•Ni-Co NWAs electrode was fabricated by polycarbonate template.•Ni-Co NWAs electrode with 10% of Co molar ratio shows best catalytic activity.•Direct urea/H2O2 fuel cell shows high output performance ...with Ni-Co NWAs anode.
Nickel-cobalt nanowire arrays (Ni-Co NWAs) electrode is prepared by one-step galvanostatic electrodeposition with a polycarbonate membrane as the template. By adjusting the Co proportion in the Ni and Co bath solution into 10%, the optimal Ni-Co NWAs electrode in terms of relatively lower onset potential and highest current density towards urea electro-oxidation is obtained. Its catalytic performance is investigated by constructing single direct urea/hydrogen peroxide (H2O2) fuel cell. Results show that a peak power density of 7.4mWcm−2 and an open circuit voltage of 0.92V are achieved at room temperature when 9.0molL−1 KOH and 0.33molL−1 urea are used as the anolyte, H2SO4 and H2O2 as the catholyte. Additionally, the urea/H2O2 fuel cell also demonstrates excellent stability during short term duration test.
A chiral iridium(I) N‐heterocyclic carbene complex was reported for the first time as the catalyst in the highly enantioselective intramolecular allylic amination reaction. The current method ...provides facile access to biologically important enantioenriched indolopiperazinones and piperazinones in good yields (74–91 %) and excellent enantioselectivities (92–99 % ee). Preliminary mechanistic investigations reveal that the C−H activation occurs at the position ortho to the N‐aryl group of the ligand.
A chiral iridium(I) N‐heterocyclic carbene complex catalyzes highly enantioselective intramolecular allylic amination reactions. This method provides facile access to biologically important enantioenriched indolopiperazinones and piperazinones in good yields. Mechanistic investigations reveal that the C−H activation occurs at the position ortho to the N‐aryl group of the ligand.
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•Both indirect oxidation and direct urea electro-oxidation paths exist on nickel.•Rate determining step depends on polarization potential and KOH concentration.•Nickel catalyst is ...poisoned by the CO2 intermediate.
Urea electro-oxidation reaction in alkaline medium is systematically analyzed by electrochemical impedance spectroscopy (EIS). The effects of polarization potential and KOH concentration on the impedance appearance are investigated. In the presence of urea, it is found that Nyquist plots exhibit two depressed semicircles, with one at higher frequencies stably locating in the first quadrant while the other’s location at lower frequencies varying between the first and second quadrant as the polarization potential changes. Results show both indirect and direct pathways proceed in urea electro-oxidation reaction. A mathematical model indicates the reverse loop in the Nyquist plots is attributed to CO2 poisoning on the catalyst, which is also validated by the followed chronoamperometric method. Moreover, the rate determining steps of urea electro-oxidation reaction is dependent on KOH concentration. The EIS technique gives a new sight to interpret the poor stability of urea electro-oxidation on nickel catalyst, and thus helps to explore a CO2-insensitive catalyst.
The Mongol–Okhotsk belt and adjacent areas are key areas to study the relationship between the Okhotsk and Paleo-Pacific tectonic regimes and their superposition on the older Paleo-Asian regimes ...during late Mesozoic times. This paper summarizes the spatial–temporal evolution of Late Mesozoic (Jurassic–Cretaceous) granitoids and related intrusions in these areas, and interprets the magmatic evolution in terms of a transition from contractional crustal thickening to extensional thinning. According to 407 published zircon ages, these granitoids were mainly emplaced during the intervals 200–180Ma, 180–165Ma, 165–145Ma, 145–135Ma and 135–100Ma. Jurassic granitoids (200–145Ma) predominately occur in the Baikal–NE Mongolia (BNEM) and Great Xing’an Range. Early Cretaceous (145–100Ma) granitoids are mainly occur in the Great Xing’an Range, and display a southward-younging migration. Significantly, Early Cretaceous granitoids also extend into the Trans-Baikal area across the Mongol–Okhotsk suture, far away from the Paleo-Pacific plate margin (in NE China); thus they were more plausibly related to post-orogenic collapse of the Mongol–Okhotsk orogen. From the Late Jurassic to Early Cretaceous, the granitoids evolved compositionally from calc-alkaline and high-K calc-alkaline, I-type, with some adakite-like features, to high-K calc-alkaline and shoshonitic, highly fractionated I-, transitional I-A or, A-type, characterized by a significant decrease in their Sr/Y ratios. This evolution coincided with a tectonic transition from contractional crustal thickening to extensional thinning. Combined with regional geology, we speculate that the Jurassic granitoids were likely derived from melting of the deep-seated, thickened lower continental crustal (LCC) sources, whereas the Cretaceous granitoids produced through crustal melting from an extensional thinning setting. Our results provide a case study demonstrating that the petrogenesis of granitic magmatism was closely associated with crustal tectonics. Early Jurassic granitoids along the Okhotsk belt formed in a subduction/collision setting related to closure of the Mongol–Okhotsk Ocean, whereas Late Jurassic granitoids in the Great Xing’an Range and in the northern North China Craton may have formed in a syn- or post-collisional setting superposed by far-field affects of subduction of the Paleo-Pacific plate. Early Cretaceous granitoids in these areas formed in response to post-orogenic extensional collapse of the Mongol–Okhotsk belt, coupled with back-arc extension related to Paleo-Pacific plate subduction.
