Transition metal oxide-based electrochromic materials for energy-saving fenestration and smart energy storage devices

Abstract

Electrochromism is an electrochemical phenomenon where the optical properties of the materials change reversibly and persistently with the externally applied voltages. It has received increasing attention due to its intriguing features and tremendous applications in electronic displays, energy-efficient fenestrations in buildings and smart energy storage devices.[1] In 21st century, with the rising need for energy saving, alternative sources of energy and automated electronic devices with smart features, both smart windows and smart energy storage devices are going to be an indispensable part of future world. Among potential electrochromic materials transition metal oxides (TMOs) have received immense attention from researchers due to their natural abundance and excellent stability. However, they often exhibit poor performance issues such as low optical contrast, low coloration efficiency and slow color switching speeds, majorly due to their inadequate electrical conductivity.[2] Nanostructured TMOs help to overcome these issues to some extent as their high surface to volume ratio can reduce charge diffusion distances. In commensuration with the recent research works, the main objective of this thesis is to develop TMO nanostructures with significantly improved performance metrics and subsequently integrate these TMO nanostructures to build functional electrochromic smart windows and smart energy storage devices. To start with, anodically coloring NiO is chosen to demonstrate how its electrochromic performance can be boosted by varying its electrochemically accessible surface area. Further, the material is used to fabricate a polymeric gel electrolyte-based prototype device for smart window application.[3] In the next part of the thesis, metal organic framework (MOF) derived carbon embedded porous NiO is synthesized, which is capable of showing better electrochromic performance compared to the prior one. The material is subsequently integrated as a smart positive electrode to construct a rechargeable ZnNiO electrochromic battery, which demonstrates its state of charge by changing the colour from dark brown (charged) to transparent (discharged).[4] However, the color change, in this case, is monochromatic and in context of the smart energy storage, it is always desirable to have several shades of color to have precise knowledge about the state of charge of energy storage devices. Hence, in the final chapter of this thesis, V2O5 is chosen owing to its capability to show both cathodic and anodic coloration. MOF-derived porous V2O5 is eventually integrated to a functional multicolored electrochromic asymmetric supercapacitor device with electrochromic polyaniline as the positive electrode.[5]

References

1. R. J. Mortimer, D. R. Rosseinsky, P. M. S. Monk (Eds.), Electrochromic Materials and Devices, Wiley-VCH, Weinheim, Germany, 2015. 2. H. Liang, R. Li, C. Li, C. Hou, Y. Li, Q. Zhang, H. Wang, Regulation of carbon content in MOF-derived hierarchical-porous NiO@C films for high-performance electrochromism. Materials Horizons 2019, 6 (3), 571-579 3. A. Dewan, S. Haldar, R. Narayanan, Multi-shelled NiO hollow microspheres as bifunctional materials for electrochromic smart window and non-enzymatic glucose sensor. Journal of Solid State Electrochemistry 2021, 25 (3), 821-830 4. A. Dewan, S. Sur, R. Narayanan, Musthafa O. T., MOF-Derived Carbon Embedded NiO for an Alkaline Zn−NiO Electrochromic Battery. ChemElectroChem, 2022, 9, e202200001 5. A. Dewan, R. Narayanan, M. O. Thotiyl, A multi-chromic supercapacitor of high coloration efficiency integrating a MOF-derived V2O5 electrode, Nanoscale, 2022, 14, 17372-17384