A new study reveals how combining biochar with advanced hydrogels can dramatically improve solar-driven water evaporation, offering a promising pathway for low-energy desalination and water purification technologies.
Freshwater scarcity is a growing global challenge, with most of Earth’s water locked in oceans or saline sources. Traditional desalination methods often require high energy input and infrastructure costs. Solar interfacial evaporation, which uses sunlight to convert water into vapor at the surface, has emerged as a cleaner and more energy-efficient alternative. However, improving its efficiency remains a key scientific challenge.
In a recent study published in Biochar , researchers developed a hybrid material that integrates biochar into a polyzwitterionic hydrogel, achieving a remarkable evaporation rate of 3.57 kilograms per square meter per hour under standard sunlight conditions. This performance is significantly higher than that of conventional hydrogels and highlights the potential of biochar-based materials in sustainable water treatment.
“By introducing biochar into the hydrogel network, we were able to simultaneously enhance light absorption, water transport, and energy efficiency,” said the study’s corresponding author. “This multi-functional synergy is key to achieving high-performance solar evaporation.”
The innovation lies in how biochar interacts with the hydrogel at both physical and molecular levels. Biochar, a carbon-rich material derived from biomass such as agricultural waste, is known for its porous structure and strong light-absorbing properties. When incorporated into the hydrogel, it transforms the material from transparent to dark, enabling it to capture more sunlight across a wide spectrum. According to experimental results, the hybrid hydrogel maintained over 95 percent light absorption across a broad wavelength range.
At the same time, the addition of biochar alters the internal structure of the hydrogel. Microscopic observations, shown in figures on page 4 of the paper, reveal a denser and more interconnected pore network. This structure improves the movement of water within the material, ensuring a continuous supply of water to the evaporation surface while minimizing heat loss to the bulk liquid.
Beyond photothermal effects, the study also uncovers a less explored mechanism involving water molecule behavior. The surface functional groups of biochar interact with the hydrogen bonding network inside the hydrogel, increasing the proportion of so-called intermediate water. This form of water requires less energy to evaporate compared to tightly bound water. As a result, the hybrid material significantly reduces the energy needed for evaporation, lowering the equivalent evaporation enthalpy to 877.79 joules per gram.
This dual enhancement, combining photothermal efficiency with molecular-level water activation, enables the hybrid hydrogel to outperform many existing materials. The system also demonstrates strong water transport capabilities even in saline conditions, making it particularly suitable for seawater desalination applications.
The researchers emphasize that biochar is not only effective but also sustainable and cost-efficient, as it can be produced from agricultural residues such as sorghum straw. This adds an important environmental advantage, aligning the technology with circular economy principles.
“Our findings provide new insights into how material design can address multiple bottlenecks in solar evaporation systems,” the authors noted. “This could guide the development of next-generation evaporators for clean water production in resource-limited settings.”
As global demand for freshwater continues to rise, innovations like biochar-enhanced hydrogels could play a critical role in delivering scalable, low-carbon water treatment solutions.
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Journal Reference: Wang, S., Yang, J., Wang, A. et al. Heat loss and water transport capacity regulation in hybrid evaporators. Biochar 8 , 97 (2026).
https://doi.org/10.1007/s42773-026-00604-0
About Biochar
Biochar (e-ISSN: 2524-7867) is the first journal dedicated exclusively to biochar research, spanning agronomy, environmental science, and materials science. It publishes original studies on biochar production, processing, and applications—such as bioenergy, environmental remediation, soil enhancement, climate mitigation, water treatment, and sustainability analysis. The journal serves as an innovative and professional platform for global researchers to share advances in this rapidly expanding field.
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Biochar
Experimental study
Heat loss and water transport capacity regulation in hybrid evaporators
27-Apr-2026