Be dazzled by the sequence: The first efficient and general one‐pot method for the reductive bisalkylation of lactams/amides with Grignard and organolithium reagents has been developed (see scheme; ...DTBMP=2,6‐di‐tert‐butyl‐4‐methylpyridine, Tf=trifluoromethanesulfonyl).
A
bstract
We use Coulomb branch indices of Argyres-Douglas theories on
S
1
×
L
(
k,
1) to quantize moduli spaces
ℳ
H
of wild/irregular Hitchin systems. In particular, we obtain formulae for the “wild ...Hitchin characters” — the graded dimensions of the Hilbert spaces from quantization — for four infinite families of
ℳ
H
, giving access to many interesting geometric and topological data of these moduli spaces. We observe that the wild Hitchin characters can always be written as a sum over fixed points in
ℳ
H
under the U(1) Hitchin action, and a limit of them can be identified with matrix elements of the modular transform
ST
k
S
in certain two-dimensional chiral algebras. Although naturally fitting into the geometric Langlands program, the appearance of chiral algebras, which was known previously to be associated with Schur operators but not Coulomb branch operators, is somewhat surprising.
The α‐phosphanylferrocenecarbaldehyde (pS)‐1 was converted into the β‐styryl derivative (pS)‐4 by Wittig–Horner olefination. Subsequent hydroboration with Piers' borane HB(C6F5)2 followed by H2 ...splitting and crystallization gave the phosphonium/hydridoborate product (pS,R)‐5, which was used as a frustrated Lewis pair catalyst for the asymmetric hydrogenation of a series of imines (up to 69 % ee).
Asymmetric imine hydrogenation with a ferrocene‐based frustrated Lewis pair catalyst was achieved with up to 69 % ee.
In this report, graphene nanosheets (GNS)/nickel sulfide (NiS) based material for high-performance supercapacitor is prepared by "dip and dry" and electrodeposition methods. Commercial flexible ...make-up cottons (MCs) are chose as skeletons to construct homogeneous three-dimensional (3D) interconnected graphene-wrapped macro-networks, which can support structures for high loading of active electrode materials and facilitate the access of electrolytes to active electrode materials. The hybrid GNS/NiS based MCs (denoted as MCsatGNSatNiS) electrode yields relatively high specific capacitance of 775 F g super(-1) at a charge/discharge specific current of 0.5 A g super(-1) and good capacitance retention of 88.1% after 1000 cycles at 2 A g super(-1). Furthermore, the MCsatGNSatNiS electrode delivers a high energy density of 11.2 Wh kg super(-1) at even a high power density of 1008 W kg super(-1). Therefore, such low-cost and high-performance energy MCs based on GNS/NiS hierarchical nanostructures offer great promise in large-scale energy storage device applications.
The Friedel–Crafts type alkylation of C2-tethered thiophenes has been reported to be nonregioselective. Taking advantage of the highly regioselective 5-exo-trig spirocyclization of an ...electrochemically generated amidyl radical, we have unraveled an electrochemical dearomative spirocyclization of N-acyl thiophene-2-sulfonamides. Various nucleophilic agents, including carboxylates, alcohols, and fluoride, are readily incorporated to afford the remotely functionalized spirocyclic dihydrothiophenes, and their novel spirocyclic scaffolds have been shown to exhibit promising antitumor activities.
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