Electrochemical nitrogen reduction reaction (NRR) over nonprecious‐metal and single‐atom catalysts has received increasing attention as a sustainable strategy to synthesize ammonia. However, the ...atomic‐scale regulation of such active sites for NRR catalysis remains challenging because of the large distance between them, which significantly weakens their cooperation. Herein, the utilization of regular surface cavities with unique microenvironment on graphitic carbon nitride as “subnano reactors” to precisely confine multiple Fe and Cu atoms for NRR electrocatalysis is reported. The synergy of Fe and Cu atoms in such confined subnano space provides significantly enhanced NRR performance, with nearly doubles ammonia yield and 54%‐increased Faradic efficiency up to 34%, comparing with the single‐metal counterparts. First principle simulation reveals this synergistic effect originates from the unique Fe–Cu coordination, which effectively modifies the N2 absorption, improves electron transfer, and offers extra redox couples for NRR. This work thus provides new strategies of manipulating catalysts active centers at the sub‐nanometer scale.
The utilization of regular surface cavities with a unique microenvironment on graphitic carbon nitride as “subnano reactors” can precisely confine multiple Fe and Cu atoms for nitrogen reduction reaction (NRR) electrocatalysis. The synergy of the Fe and Cu atoms in such confined subnano space provides significantly enhanced NRR performance, in terms of much increased ammonia yield and faradic efficiency.
Precisely regulating the electronic structures of metal active species is highly desirable for electrocatalysis. However, carbon with inert surface provide weak metal–support interaction, which is ...insufficient to modulate the electronic structures of metal nanoparticles. Herein, we propose a new method to control the electrocatalytic behavior of supported metal nanoparticles by dispersing single metal atoms on an O‐doped graphene. Ideal atomic metal species are firstly computationally screened. We then verify this concept by deposition of Ru nanoparticles onto an O‐doped graphene decorated with single metal atoms (e.g., Fe, Co, and Ni) for hydrogen evolution reaction (HER). Consistent with theoretical predictions, such hybrid catalysts show outstanding HER performance, much superior to other reported electrocatalysts such as the state‐of‐the‐art Pt/C. This work offers a new strategy for modulating the activity and stability of metal nanoparticles for electrocatalysis processes.
Carbon‐based substrates with an inert surface provide weak metal–support interactions that are insufficient to effectively modulate the electronic structures of the loaded metal nanoparticles. Here we show that atomic metal species on the carbon substrate can remotely communicate with the supported metal nanoparticles, inducing synergistic electronic coupling with the nanoparticles and enabling the control of their electrocatalytic activity.
The electrochemical nitrogen reduction reaction (NRR) is a promising energy‐efficient and low‐emission alternative to the traditional Haber–Bosch process. Usually, the competing hydrogen evolution ...reaction (HER) and the reaction barrier of ambient electrochemical NRR are significant challenges, making a simultaneous high NH3 formation rate and high Faradic efficiency (FE) difficult. To give effective NRR electrocatalysis and suppressed HER, the surface atomic structure of W18O49, which has exposed active W sites and weak binding for H2, is doped with Fe. A high NH3 formation rate of 24.7 μg h−1 mgcat−1 and a high FE of 20.0 % are achieved at an overpotential of only −0.15 V versus the reversible hydrogen electrode. Ab initio calculations reveal an intercalation‐type doping of Fe atoms in the tunnels of the W18O49 crystal structure, which increases the oxygen vacancies and exposes more W active sites, optimizes the nitrogen adsorption energy, and facilitates the electrocatalytic NRR.
More vacancies: Both high NH3 formation rate (24.7 μg h−1 mgcat−1) and Faradic efficiency (20.0 %) are achieved on Fe‐doped W18O49 nanowires@carbon fiber papers at −0.15 V (vs. reversible hydrogen electrode). Fe atoms not only efficiently increase the number of oxygen vacancies of W18O49, but optimize the nitrogen adsorption energy, and facilitate the electrocatalytic nitrogen reduction reaction (NRR).
