Sahoo Ramesh Chandra, Sahoo Priyabrata, Mohanta Manish Kumar, Jena Puru, Matte H S S Ramakrishna
Energy Materials Laboratory, Centre for Nano and Soft Matter Sciences, Bangalore 562162, India.
Manipal Academy of Higher Education (MAHE), Manipal 576104, India.
Inorg Chem. 2024 Apr 29;63(17):7838-7847. doi: 10.1021/acs.inorgchem.4c00430. Epub 2024 Apr 18.
The exfoliation of nonlayered materials to mono- or few-layers is of growing interest to realize their full potential for various applications. Nickel cobaltite (NiCoO), which has a spinel crystal structure, is one such nonlayered material with unique properties and has been utilized in a wide range of applications. Herein, NiCoO is synthesized from NiCo- Layered double hydroxides using a topochemical conversion technique. Subsequently, bulk NiCoO is exfoliated into mono- or few-layer nickel cobaltene nanosheets using liquid-phase exfoliation in various low-boiling point solvents. An analytical centrifuge technique is also utilized to understand the solute-solvent interactions by determining their dispersion stability using parameters such as the instability index and sedimentation velocity. Among the studied solvents, water/isopropyl alcohol cosolvent is found to have better dispersion stability. In addition, density functional theory calculations are carried out to understand the exfoliation mechanism. It is found that the surface termination arising from the Co-O bond needs the least energy for exfoliation. Furthermore, the obtained nickel cobaltene nanosheets are utilized as an active material for supercapacitors without any conductive additives or binders. A solid-state symmetric supercapacitor delivers a specific capacitance of 10.2 mF cm with robust stability, retaining ∼98% capacitance after 4000 cycles.
将非层状材料剥离为单层或少数层以充分发挥其在各种应用中的潜力，这一研究正日益受到关注。具有尖晶石晶体结构的镍钴矿（NiCoO）就是这样一种具有独特性能的非层状材料，已被广泛应用于诸多领域。在此，采用拓扑化学转化技术由镍钴层状双氢氧化物合成了NiCoO。随后，在各种低沸点溶剂中通过液相剥离将块状NiCoO剥离成单层或少数层的镍钴烯纳米片。还利用分析离心技术，通过使用诸如不稳定指数和沉降速度等参数来确定溶质 - 溶剂相互作用的分散稳定性。在所研究的溶剂中，发现水/异丙醇共溶剂具有更好的分散稳定性。此外，进行了密度泛函理论计算以了解剥离机理。结果发现，由Co - O键产生的表面端基剥离所需能量最少。此外，所获得的镍钴烯纳米片无需任何导电添加剂或粘合剂即可用作超级电容器的活性材料。一种固态对称超级电容器的比电容为10.2 mF cm，具有强大的稳定性，在4000次循环后电容保持率约为98%。
