Search

Elucidating the correlation between coordination structures and catalytic performances of single-atom active sites is imperative for the precise design of highly efficient catalysts; however, the feasible regulation of coordination environments in single-atom catalysts presents a formidable challenge. Herein, we fabricate single-atom Ru-based catalysts with Ru–F4 and Ru–O4 configurations (named Ru–F4 SAs/PA and Ru–O4 SAs/PA, respectively), demonstrating that fine-tuning of the coordination structure of Ru sites can significantly enhance performances for CO2 hydrogenation to methane under mild conditions in a photo-thermal synergistic catalytic process. Comparative studies reveal that Ru–F4 SAs/PA outperformed Ru–O4 SAs/PA counterparts, giving superior CO2 methanation performances with a CH4 production rate of 47.4 mmol gcat−1 h−1 and CH4 selectivity of 93.8% at 200 °C in the presence of light irradiation (200–1100 nm, 1.9 W cm−2) under atmospheric pressure. Theoretical investigations unravel that the transition from Ru–O4 to Ru–F4 coordination environments optimizes the electronic states, thereby enhancing the adsorption of reactants and intermediates. Moreover, the optimized electronic structure promotes the production and transformation of key intermediate species, lowers the energy barrier for CO2 conversion, and thus elevates the catalytic activity. This comprehensive study not only clarifies the relationship between the coordination structures of active sites and catalytic performance at the atomic-level but also offers a novel paradigm for the design of efficient CO2 conversion catalysts. [ABSTRACT FROM AUTHOR]

The n-type semiconductor SnO2 with a wide band gap (3.6 eV) is massively used in gas-sensitive materials, but pure SnO2 still suffers from a high operating temperature, low response, and tardy responding speed. To solve these problems, we prepared small-sized pure SnO2 using hydrothermal and freeze-drying methods (SnO2-FD) and compared it with SnO2 prepared using a normal drying method (SnO2-AD). The sensor of SnO2-FD had an ultra-high sensitivity to NO2 at 100 °C with excellent selectivity and humidity stability. The outstanding gas sensing properties are attributed to the modulation of energy band structure and the increased carrier concentration, making it more accessible for electron exchange with NO2. The excellent gas sensing properties of SnO2-FD indicate its tremendous potential as a NO2 sensor. [ABSTRACT FROM AUTHOR]

Aero-space aluminum alloys, as vital materials in aerospace engineering, find extensive application in various aerospace components. However, prolonged usage often leads to the emergence of fatigue natural cracks, posing significant safety risks. Therefore, research on accurate quantitative detection techniques for the cracks in aerospace-aluminum alloys is of vital importance. Firstly, based on the three-points bending experimental model, this paper prepared the fatigue natural crack specimen, and the depth of the natural crack is calibrated. Then, given the complexity of geometric characteristics inherent in natural cracks, the pulsed eddy current signal under the different natural crack depth is acquired and analyzed using an experimental study. Finally, to better exhibit the non-linearity between PEC signal and crack depth, a GA-based BPNN algorithm is proposed. The Latin Hypercube method is considered to optimize the population distribution in the genetic algorithm. The results indicate that the characterization accuracy reaches 2.19% for the natural crack. [ABSTRACT FROM AUTHOR]

This research focuses on the under-studied phenomenon of maritime borders by providing a civilian perspective on how fishers live, negotiate, contest, and transcend state borders and surveillance at sea. It explores the everyday transboundary practices of Chinese fishers in the geopolitically sensitive South China Sea (SCS), examining their cross-border tactics to sustain fishing livelihoods and the mechanisms underpinning these tactics. Based on long-term, continuous ethnographic investigations, we unravel four tactics employed by Chinese fishers to elude the constraints of territorial borders: contract production, trans-territorial production, paying for the sea, and the appropriation of marine physicality. These transboundary strategies are supported by three mechanisms, including common fisher identity, historical transnational networks, and regional development structures. This research shows the agency and creativity of fishers in challenging and punctuating maritime territoriality in the context of increasing militarisation and securitisation of borderlands. It illustrates how the distinct materiality, mobility, and temporality of the ocean can be weaponised by fishers to undermine state-bordering processes. By exposing the extensive, dynamic, and complex civilian interactions and collaborations in the region, we demonstrate that the SCS is more than a geopolitical space but at the same time a social site of cooperation and solidarity. In doing so, this research contributes to studies of maritime borders and civilian geopolitical subjectivity by illuminating the flexibility of fishers in exercising powers on borders at sea. It also advances the existing SCS area studies by 'peopling' the political geography of the region. [ABSTRACT FROM AUTHOR]