Shanyuan Niu

Developing photo-Fenton catalysts that efficiently couple photogenerated charge separation with Fe redox cycling is essential for improving water treatment. Here, a TiO₂-500/FeOCl_fev heterojunction was constructed to combine interfacial charge transfer with H₂O₂-assisted oxidation. The optimized 1:1 composite removed approximately 90% of sulfamethoxazole (SMX) within 10 min under simulated solar irradiation, whereas TiO₂-500 and FeOCl achieved only 12.7% and 13.2% removal, respectively, under otherwise identical conditions; the NaCl-assisted FeOCl_fev-0.15 component achieved 81.9% removal. Structural and spectroscopic analyses indicate intimate interfacial contact, extended visible-light absorption, and interfacial electronic interactions. Enhanced photocurrent and a reduced electrochemical impedance arc further suggest more efficient charge separation and transport. Scavenger and electron spin resonance experiments identify •O₂⁻ and h⁺ as the dominant reactive species, with •OH also contributing. A possible direct Z-scheme pathway and Fe-mediated H₂O₂ activation are proposed to explain the observed behavior. These results demonstrate that coupling TiO₂-500 with NaCl-assisted FeOCl is a promising strategy for improving photo-Fenton catalysis for antibiotic abatement.

Quinone‐based metal‐free electrocatalysts offer a sustainable route for oxygen activation and water purification, yet their persistent activity decay has remained poorly understood. Here, we identify mineralization‐derived CO ₂ as the major cause of a previously overlooked self‐poisoning pathway in quinone‑based electrocatalysts: CO ₂ accumulates at the electrode–electrolyte interface and forms stable carbonate adducts with reduced quinone moieties, blocking the active sites for two‐electron oxygen reduction to H ₂ O ₂ and consequently suppressing ·OH generation through the cascade oxygen‐reduction pathway. Electrochemical analysis further reveals that CO ₂ adduction reorganizes the native quinone redox transitions into potential‐dependent carbonate‐bound states, allowing the occupied quinone centers to be reversibly regenerated by oxidative pulses. Leveraging this principle, we developed a pulsed electrocatalytic strategy that periodically reoxidizes the quinone catalyst in situ, dynamically reversing CO ₂ poisoning without requiring chemical regenerants or thermal treatment. Across structurally diverse pollutants at neutral pH, this strategy accelerates degradation kinetics by up to 725.3% and retains up to 93.6% of its 2 h diclofenac removal efficiency after 12 h of continuous operation. More broadly, the redox‐gated CO ₂ switching mechanism provides a generalizable design paradigm for mitigating CO ₂ ‐induced deactivation in electrocatalytic systems prone to local CO ₂ buildup, including CO ₂ electrolysis, electrosynthetic biomass conversion, and electrochemical nitrogen fixation.

Quinone‐based metal‐free electrocatalysts offer a sustainable route for oxygen activation and water purification, yet their persistent activity decay has remained poorly understood. Here, we identify mineralization‐derived CO ₂ as the major cause of a previously overlooked self‐poisoning pathway in quinone‑based electrocatalysts: CO ₂ accumulates at the electrode–electrolyte interface and forms stable carbonate adducts with reduced quinone moieties, blocking the active sites for two‐electron oxygen reduction to H ₂ O ₂ and consequently suppressing ·OH generation through the cascade oxygen‐reduction pathway. Electrochemical analysis further reveals that CO ₂ adduction reorganizes the native quinone redox transitions into potential‐dependent carbonate‐bound states, allowing the occupied quinone centers to be reversibly regenerated by oxidative pulses. Leveraging this principle, we developed a pulsed electrocatalytic strategy that periodically reoxidizes the quinone catalyst in situ, dynamically reversing CO ₂ poisoning without requiring chemical regenerants or thermal treatment. Across structurally diverse pollutants at neutral pH, this strategy accelerates degradation kinetics by up to 725.3% and retains up to 93.6% of its 2 h diclofenac removal efficiency after 12 h of continuous operation. More broadly, the redox‐gated CO ₂ switching mechanism provides a generalizable design paradigm for mitigating CO ₂ ‐induced deactivation in electrocatalytic systems prone to local CO ₂ buildup, including CO ₂ electrolysis, electrosynthetic biomass conversion, and electrochemical nitrogen fixation.

Efficient photo-Fenton catalysis requires the simultaneous optimization of light harvesting, photogenerated-charge utilization, and metal-mediated H₂O₂ activation. Herein, amorphous Cu-FeOOH clusters were assembled on oxygen-vacancy-rich Fe-doped BiOCl nanoflowers (Fe-BOCov) to construct a Cu-FeOOH/Fe-BOCov composite for efficient photo-Fenton catalysis. Oxygen-vacancy engineering and Cu-FeOOH coupling extended visible-light absorption and improved interfacial charge separation, as supported by the enhanced photocurrent response and reduced electrochemical impedance. Under AM 1.5G simulated solar irradiation, the optimized catalyst removed more than 90% of levofloxacin (LEV) within 10 min and exhibited an apparent pseudo-first-order rate constant of 0.271 min⁻¹. Radical-quenching and electron spin resonance measurements identify •OH and •O₂⁻ as the principal reactive species, with photogenerated holes also contributing. A mechanism is proposed in which electrons generated in oxygen-vacancy BiOCl migrate to Cu-FeOOH sites, facilitate Fe(III)/Fe(II) and Cu(II)/Cu(I) cycling, and accelerate H₂O₂ activation. This work demonstrates a defect-and-interface strategy for coupling solar-energy utilization with bimetallic Fenton chemistry.

