a) Schematic illustration of
photogenerated charges and recombination processes in normal spinel oxide and
ternary spinel oxide. b) Schematic description of solar evaporation system and
c) Scalable floating device for seawater purification. Credit: Advanced Materials (2025). DOI: 10.1002/adma.202517285
A research team affiliated with
UNIST has unveiled a new technology that can convert seawater into clean
drinking water using only sunlight, without any external power source. This
breakthrough could play a crucial role in solving water shortages in developing
countries and remote island communities where electricity is often unavailable.
Led by Professor Ji-Hyun Jang from
the School of Energy and Chemical Engineering at UNIST, the team developed a
ternary oxide-based evaporator capable of efficiently using solar energy to
drive evaporation. When placed on seawater, the device heats the water, causing
it to evaporate and then condense into fresh drinking water—all without needing
electricity.
Their experiments showed that a
1-square-meter (1 m²) setup can produce about 4.1 liters of clean water in just
one hour. That is nearly seven times the natural evaporation rate of seawater,
making it the fastest oxide-based evaporator reported so far.
The study "Scalable Solar
Evaporator Based on Bandgap Engineered CuMnCrO4 Spinel Oxide with Salt-Resistant Property for Contaminated
Seawater" was published online in Advanced Materials on
December 16.
How the new material works
What makes this possible is a new
kind of photothermal material—substances that absorb sunlight and convert it into
heat. This material is coated onto the surface of the evaporator, enhancing its
ability to turn sunlight into thermal energy.
The researchers achieved this by
replacing parts of manganese in a corrosion-resistant manganese oxide with
copper and chromium, creating a new ternary oxide. By carefully adjusting the
material's composition through a process called bandgap engineering, they made
it capable of absorbing almost the entire solar spectrum—from ultraviolet to
near-infrared light—covering 97.2% of sunlight. Unlike typical oxide materials
that mainly absorb visible light, this new material captures and converts a
much broader range of sunlight into heat.
The result is a surface temperature that can reach up to 80°C, significantly higher
than previous manganese oxide-based materials, which topped out around 63°C or
74°C with copper-manganese oxides.
Innovative design prevents salt buildup
The device's design also addresses
a common challenge in solar desalination: salt buildup. It features an inverted U-shape, with a photothermal coating on the part that absorbs
water. The structure includes water-wicking fiber materials and hydrophobic
polyester fabric, which help draw water efficiently and allow salt ions to flow
away, preventing salt accumulation on the surface.
Professor Jang explained, "We have fundamentally improved the light absorption range and the photothermal efficiency of oxide materials, which allowed us to develop a high-performance, durable evaporator. Its scalability and stability mean it could be a practical solution to real-world water shortages."
Source: High-performance solar evaporator rapidly transforms seawater into fresh drinking water
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