image: Researchers designed a hybrid material made of titanium dioxide (TiO₂) and custom viologen molecules (TGP) that can both store energy and change color. The TiO₂ layer provides a stable scaffold for storing zinc ions, while the TGP molecules attached through strong chemical bonds enable vivid, reversible color switching. As the device charges from 0 to 1 volt, it gradually changes from deep magenta to light yellow — a visible indicator of its energy level. This smart electrochromic design bridges energy storage and visual display, allowing users to “see” how much energy remains in real time.
Credit: Prof. Yanhong Tian from Harbin Institute of Technology, Dr. Lizhi Xu from The University of Hong Kong, and Dr. Yanqing Tian from Southern University of Science and Technology, China
Scientists from Harbin Institute of Technology, together with collaborators from The University of Hong Kong and Southern University of Science and Technology, has developed a decoupled titanium dioxide–viologen hybrid material that integrates energy storage and color-changing display functions within a single system. This breakthrough enables high-capacity, high-efficiency electrochromic energy storage and marks an important step toward the next generation of smart, interactive energy devices.
Electrochromic energy storage devices (EESDs) can visually display their charge–discharge state by changing color during operation. However, conventional materials struggle to balance color performance and energy storage due to strong coupling between electrochromic and redox processes. The new study addresses this challenge by decoupling the optical and electrochemical behaviors through molecular and interfacial design.
Innovative Hybrid Design
The team constructed a TiO₂/viologen-derivative (TiO₂/TGP) hybrid electrode using phosphate–titanium (P–O–Ti) linkages to form a stable chemical interface. In this architecture, TiO₂ serves as the inorganic backbone for Zn²⁺ ion storage, while the viologen derivative (TGP) undergoes reversible electron transfer to achieve color modulation.This decoupled system effectively eliminates interference between energy storage and coloration, resulting in enhanced stability and performance.
The hybrid material achieved an optical modulation of 54%, coloration efficiency of 512.93 cm²/C, and an areal capacity of 62.2 mAh/m² in aqueous Zn²⁺ electrolyte, maintaining stable operation over 3,000 charge–discharge cycles. By introducing a thiophene group into the TGP molecule, the team successfully tuned its electronic band gap and suppressed radical dimerization, producing vivid magenta coloration and excellent cycling durability.
Toward Smart and Visual Energy Systems
This research provides a new strategy for building multifunctional energy systems that merge visual interactivity with energy storage.
“These hybrid materials open the door to flexible and intelligent energy devices that can visually indicate their energy state,” said Dr Zhang. “Such systems could find applications in smart windows, wearable electronics, and self-powered information displays.” The study also highlights the potential of eco-friendly and scalable fabrication, offering a pathway toward flexible, multi-color, and integrable visual energy platforms for future smart and sustainable technologies.
About Research Journal
Launched in 2018, Research is the first journal in the Science Partner Journal (SPJ) program. Research is published by the American Association for the Advancement of Science (AAAS) in association with Science and Technology Review Publishing House. Research publishes fundamental research in the life and physical sciences as well as important findings or issues in engineering and applied science. The journal publishes original research articles, reviews, perspectives, and editorials. IF=10.7，Citescore=13.3.
Sources: https://spj.science.org/doi/10.34133/research.0909
Journal
Research
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
High-Efficiency and High-Capacity Aqueous Electrochromic Energy Storage Devices Enabled by Decoupled Titanium Oxide/Viologen Derivative Hybrid Materials
Article Publication Date
3-Oct-2025