Harnessing nanoscale defects in atomically thin chromiteen, researchers have built a bendable device that produces volts from ocean waves.
Study: Strain-induced wave energy harvesting using atomically thin chromiteen. Image Credit: Vallabh Soni/Shutterstock.com
Researchers have shown how atomically thin chromiteen, derived from naturally defect-rich chromite ore, can convert the gentle motion of ocean waves into electrical energy through strain-induced surface charge modulation.
Their findings, published in Nanoscale, reveal a flexible, corrosion-resistant nanogenerator designed for marine environments.
2D materials have long attracted attention for energy harvesting because of their exceptional electronic and mechanical properties. Chromiteen, a layered form of FeCr2O4, stands out for its chemical stability, high surface charge density, and ability to host naturally occurring defects that influence electron behavior.
When such materials undergo mechanical strain, they experience charge redistribution at the atomic scale, a mechanism that can generate useful electricity through flexoelectricity.
How Chromiteen was Formed
The researchers exfoliated chromite ore using liquid-phase exfoliation, producing few-layer sheets verified via SEM, AFM, XRD, FTIR, and zeta potential measurements.
These nanosheets were then encapsulated in thermoplastic polyurethane (TPU), creating a flexible composite in which the strain applied to the polymer is transferred directly to the embedded chromiteen.
This film formed the core of a nanogenerator designed to mimic the motion of water waves. Mechanical bending produced controlled strain levels up to 4.2 %, allowing the team to track how deformation affected charge generation.
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Investigating How Surface Defects Produce Energy
Raman spectroscopy revealed distinct peak shifts and splitting under strain, confirming lattice symmetry breaking, which is a key flexoelectric signature.
Zeta potential measurements indicated a negatively charged surface, while microscopy confirmed the presence of vacancies and structural irregularities introduced during exfoliation.
When tested in a wave simulator, the chromiteen-TPU device produced an open-circuit voltage of around 5 V under high-turbulence conditions.
Output increased consistently with both strain and wave intensity, reflecting the direct relationship between mechanical deformation and electrical generation.
To understand how strain and defects shape electronic behavior, the researchers used density functional theory (DFT) calculations. Models of pristine, strained, and oxygen-deficient chromiteen showed clear charge redistribution, altered bond lengths, and localized electronic states near vacancies.
These effects contribute to enhanced polarization and improved device performance under mechanical load.
Mechanical testing showed that the composite film could stretch to several times its original length before breaking, with the 2D sheets reinforcing the TPU matrix.
When submerged in saltwater for several days, the film retained its overall structural integrity, although electrical output dropped by roughly 35 % due to surface oxidation, indicating durability but not full corrosion immunity.
Conclusion
This work demonstrates how ultrathin chromiteen, supported by polymer encapsulation and inherently rich defect structures, can generate meaningful electrical output from real-world wave motion.
While long-term saltwater exposure still affects performance, the combination of flexibility, atomic-scale responsiveness, and marine compatibility positions chromiteen-based devices as promising candidates for powering distributed ocean sensors and small marine electronics.
Journal Reference
Mathias R., et al. (2025). Strain-induced wave energy harvesting using atomically thin chromiteen. Nanoscale. DOI: 10.1039/d5nr04273a