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Single Nickel Atoms Anchored on Nitrogen-Doped Graphene as a Highly Active Co-Catalyst for Photocatalytic H2 Evolution
摘要： Earth abundant nickel is a typical non-noble-metal cocatalyst used for photocatalytic hydrogen evolution (PHE). Ni nanoparticles, however, tend to aggregate during the hydrogen production process, significantly lowering their PHE activity. In this research, we report single nickel atoms anchored on nitrogen-doped graphene (Ni-NG) as a cocatalyst for PHE. We have demonstrated that Ni-NG is a robust and highly active cocatalyst for PHE from water. With only 0.0013 wt.% of Ni loading, the PHE activity of composite Ni-NG/CdS photocatalyst is 3.4 times greater than that of NG/CdS. The quantum efficiency of Ni-NG/CdS for PHE reaches 48.2% at 420 nm, one of the highest efficiencies for non-noble-metal based cocatalysts reported in literature. Photoluminescence spectral analyses and electrochemical examinations have indicated that Ni-NG coupled to CdS can serve not only as an electron storage medium to suppress electron-hole recombination, but also as an active catalyst for proton reduction reaction. Density functional theory calculation shows that the high activity of Ni-NG/CdS composite results from the single Ni atoms trapped in NG vacancies, which significantly reduces the activation energy barrier of the hydrogen evolution reaction. This approach may be valuable for developing robust and highly active noble-metal free cocatalysts for solar hydrogen production.
关键词： Non-noble Metal Cocatalyst,CdS,Photocatalytic Hydrogen Evolution,Nitrogen-Doped Graphene,Single Ni Atom Catalysts
更新于2025-09-23 15:21:21
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Optical wonderlands: vision science from photons to philosophy
摘要： The many eyes of scallops use reflecting mirrors, something like telescopes. Mantis shrimp have 12 classes of colour receptor to our 3. These findings in vision science are just two of many milestones in neurobiologist Michael Land’s meander through topics in the field — from the optical physics of eye function to the neurobiology of how brains interpret optical phenomena. Eyes to See is the journey of a scientist who followed his nose (and eyes) towards what fascinated him.
关键词： vision science,neurobiology,eye function,evolution of eyes,optical physics
更新于2025-09-23 15:21:21
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Phase field modeling of grain boundary migration and preferential grain growth driven by electric current stressing
摘要： A phase field model incorporating the electrostatic free energy and the grain orientation effect is developed and employed to study the grain boundary migration and preferential grain growth in widely used beta-tin (β-Sn) under electric current stressing. The directional migration of grain boundaries and the preferential growth of the grain with its orientation having low electrical resistivity along the electric current direction are theoretically clarified. In a bicrystal system containing a circular grain, the shrinkage velocity and morphology changes of grains are dominated by the competition effect between the grain boundary energy and the electrostatic free energy; in particular, the high-density electric current can induce the instability of grain morphology evolution. Moreover, grain morphology evolution leads to the change of the voltage across the β-Sn system; it is found that the voltage decreases over time in a tricrystal system, while the variation of the voltage across the bicrystal system is related to the above-mentioned competition effect. The proposed model and results provide insights into the orientation-related microstructure evolution under electric current stressing.
关键词： preferential grain growth,electric current stressing,microstructure evolution,grain boundary migration,beta-tin,phase field model
更新于2025-09-23 15:21:21
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Monolayer Attachment of Metallic MoS <sub/>2</sub> on Restacked Titania Nanosheets for Efficient Photocatalytic Hydrogen Generation
摘要： Monolayer attachment of metallic MoS2 (1T) on restacked titania (Ti0.87O2 0.52?) nanosheets was attained via a facile two-step flocculation process of their colloidal suspensions with the aid of the difference in critical H+ concentrations required for inducing flocculation of the respective nanosheets. The process produced porous flaky aggregates of restacked Ti0.87O2 0.52? nanosheets covered with monolayer MoS2, which serves as the electron collector and provides abundant catalytically active sites for proton reduction reaction. The MoS2-modified restacked-Ti0.87O2 0.52? nanosheets showed a remarkably high photocatalytic efficiency for hydrogen generation (1.2 mmol h-1 g-1), being superior to those of the restacked Ti0.87O2 0.52? nanosheets and P25-TiO2 nanoparticles conventionally modified with MoS2 (0.38, and 0.4 mmol h-1 g-1, respectively). The extensive molecular-level interfacial coupling of Ti0.87O2 0.52?/MoS2 nanosheets facilitates efficient charge separation and fast electron transfer, resulting in the significantly enhanced photocatalytic activity.
