Single‐atom nickel dopants anchored to three‐dimensional nanoporous graphene can be used as catalysts of the hydrogen evolution reaction (HER) in acidic solutions. In contrast to conventional ...nickel‐based catalysts and graphene, this material shows superior HER catalysis with a low overpotential of approximately 50 mV and a Tafel slope of 45 mV dec−1 in 0.5 M H2SO4 solution, together with excellent cycling stability. Experimental and theoretical investigations suggest that the unusual catalytic performance of this catalyst is due to sp–d orbital charge transfer between the Ni dopants and the surrounding carbon atoms. The resultant local structure with empty C–Ni hybrid orbitals is catalytically active and electrochemically stable.
Single‐atom nickel dopants anchored to three‐dimensional nanoporous graphene show superior catalytic activities towards the hydrogen evolution reaction (HER) in acidic solutions. Experimental and theoretical investigations suggest that the unusual catalytic performance of this catalyst is due to sp–d orbital charge transfer between the Ni dopants and the surrounding carbon atoms.
Bicontinuous nanoporous N‐doped graphene with tunable pore size is synthesized by nanoporous Ni‐based chemical vapor deposition. The novel 3D graphene material shows an outstanding catalytic activity ...towards the oxygen reduction reaction with a low onset potential of −0.08 V and a high kinetic current density of 8.2 mA cm−2 at −0.4 V.
We report three‐dimensional (3D) nanoporous graphene with preserved 2D electronic properties, tunable pore sizes, and high electron mobility for electronic applications. The complex 3D network ...comprised of interconnected graphene retains a 2D coherent electron system of massless Dirac fermions. The transport properties of the nanoporous graphene show a semiconducting behavior and strong pore‐size dependence, together with unique angular independence. The free‐standing, large‐scale nanoporous graphene with 2D electronic properties and high electron mobility holds great promise for practical applications in 3D electronic devices.
A nickel for your graphene: The title material was synthesized by chemical vapor deposition using nanoporous nickel. The 3D nanoporous graphene preserves 2D electronic properties, such as high electron mobility and massless Dirac fermions.
A binder‐free self‐grown oxy‐hydroxide@nanoporous Ni‐Mn hybrid electrode with high capacitance and cyclic stability is fabricated by electrochemical polarization of a dealloyed nanoporous Ni‐Mn ...alloy. Combined with the low material costs, high electrochemical stability, and environmentally friendly nature, this novel electrode holds great promise for applications in high‐capacity commercial supercapacitors.
Nanoporous Ni with a tunable nanopore size and chemical compositions was fabricated by dealloying a Ni30Mn70 precursor alloy at various temperatures. The influence of electrochemical parameters on ...the formation of large-scale nanoporous Ni was systematically investigated. Different from the fabrication of nanoporous noble metals (Au, Pt and Pd), the dealloying of Ni30Mn70 includes three kinetically competitive processes: dissolution of Mn, interface diffusion of Ni and dissolution of Ni. The nanopore size and residual Mn can be tailored by controlling the dealloying time, temperature and applied potential. The as-dealloyed nanoporous Ni with a large internal surface area, excellent conductivity and naturally formed oxide surface can be directly used as a free-standing electrode for electrochemical supercapacitors with a high capacitance and excellent cycling stability.
Nanoporous metals produced by dealloying have shown great promise in many areas such as catalysis/electrocatalysis, energy conversion/storage, sensing/biosensing, actuation, and surface-enhanced ...Raman scattering. Particularly, nanoscale metal ligaments with high electronic conductivity, tunable size and rich surface chemistry make nanoporous metals very promising as catalysts/electrocatalysts for energy conversion applications such as fuel cells and also as versatile three-dimensional substrates for energy-storage in supercapacitors and lithium ion batteries. In this review, we focus on the recent developments of dealloyed nanoporous metals in both catalysis/electrocatalysis and energy storage. In particular, based on the state-of-the-art electron microscopy characterization, we explain the atomic origin of the high catalytic activity of nanoporous gold. We also highlight the recent advances in rationally designing nanoporous metal-based composites and hierarchical structures for enhanced energy storage. Finally, we conclude with some outlook and perspectives with respect to future research on dealloyed nanoporous metals in catalysis- and energy-related applications.
Structure insight of dealloyed nanoporous metals and the relationship of structure and applications in catalysis and energy storage/conversion are highlighted.
Hierarchical nanoporous metals with a large surface area and rich pore channels are the sought-after nanostructure for many applications. Here we report a two-step dealloying approach to fabricate a ...hierarchical nanoporous Ni alloy by utilizing the chemical stability difference of the constituent elements in a multicomponent precursor. Due to the large surface area and high electric conductivity, the hierarchical nanoporous Ni alloy exhibits a high specific areal capacitance of ∼1.11Fcm−2 and volumetric capacitance of 317Fcm−3.
We report a simple approach to fabricate aligned bimetallic Pt–Cu microwires with a three-dimensional nanoporous structure, tunable composition, and high catalytic activity by dealloying a dilute ...Pt3Cu97 precursor. Each microwire possesses inherent ultrafine nanoporous structure with uniformly distributed Pt–Cu alloy ligaments and nanopores with a dimension of ∼2 nm. Electrochemical measurements manifest that the nanoporous Pt–Cu microwires have significantly enhanced electrocatalytic activities compared with a commercial Pt/C nanoparticulate catalyst. With evident advantages of facile preparation and enhanced catalytic performance together with low material costs, the nanoporous Pt–Cu microwires hold great promise as a high-performance catalyst for electrochemical energy conversion.
Coffee bioactive components include caffeine, chlorogenic acids (CGAs), trigonelline, tryptophan alkaloids, diterpenes and other secondary metabolites. During roasting, coffee metabolites undergo ...complex Maillard reactions, producing melanoidins and other degradation products, the most controversial among which is acrylamide, an ingredient widely found in baked food and listed as a second class carcinogen. Green and roasted coffee ingredients have good biological activities for the prevention of cardiovascular disease, and antibacterial, anti-diabetic, neuroprotection, and anti-cancer activities. To better understand the relationship between coffee ingredients and human health, and to effectively use the active ingredients, it is essential to understand the sources of coffee active ingredients and their mechanisms of action in the organism. This paper systematizes the available information and provides a critical overview of the sources of coffee active ingredients and the mechanisms of action
in vivo
or
in vitro
, and their combined effects on common human diseases.
The sources and mechanism of action of coffee active ingredients are detailed and their joint roles in the prevention of common human diseases are summarized.
Despite considerable efforts over the past decade, only 34 fast radio bursts-intense bursts of radio emission from beyond our Galaxy-have been reported
. Attempts to understand the population as a ...whole have been hindered by the highly heterogeneous nature of the searches, which have been conducted with telescopes of different sensitivities, at a range of radio frequencies, and in environments corrupted by different levels of radio-frequency interference from human activity. Searches have been further complicated by uncertain burst positions and brightnesses-a consequence of the transient nature of the sources and the poor angular resolution of the detecting instruments. The discovery of repeating bursts from one source
, and its subsequent localization
to a dwarf galaxy at a distance of 3.7 billion light years, confirmed that the population of fast radio bursts is located at cosmological distances. However, the nature of the emission remains elusive. Here we report a well controlled, wide-field radio survey for these bursts. We found 20, none of which repeated during follow-up observations between 185-1,097 hours after the initial detections. The sample includes both the nearest and the most energetic bursts detected so far. The survey demonstrates that there is a relationship between burst dispersion and brightness and that the high-fluence bursts are the nearby analogues of the more distant events found in higher-sensitivity, narrower-field surveys
.
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