Furfural is a pivotal indicator of the aging condition of transformer oil-paper insulation. Traditional analytical techniques such as liquid chromatography require sophisticated pretreatment and phase-separation procedures and are therefore not well suited to rapid oil-sample analysis. This study reports the direct analysis of furfural in complex oil mixtures using surface-enhanced Raman spectroscopy (SERS). The weak vibrational response of furfural in oil was enhanced using a Au-coated silicon nanowire substrate fabricated by metal-assisted chemical etching (MACE). The textured metal-coated surface enabled trace furfural at the μL/L level to be measured directly in the oil mixture without adsorption enrichment or chemical extraction, with the entire test process completed within 1 min. Peak deconvolution was used to extract the fitted area of the 1365 cm⁻¹ band, and the relationship between this Raman response and furfural concentration yielded R² = 0.9910. Temperature- and pressure-dependent measurements were also performed to examine their effects on the positions of the main Raman peaks. This work demonstrates a rapid approach for analyzing trace furfural in complex liquid mixtures and provides a basis for further spectroscopic studies of transformer oil-paper insulation aging.

Methanol is a critical molecular marker for the early aging of oil-paper insulation, and its rapid detection is highly valuable for insulation condition assessment and the fault warning of power transformers. Widely used chromatographic methods require sophisticated pretreatment workflow and are not suitable for in situ monitoring. Non-destructive spectroscopic methods remain challenging due to the intrinsically small cross section of trace molecules in complex liquid environments. The rapid, direct detection of trace methanol in an oil mixture has yet to be demonstrated. In this study, a high-performance Raman-enhancing substrate was developed through hierarchical microstructure regulation, combining microscale light-trapping structures and nanoscale field-confinement sites to sense the weak Raman response of methanol in transformer oil. Direct detection of ppm-level methanol in the oil matrix was achieved, without additional adsorption enrichment or other complicated pretreatment procedures. The characteristic Raman band of methanol in transformer oil was identified, and a quantitative sensing method was established. Furthermore, the intrinsic temperature-dependent Raman response of methanol was investigated to evaluate the stability of its characteristic fingerprint bands over a broad temperature range. This work demonstrates a rapid, sensitive, and pretreatment-free spectroscopic strategy for trace methanol detection in complex oil matrices, and also sheds light on the high-sensitivity detection of small molecular markers in complex liquid environments.

Polar skyrmion nanodomains in ferroelectric materials, analogous to those in ferromagnetic systems, have attracted significant attention because of the polar states and their potential application in memories. Complex higher order topological structures such as skyrmionium and skyrmion bags found in magnetic systems possess better stability and tunability, though their counterparts are yet to be realized in ferroelectric systems. Herein, we report the observation of intricate ferroelectric domain structures in epitaxial Pb(Zr0.1Ti0.9)O3 thin films that resemble skyrmioniums with concentric skyrmions of opposing charges and skyrmion bags with additional degrees of freedom via inner skyrmions. These nanodomains result from relaxation and correlated atomic displacement in thin films and can be tuned by substrate-induced strain. Reversible transitions between three distinct topological charge states, including skyrmion (Q = 1), skyrmionium (Q = 0), and skyrmion bags (Q = 2, 4), can be controlled by external bias at room temperature. In addition, switching of topological charge states facilitates highly conducting channels with more than three orders of magnitude higher current flow than the ferroelectric matrix. Such conducting channels can also be readily configured to arbitrary patterns via scanning a biased tip. Overall, these high-density polar topological structures with superior tunability and room-temperature stability offer prospects for programmable ferroelectric devices.

Paper has been one of the most widely used sustainable materials for millennia. It is fascinating that its two-dimensional (2D) microstructure consisting of randomly stacked plant fibers has not significantly changed. Such laminate structure leads to paper’s limited mechanical strength and vulnerability to water. Here, we report a novel Metapaper architecture with unprecedented mechanical properties and a scalable roll-to-roll manufacturing process. The Metapaper consists of paper fibers tightly knitted with each other in three-dimensions (3D). Compared with conventional paper, Metapaper exhibits ultra-high mechanical properties, even in aqueous environments. A wet tensile strength of 11.2 MPa, fracture work of 797 KJ/m3 and abrasion resistance of 708 cycles have been achieved, which is about 16, 56 and 350 times more than that of regular paper, respectively. It can be folded over 600 times when loaded with 250g weight and bent at 135° under wet conditions, whereas regular paper would break down upon any folding operation. Except superior mechanical properties, Metapaper is completely additive-free, fully degradable and retains regular paper’s pleasurable visual and tactile sensations. We also demonstrate continuous roll-to-roll production of 3D Metapaper up to 45 cm in width with minimal add-on cost. The unprecedented mechanical properties of 3D Metapaper and its easily scalable manufacturing processes enable new prospects for paper’s applications.