关键词： 2D heterointerface,photocatalysis,hydrogen evolution,two-step flocculation process,monolayer co-catalyst
更新于2025-09-23 15:21:21
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OPTIMAL DESIGN OF A KU/KA-BAND WIDE-FLARE-ANGLE CORRUGATED HORN USING THE DIFFERENTIAL EVOLUTION ALGORITHM
摘要： A novel wide-flare-angle corrugated horn covering the full Ku/Ka satellite communication frequency bands is designed and optimized. In order to satisfy the rigorous bandwidth requirements, a spline-profiled smooth section and a corrugated section with ring-loaded slots are introduced into the wide-flare-angle horn design. Instead of the “trial-and-error” method, the Differential Evolution (DE) algorithm is employed to obtain the optimum dimensions of the proposed horn. A prototype of the optimized horn is constructed and measured. Both simulated and measured results show that the proposed horn has good radiation and impedance performance. The performance of the horn is also demonstrated as a feed in a typical dual-reflector antenna. Simulation results show that the overall antenna system meets the usual performance requirements.
关键词： Ku/Ka-band,satellite communication,wide-flare-angle corrugated horn,Differential Evolution algorithm
更新于2025-09-23 15:21:21
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Sulfur-doped porous graphitic carbon nitride heterojunction hybrids for enhanced photocatalytic H2 evolution
摘要： Graphitic carbon nitride (g-C3N4) is considered as an attractive, efficient and newly generated photocatalyst material owing to its distinct properties such as metal free, suitable band gap and high physicochemical stability. Nevertheless, the photocatalytic activity of pure g-C3N4 was limited by the fast recombination rate of photoinduced electron–hole pairs and relatively low specific surface area. In this study, we provide a new prospect to overcome the problem by using another suitable precursor urea-assisted copolymerization with thiourea which is expected to optimize the process of thermal condensation, inhibit agglomeration and improve the specific surface area; meanwhile, the formed isotype heterogeneous junction effectively inhibits charge carrier recombination. The formed g-C3N4 isotype heterojunction photocatalyst manifested significant improvement photocatalytic hydrogen production than the single and pure g-C3N4 sample. This significant enhanced photocatalytic performance is mainly ascribed to inhibited recombination, enriched active site and enlarged specific surface area.
关键词： porous graphitic carbon nitride,heterojunction hybrids,photocatalytic H2 evolution,Sulfur-doped
更新于2025-09-23 15:21:21
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Fabrication of Robust Nanostructured (Zr)BiVO4/Nickel Hexacyanoferrate Core/Shell Photoanodes for Solar Water Splitting
摘要： A highly conformal 10-15 nm layer of NiFe based Prussian blue co-catalyst is coated on BiVO4 electrodes. The coating boosted the photocurrent of BiVO4 electrodes by 10-fold to 3.23 mA/cm2. A low onset potential of 0.2 V and photo-corrosion inhibition for > 50 hours are also achieved.
