Efficient activation of molecular oxygen into reactive oxygen species is central to photocatalytic antibiotic degradation. Here, we prepared an edge-oriented CeO2 at the edges of carbon nitride (10-CeO2/CN) through a straightforward precursor adsorption followed by a hydrothermal process, where Ce is preferentially anchored at the CN edges. The 10-CeO2/CN achieves 89.2% tetracycline (TC) removal and 63.9% mineralization under visible-light irradiation, markedly outperforming pristine CN and CeO2. Experimental results and finite-element simulations demonstrate that edge-oriented CeO2 functions as an optical antenna for photon harvesting and a dielectric mirror to confine light at the interface, leading to 2.58-fold enhancements in the local optical field relative to CN and extending the photon propagation path and residence time. Density functional theory calculations further reveal that edge-oriented CeO2 exposes a highly reactive (200) facet, substantially enhancing O2 adsorption for activation. The enhanced interfacial optical field, coupled with facet-dependent O2 activation, enables the generation of singlet oxygen, thereby enabling efficient TC removal. These findings reveal the pivotal role of crystallographic orientation in coupling interfacial optical-field modulation with facet-dependent O2 activation, providing mechanistic insight into the rational design of high-performance photocatalysts for antibiotic degradation.
Ammonia (NH3) is a promising green hydrogen carrier, and its synthesis under mild, distributed conditions has attracted increasing attention. Non-thermal plasma provides a potential route for ammonia synthesis by enabling nitrogen activation through electron-driven processes. This study investigates catalyst-free NH3 synthesis in a flowing water-electrode dielectric barrier discharge (DBD) reactor driven by alternating current (AC), unipolar pulse, and bipolar pulse. Electrical diagnostics and optical emission spectroscopy were used to examine how excitation mode affects discharge behavior, energy utilization, and nitrogen activation. Nanosecond pulsed excitation improved NH3 synthesis performance compared with AC excitation under the tested conditions. Unipolar pulsing was more favorable in the low specific energy input (SEI) regime, whereas bipolar pulsing maintained better performance at higher SEI, which was associated with discharge regulation induced by periodic field reversal. Optical emission analysis indicated that bipolar excitation showed a slightly higher mean effective reduced electric field, together with stronger N2+-related emission. These results suggest enhanced electron-impact excitation and ionization characteristics and highlight the role of excitation waveform in regulating discharge behavior and energy utilization in catalyst-free plasma-assisted ammonia synthesis.
CO2 sequestration is critical for mitigating climate change, with hydrate-based CO2 sequestration technology showing significant promise for commercial application. Hydrate reservoirs with underlying gas layers, demonstrated by experimental studies and field production to have high commercial potential for natural gas production, are also promising for CO2 storage, yet their sequestration characteristics remain unexplored. In this study, the formation kinetics and morphological characteristics of CO2 hydrates were investigated experimentally, with a focus on the effects of sediment, initial water saturation, and underlying gas. The morphological compared results show that underlying gas-sediment synergy induces vein-like hydrate morphologies and preferential gas channels. Compared to sediment systems without underlying gas, the hydrate induction time (ti) is reduced by 52%, and the gas consumption per unit volume of water is increased by 156%. Compared to pure water systems, sediments shorten ti by 97% and t90 by 47%, while boosting unit water gas consumption by 376%. Initial water saturation shows a nonlinear effect on CO2 hydrate formation kinetics by affecting water supply, gas diffusion, and pore connectivity. These findings highlight the pronounced promoting effect of underlying gas on CO2 hydrate formation and confirm the strong carbon sequestration capacity of hydrate reservoirs with underlying gas layers.
Asphalt pavement is widely used in tunnels, and its ignition and combustion behaviors under fire exposure is of great safety concern. Although most existing studies have focused mainly on asphalt binders and assumed relatively fixed ignition criteria, the influence of aggregates on critical ignition conditions and combustion characteristics in different heat fluxes remains insufficiently understood. This study established a controlled laboratory platform to investigate the ignition and combustion behaviors of asphalt pavement under radiative heating representative of tunnel fire conditions. The critical heat flux, ignition time, ignition temperature, and mass loss rate were systematically quantified, the heat release characteristics and burnout depth were further evaluated. Results showed that as the external flux increased from 25 kW/m2 to 50 kW/m2, the ignition time decreased by nearly 89%, the ignition temperature dropped from 435 degrees C to 336 degrees C (-23%) with the mass loss rate increased 897%. These trends demonstrate that ignition is jointly governed by critical temperature and mass loss rate, reflecting a transition from a mass-loss-dominated regime to a temperature-dominated pyrolysis regime as heat flux increases. Combustion intensity also strengthened significantly, with the peak and total heat release rates rising by 51% and 21%, respectively, accompanied by a notably deeper burnout layer. Mechanistic analysis showed that aggregates play a decisive role in governing both ignition and burnout depth by mediating heat and mass transfer. Under low heat flux, aggregates act as a strong heat sink and promote binder migration, forming a compact barrier that delays ignition and restricts combustion to the surface. Under high heat flux, this cooling and barrier effect is overwhelmed, enabling rapid surface pyrolysis, early ignition, and deep combustion propagation. These findings provide engineering-oriented insight into heat-flux-dependent ignition mechanisms of asphalt pavement and support the development of flame-retardant pavement materials for tunnel fire safety.
Based on the phase multiplexing principle of metasurfaces and the geometric phase structure, this paper designs and verifies a multi-focal all-dielectric metalens. Alumina is selected as the material for this metalens, which is fabricated by 3D printing technology, thus featuring high transmittance and low processing cost. In the 0.1 THz band, the metalens exhibits excellent focusing performance at the designed focal points, and the experimental results are consistent with the theoretical design. By applying the phase multiplexing principle, we have successfully realized the independent regulation of the polarization state and linear polarization angle of each focal point, providing a new method for the polarization regulation of multi-focal metalens. This study not only solves the problems of high processing complexity and high cost of traditional metasurfaces but also offers new ideas and experimental basis for the practical applications of metalens in the terahertz band.
