As global freshwater scarcity intensifies, solar-driven interfacial evaporation has emerged as a promising sustainable solution for seawater desalination and wastewater purification. However, conventional solar-thermal evaporators face a critical bottleneck: they excel at water evaporation yet fail to address complex organic pollutants, while catalytic degradation systems operate independently without leveraging solar energy. Now, researchers led by Professor Xiang Feng, Professor Jiao Qu, and their team have presented a breakthrough multifunctional nanocage architecture that seamlessly integrates ultrafast solar evaporation with selective pollutant degradation in a single material.
Why This Nanocage Matters
Traditional dual-function systems merely coat catalysts onto porous evaporation substrates, causing structural complexity and inevitable performance conflicts. The novel nitrogen-coordinated single-atom Fe-doped mesoporous carbon nanocages encapsulating plasmonic Au nanoparticles (FCC@Au) overcome this limitation by intrinsically coupling nano-confined solar-thermal evaporation with non-radical advanced oxidation catalysis. This hierarchical design transforms a passive evaporation surface into an active, self-regulating water purification system.
Innovative Design and Mechanism
The material is synthesized through a polymer coating–pyrolysis–etching strategy, creating hollow carbon nanocages (~200 nm) with Au nanoparticles embedded on inner walls and atomically dispersed Fe–N 4 sites integrated into the carbon shells. The architecture operates through a synergistic triple mechanism: (i) broadband solar light harvesting via the carbon framework and Au LSPR effect; (ii) nano-confinement-induced generation of intermediate water with weakened hydrogen bonding, lowering vaporization enthalpy from 2451 kJ kg -1 (pure water) to 1105 kJ kg -1 ; and (iii) localized physical field modulation from interior Au nanoparticles that establishes directional thermal and pressure gradients, accelerating water transport through mesoporous channels.
Molecular dynamics simulations reveal that within the nano-confined pores, the average hydrogen bond number per water molecule decreases radially from 1.7 to 1.0 as molecules approach the pore wall, confirming the transition from bound water to easily evaporated intermediate water. In situ Raman spectroscopy further validates this: the intermediate-to-free water ratio increases dramatically from 0.332 in bulk water to 1.117 in the FCC@Au system under illumination.
Outstanding Evaporation Performance
FCC@Au delivers a record-breaking water evaporation rate of 2.56 kg m -2 h -1 in 2D planar configuration under 1-sun irradiation—among the highest reported for planar solar-thermal evaporators. When integrated into a 3D polyurethane foam architecture, the evaporation rate surges to 6.84 kg m -2 h -1 , significantly outperforming benchmark carbon nanotube systems (5.99 kg m -2 h -1 ). The evaporation coefficient reaches 2.74 × 10 -4 , distinctly higher than Au-free counterparts, confirming kinetic enhancement through physical field modulation. Notably, the 3D evaporator maintains stable performance exceeding 6.8 kg m -2 h -1 over 12 hours of continuous operation.
Selective Catalytic Degradation
Beyond evaporation, the Fe–N 4 sites act as highly accessible catalytic centers that activate peroxymonosulfate (PMS) via a non-radical electron transfer pathway (ETP). Unlike conventional radical-based advanced oxidation processes that indiscriminately attack all organics, this ETP mechanism achieves complete degradation of 10 ppm bisphenol A (BPA) in under 2 minutes with a mass-normalized rate constant of 182.5 L g -1 min -1 —nearly two orders of magnitude higher than most reported catalysts. Radical quenching experiments, in situ Raman spectroscopy, and H-cell electrochemical measurements collectively confirm the ETP mechanism: electrons transfer directly from BPA → Fe–N 4 → PMS*, bypassing reactive oxygen species entirely. This confers exceptional environmental adaptability—the catalyst retains high performance across broad pH ranges and in the presence of inorganic ions (Cl⁻, HCO 3 ⁻, SO 4 2- ) that typically poison radical pathways.
Applications and Future Outlook
When deployed in an outdoor solar collection device (440 cm 2 effective area) under natural sunlight in Beijing, the FCC@Au evaporator collected 550 mL of purified water over 8 hours at an average rate of 1.56 kg m -2 h -1 . The condensate meets WHO drinking water standards with >99.85% ion removal efficiency. Simultaneously, catalytic treatment of BPA-contaminated seawater eliminates pollutant fluorescence signals within 15 minutes. Seed germination tests confirm biological safety: both condensate and catalytically treated water achieve >95% germination rates, while raw seawater and BPA solution cause complete growth inhibition.
This work establishes a new paradigm for multifunctional solar-thermal materials by demonstrating that nano-confinement and localized physical fields can simultaneously regulate interfacial water structure for enhanced evaporation and mediate selective electron transfer for pollutant degradation. The strategy is readily extendable to other single-atom catalysts and 3D architectures, opening promising avenues for next-generation solar-driven water purification systems that combine high efficiency, self-cleaning capability, and environmental robustness.
Stay tuned for more groundbreaking research from this collaborative team!
Nano-Micro Letters
News article
Nano‑Confined Solar‑Thermal Water Purification Boosted by Physical Field Disturbance Coupled with Ultrafast Non‑Radical Advanced Oxidation Process
6-Jul-2026