Mechanistic Insights into Anion-Induced Electrochromism of Ru(II)-Based Metallo-Supramolecular Polymer

Xiaofang Fu; Zhuohui Zhang; Zhenhu Cao; Alexandr Alexandrovich Rogachev; Maxim Anatolievich Yarmolenko; Tao Chen; Hongtao Cao; Hongliang Zhang

doi:10.3390/polym15244735

Mechanistic Insights into Anion-Induced Electrochromism of Ru(II)-Based Metallo-Supramolecular Polymer

Polymers (Basel). 2023 Dec 18;15(24):4735. doi: 10.3390/polym15244735.

Authors

Xiaofang Fu^{1

2}, Zhuohui Zhang^{1

3}, Zhenhu Cao⁴, Alexandr Alexandrovich Rogachev⁵, Maxim Anatolievich Yarmolenko⁶, Tao Chen¹, Hongtao Cao^{1

2}, Hongliang Zhang^{1

2}

Affiliations

¹ Laboratory of Advanced Nano Materials and Devices, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, China.
² Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China.
³ Nano Science and Technology Institute, University of Science and Technology of China, Suzhou 215123, China.
⁴ Ningbo Mi Ruo Electronic Technology Co., Ltd., Ningbo 315203, China.
⁵ Optical Anisotropic Films Laboratory, Institute of Chemistry of New Materials of the National Academy of Sciences of Belarus, 220141 Minsk, Belarus.
⁶ Department of Radiophysics and Electronics, Francisk Skorina Gomel State University, 104, Sovetskaya Street, 246019 Gomel, Belarus.

Abstract

The metallo-supramolecular polymer (MSP) is considered one of the most promising electrodes for electrochromic devices due to its intrinsically stable redox properties. Nevertheless, despite extensive work focusing on improving the electrochromic and electrochemical properties of MSPs, little experimental evidence exists from in-depth investigations on the anion-induced electrochromism of MSPs. Herein, Ru-based metallo-supramolecular polymer (polyRu) films with excellent electrochromic performance were fabricated through a novel electrochemical deposition method, and the electrochromic mechanism was further understood. The polyRu films possess fast reaction kinetics with a short switching time of 4.0 s (colored) and 2.8 s (bleached) and highly reversible redox properties due to the resulting impacts on the capacitive behaviors (containing surface, near-surface and intercalation pseudo-capacitance) of the perchlorate ions in the electrochromic process. Moreover, the electrochromic degradation of the polyRu films is considered to stem from the numerous nanopores in the film induced by ClO₄^- transport and the exchange of counter anions from Cl^- to ClO₄^-. In addition, a physical model, revealing the transport of conduction ions and the evolution of the structure and properties of the polyRu film during the electrochromic process, is presented. It is observed that the charge balance of Ru³⁺ and Ru²⁺, achieved through the adsorption/desorption of ClO₄^- on the film, provides electrochromic and electrochemical reversibility to the polyRu film under positive/negative bias. Correspondingly, a transformation from polyRu·(Cl^-)_2n to polyRu·(ClO₄^-)_x(Cl^-)_2n-x in the polyRu film is induced by a counter anion exchange from Cl^- to ClO₄^-. Revealing the detailed perchlorate ion transfer kinetics and electrochromic mechanism in this film can offer new insights into the application of metallo-supramolecular polymers in electrochromic devices.

Keywords: Ru(II)-based metallo-supramolecular polymer; anion-induced electrochromism; degradation mechanism; electrochromic film; kinetics of ion transport.

Grants and funding

2023H003/China Ningbo International Cooperation (China)