积（163.9 m2/g），加速了电子/离子传输，并继承了rGO出色的循环稳定性。因此，优化后的 rGO/Ni(OH)2电极在 2A/g条件下具有 2251.6F/g 的高比电容，在20A/g条件下，5000次循环后的循环稳定性高达 104.9%。经验证，电化学反应同时表现出电容控制和扩散控制行为。此外，在0-1.55V的工作电压下，rGO/Ni(OH)2//AC HSC 在 1A/g时具有104.5F/g的高比电容，在 775 W/kg 时具有 35.4 Wh/kg 的最大能量密度，在10A/g时经过 10,000 次循环后电容保持率达 98.8%。总之，这项研究为构建高性能分层 rGO/Ni(OH)2 异质结提供了合理的策略，为制备未来储能材料的新型复合材料铺平了道路。

文献：https://doi.org/10.1016/j.jpowsour.2024.235857