Magnetic nanocomposites with well‐defined mesoporous structures, shapes, and tailored properties are of immense scientific and technological interest. This review article is devoted to the progress ...in the synthesis and applications of magnetic mesoporous materials. The first part briefly reviews various general methods developed for producing magnetic nanoparticles (NPs). The second presents and categorizes the synthesis of magnetic nanocomposites with mesoporous structures. These nanocomposites are broadly categorized into four types: monodisperse magnetic nanocrystals embedded in mesoporous nanospheres, microspheres encapsulating magnetic cores into perpendicularly aligned mesoporous shells, ordered mesoporous materials loaded with magnetic NPs inside the porous channels or cages, and rattle‐type magnetic nanocomposites. The third section reviews the potential applications of the magnetic nanocomposites with mesoporous structures in the areas of heath care, catalysis, and environmental separation. The final section offers a summary and future perspectives on the state‐of‐the art in this area.
Magnetic nanocompsites with mesoporous structures, defined shapes, and tailored properties are of immense scientific and technological interest. This review highlights recent advances in the synthesis and applications of the nanocomposites of magnetic nanoparticles and mesoporous materials with different morphology and structures. In addition, some perspectives on the future developments and directions of the synthesis, device fabrication, and application of such magnetic particle and mesoporous material nanocomposites are provided.
A good egg: A general and facile template strategy is presented for the fabrication of yolk–shell structures (see picture) with various types of movable cores, such as gold, SiO2, and magnetic Fe3O4. ...The vesicle template, formed of a fluorocarbon surfactant, is built up around the core.
Sphere we go: Monodisperse resorcinol formaldehyde (RF) resin polymer spheres with finely tunable particle size ranging from 200 to 1000 nm (see pictures) are prepared by an extension of the Stöber ...method. Pyrolysis of the RF spheres at 600 °C under N2 atmosphere yields uniform carbon spheres with a volume shrinkage of 19 %.
Carbon dots (CDs) have tremendous potential applications in bioimaging, biomedicine, and optoelectronics. By far, it is still difficult to produce photoluminescence (PL) tunable CDs with high quantum ...yield (QY) across the entire visible spectrum and narrow the emission peak widths of CDs close to those of typical quantum dots. In this work, a series of CDs with tunable emission from 443 to 745 nm, quantum yield within 13–54%, and narrowed full width at half maximum (FWHM) from 108 to 55 nm, are obtained by only adjusting the reaction solvents in a one‐pot solvothermal route. The distinct optical features of these CDs are based on their differences in the particle size, and the content of graphitic nitrogen and oxygen‐containing functional groups, which can be modulated by controlling the dehydration and carbonization processes during solvothermal reactions. Blue, green, yellow, red, and even pure white light emitting films (Commission Internationale de L'Eclairage (CIE)= 0.33, 0.33, QY = 39%) are prepared by dispersing one or three kinds of CDs into polyvinyl alcohol with appropriate ratios. The near‐infrared emissive CDs are excellent fluorescent probes for both in vitro and in vivo bioimaging because of their high QY in water, long‐term stability, and low cytotoxicity.
A solvent‐engineered approach to obtain photoluminescent carbon dots (CDs) with tunable emission from 443 to 745 nm, quantum yield within 13–54%, and narrowed full width at half maximum from 108 to 55 nm is reported. The resulting CDs can be potentially applied in the fabrication of full‐color light‐emitting films and in bioimaging both in vitro and in vivo.
Liu et al explores titanium dioxide (TiO2) crystals with tailored facets. They focus on the synthesis of TiO2 crystals with different facets, unusual properties of TiO2 crystals with different ...predominant facets, modification of the electronic structure and interfacial properties of faceted TiO2, and applications in the environment and energy.
Using the relations between the slow-roll parameters and the power spectra for the single field slow-roll inflation, we derive the scalar spectral tilt n, and the tensor to scalar ratio r for the ...constant slow-roll inflation, and obtain the constraint on the slow-roll parameter ηfrom the Planck 2015 results. The inflationary potential for the constant slow-roll inflation is then reconstructed in the framework of both general relativity and the scalar-tensor theory of gravity, and compared with the recently reconstructed E model potential. In the strong coupling limit, we show that the η attractor is reached.
Contrary to conventional understanding, clean anatase {001} facets exhibit lower photoreactivity than {101} facets. Furthermore, the {010} facets showed the highest photocatalytic reactivity in ...generating OH radicals and hydrogen evolution. This behavior was revealed by studies on crystals grown hydrothermally to have a predominance of {001}, {101}, or {010} facets (left to right in picture (a) and (b)–(d), respectively).
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