Molybdenum (Mo)-based compounds with properly engineered nanostructures usually possess improved reversible lithium storage capabilities, which offer great promise to boost the performance of lithium-ion batteries (LIBs). Nevertheless, a lack of efficient and high-yield methods for constructing rational nanostructures has largely restricted the application of these potentially important materials. Herein we demonstrate a metal-organic frameworks (MOFs) mediated strategy to successfully synthesize a series of one-dimensional Mo-based/carbon composites with distinct nanostructures. In this process, starting from well-designed MoO nanorods, the crystal control growth is first proposed that a layer of MOFs is achieved to be controllably grown on surfaces of MoO, forming an obvious core-shell structure, and then the adopted precursor can be in situ transformed into MoO or MoC which are both well confined in conductive porous carbons through direct carbonization at different temperatures, where the MOFs shell serve as both carbon sources and the reactant to react with MoO simultaneously. Benefiting from this design, all optimized products exhibit enhanced electrochemical performances when evaluated as anode materials for LIBs, especially the hollow MoO/C and core-shell MoC/C electrodes, show best reversible capacities up to 810 and 530 mAh g even after 600 cycles at a current density of 1 A g, respectively. So this work may broaden the application of MOFs as a kind of coating materials and elucidates the attractive lithium storage performances of molybdenum-based compounds.
Designing economical and high-efficiency electrocatalysts for overall water splitting is urgently needed but remains a long and arduous task. Herein, we synthesized hydrotalcite-like Ni(OH) nanosheets growing on Ni foam (Ni(OH)/NF) via a facile one-pot hydrothermal method. With the assistance of a rotating oven, Ni(OH) nanosheets demonstrate a regular hexagonal morphology and homogeneous distribution. The resultant Ni(OH)/NF electrode shows superior electrocatalytic activity and durability for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), as well as the overall water splitting. The Ni(OH)/NF electrode delivers 20 mA·cm at an overpotential of 172 mV for HER, 50 mA·cm at an overpotential of 330 mV for OER, and 10 mA·cm at a cell voltage of 1.68 V for water electrolysis in 1.0 M KOH. The present study demonstrates a feasible and effective strategy to prepare highly efficient electrocatalysts for water electrolysis.
The broadband light-absorption ability of carbon dots (CDs) has inspired their application in photocatalysis, however this has been impeded by poor electron transfer inside the CDs. Herein, we report the preparation of Cu-N-doped CDs (Cu-CDs) and investigate both the doping-promoted electron transfer and the performance of the CDs in photooxidation reactions. The Cu-N doping was achieved through a one-step pyrolytic synthesis of CDs with Na2 [Cu(EDTA)] as precursor. As confirmed by ESR, FTIR, and X-ray photoelectron spectroscopies, the Cu species chelates with the carbon matrix through Cu-N complexes. As a result of the Cu-N doping, the electron-accepting and -donating abilities were enhanced 2.5 and 1.5 times, and the electric conductivity was also increased to 171.8 μs cm(-1) . As a result of these enhanced properties, the photocatalytic efficiency of CDs in the photooxidation reaction of 1,4-dihydro-2,6-dimethylpyridine-3,5-dicarboxylate is improved 3.5-fold after CD doping.
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