#South Korea #Seoul #Thermal Management #SEOULTECH #Sodium Electrochromic

SEOULTECH Researchers Break Ground in Electrochromic Technology

In a significant advancement for energy-efficient building technologies, researchers at Seoul National University of Science and Technology (SEOULTECH) have developed a new type of sodium-based electrochromic window that promises to redefine thermal management. Electrochromic materials have the ability to change their color or opacity when a small voltage is applied, leading to dynamic control of sunlight and heat entering a building. The innovation centers around hexagonal tungsten oxide nanorods, which effectively block near-infrared (NIR) sunlight — the primary contributor to heat gain.

Thermal management is increasingly vital in the face of rising energy costs and climate change. It aims to minimize the energy needed for heating and cooling residential and commercial buildings. The researchers recognized that while lithium-based electrochromic materials have offered some solutions, their dependence on lithium, a costly and less abundant resource, posed limitations. In contrast, sodium is more readily available and economically beneficial. However, sodium ions previously faced challenges in accessing the tunnels of the nanorods due to steric hindrance from the dopants needed for structural integrity.

The innovative approach taken by the SEOULTECH team was to introduce thermally removable dopants, which can be eliminated via simple heat treatment. This breakthrough allows sodium ions to effectively occupy the hexagonal tunnels within the tungsten oxide, leading to efficient NIR modulation. Dr. Sungyeon Heo, an assistant professor involved in the project, stated, “Our strategy allows effective utilization of the hexagonal tunnels for sodium-ion insertion. Consequently, we demonstrate that low-cost sodium electrolytes can achieve large NIR modulation, comparable to that of lithium-based system.”

With a film thickness of only 150 nm, the developers believe that their materials can perform equally well as lithium-based alternatives in blocking heat. The nanomaterials are produced in a single reaction batch, enabling straightforward scaling up for potential large-scale applications. The colloidal form of these nanomaterials further broadens their usability — they can be processed into various coatings or composite systems, making them versatile for use in numerous applications beyond electrochromism.

The implications of this technology are promising, particularly in regions with extreme temperatures, such as parts of Africa and the Middle East. Electrochromic windows could maintain continuous heat-blocking states, significantly reducing reliance on air conditioning and promoting energy savings. Conversely, in areas with varying seasons, the optical properties of these windows can adapt according to user preferences and climatic demands, optimizing both heating and cooling efficiencies throughout the year.

As we look to the future, the SEOULTECH team's innovation could pave the way for smarter buildings and windows — automatically adjusting to ambient light and heat levels. This could see energy savings and greatly enhance indoor comfort levels. Dr. Heo emphasizes that their research focuses on sustainability, stating, "Our study demonstrates material designs and processing strategies that are compatible with low-cost Earth-abundant components, such as sodium electrolyte, and scalable synthesis methods."

This research, published in the journal Nano Letters, represents a key step toward fostering sustainability in everyday life and reducing our overall energy demand. The world stands on the brink of a new energy-efficient era in building materials, thanks to this promising development from SEOULTECH.

Reference

Title of original paper: Unlocking Na+-Based Electrochromic Capacity in Hexagonal Tungsten Oxide Nanorods via Thermally Removable Dopants
Journal: Nano Letters
DOI: 10.1021/acs.nanolett.5c04697

For more information, visit SEOULTECH's website.