关键词： Prussian blue,bismuth vanadate,solar water splitting,oxygen evolution catalyst
更新于2025-09-23 15:21:21
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Bimetallic PtNi/g-C3N4 nanotubes with enhanced photocatalytic activity for H2 evolution under visible light irradiation
摘要： Bimetallic PtNi-decorated graphitic carbon nitride (g-C3N4) nanotubes were prepared through calcining the mixture of urea and thiourea in the presence of Pluronic F127, followed by deposition of bimetallic PtNi nanoparticles (NPs) via chemical reduction. It is found that the photocatalytic activity of PtNi/g-C3N4 nanotubes is strongly dependent on the molar ratio of Pt/Ni and the highest activity is observed for Pt1Ni1/g-C3N4. Under visible light (l > 420 nm) irradiation, the H2 generation rate over Pt1Ni1/g-C3N4 nanotubes is 104.7 mmol h?1 from a triethanolamine (10 vol%) aqueous solution, which is higher than that of Pt/g-C3N4 nanotubes (98.6 mmol h?1) and is about 47.6 times higher than that of pure g-C3N4 nanotubes. The cyclic photocatalytic reaction indicates that our Pt1Ni1/g-C3N4 nanotubes function as a stable photocatalyst for visible light-driven H2 production. The effect of bimetallic PtNi NPs in the transfer and separation of photogenerated charge carriers occurring in the excited g-C3N4 nanotubes was investigated by performing photoelectrochemical and photoluminescence measurements. Our results reveal that bimetallic PtNi could replace Pt as a promising cocatalyst for photocatalytic H2 evolution with better performance and lower cost.
关键词： Hydrogen evolution,g-C3N4,Nanotube,Bimetallic PtNi,Photocatalyst
更新于2025-09-23 15:21:21
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Simultaneously engineering K-doping and exfoliation into graphitic carbon nitride (g-C3N4) for enhanced photocatalytic hydrogen production
摘要： Doping and exfoliation are effective strategies to improve the photocatalytic activity of bulk graphitic carbon nitride (g-C3N4). Therefore, it can be inferred that engineering element-doping and exfoliation into g-C3N4 would further enhance the photocatalytic performance. Herein, we demonstrated a KOH-assisted hydrothermal-reformed melamine strategy for achieving the simultaneous K-doping and exfoliation of g-C3N4. The as-synthesized K-doped g-C3N4 ultrathin nanosheets displayed much enhanced photocatalytic hydrogen evolution rate (HER) of about 13.1 times higher than that of the bulk g-C3N4 under visible-light irradiation, achieving an apparent quantum efficiency of 6.98% at 420 nm. The improved photocatalytic HER can be attributed to the high surface area offering numerous photocatalytic active sites, enlarged conductive band edge optimizing photoreduction potential, and K-doping promoting charge generation and separation as well as the long life-time of photogenerated carriers. This work would provide a promising way to integrate co-doping and exfoliation into new g-C3N4-based materials.
关键词： Graphitic carbon nitride,Exfoliation,Photocatalytic hydrogen evolution,Nanosheet,K-doping
更新于2025-09-23 15:21:21
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Medium-resolution Optical and Near-infrared Spectral Atlas of 16 2MASS-selected NIR-red Active Galactic Nuclei at <i>z</i> ～ 0.3
摘要： We present medium-resolution spectra (R～2000–4000) at 0.4–1.0 μm and 0.7–2.5 μm of 16 active galactic nuclei (AGNs) selected with red color in the near-infrared (NIR) of J?K>2.0 mag at z～0.3. We fit the Hβ, Hα, Pβ, and Pα lines from these spectra to obtain their luminosities and line widths. We derive the E(B?V) color excess values of the NIR-red AGNs using two methods, one based on the line-luminosity ratios and another based on the continuum slopes. The two E(B?V) values agree with each other at rms dispersion ～0.249. About half of the NIR-red AGNs have g′?K<5 magnitude, and we find that these NIR-red, but blue in optical-NIR AGNs, have E(B?V)～0, suggesting that a significant fraction of the NIR color-selected red AGNs are unobscured or only mildly obscured. After correcting for the dust extinction, we estimate the black hole (BH) masses and the bolometric luminosities of the NIR-red AGNs using the Paschen lines to calculate their Eddington ratios (λEdd). The median Eddington ratios of nine NIR-red AGNs (log(λEdd)=?0.654±0.176) are only mildly higher than those of unobscured type 1 AGNs (log(λEdd)=?0.961±0.008). Moreover, we find that the MBH–σ* relation for three NIR-red AGNs is consistent with that of unobscured type 1 AGNs at similar redshift. These results suggest that the NIR-red color selection alone is not effective at picking up dusty, intermediate-stage AGNs.
关键词： quasars: general,quasars: emission lines,galaxies: Seyfert,quasars: supermassive black holes,galaxies: active,galaxies: evolution
更新于2025-09-23 15:21:21