As a unique two-dimensional nanomaterial, layered black phosphorus (BP) nanosheets have shown promising applications in electronics. Although mechanical exfoliation was successfully used to prepare BP nanosheets, it is still a challenge to produce novel BP nanostructures in high yield. A facile top-down approach for preparation of black phosphorus quantum dots (BPQDs) in solution is presented. The obtained BPQDs have a lateral size of 4.9±1.6 nm and thickness of 1.9±0.9 nm (ca. 4±2 layers). As a proof-of-concept application, by using BPQDs mixed with polyvinylpyrrolidone as the active layer, a flexible memory device was successfully fabricated that exhibits a nonvolatile rewritable memory effect with a high ON/OFF current ratio and good stability.

N and S codoping of graphene is realized by a novel approach: covalent functionalization of graphene oxide using 2-aminothiophenol as a source of both N and S followed by thermal treatment. The resulting N- and S-codoped graphene has potential applications in high-performance lithium-ion batteries and as a metal-free catalyst for oxygen reduction reaction.

Nanostructured transition metal dichalcogenides (TMDs) are proven to be efficient and robust earth-abundant electrocatalysts to potentially replace precious platinum-based catalysts for the hydrogen evolution reaction (HER). However, the catalytic efficiency of reported TMD catalysts is still limited by their low-density active sites, low conductivity, and/or uncleaned surface. Herein, a general and facile method is reported for high-yield, large-scale production of water-dispersed, ultrasmall-sized, high-percentage 1T-phase, single-layer TMD nanodots with high-density active edge sites and clean surface, including MoS , WS , MoSe , Mo W S , and MoSSe, which exhibit much enhanced electrochemical HER performances as compared to their corresponding nanosheets. Impressively, the obtained MoSSe nanodots achieve a low overpotential of -140 mV at current density of 10 mA cm , a Tafel slope of 40 mV dec , and excellent long-term durability. The experimental and theoretical results suggest that the excellent catalytic activity of MoSSe nanodots is attributed to the high-density active edge sites, high-percentage metallic 1T phase, alloying effect and basal-plane Se-vacancy. This work provides a universal and effective way toward the synthesis of TMD nanostructures with abundant active sites for electrocatalysis, which can also be used for other applications such as batteries, sensors, and bioimaging.

Five-fold-twinned PtCu nanoframes (NFs) with nanothorns protruding from their edges are synthesized by a facile one-pot method. Compared to commercial Pt/C catalyst, the obtained highly anisotropic five-fold-twinned PtCu NFs show enhanced electrocatalytic performance toward the oxygen reduction reaction and methanol oxidation reaction under alkaline conditions.

A general and facile method for water-dispersed noble metal (Au, Ag, Pd, Pt) nanocrystal modified MoS2 nanosheets (NM-MoS2 NSs) has been developed. By using sodium carboxymethyl cellulose as a stabilizer, well-dispersed NM-MoS2 NSs with homogeneously deposited noble metal nanocrystals (NM NCs) can be synthesized in aqueous solutions. Due to the transition from the semiconducting 2H phase to the metallic 1T phase, the chemically exfoliated MoS2 (ce-MoS2) NSs have improved electrochemical activity. The partially metallic nature of the ce-MoS2 NSs and the catalytic activity of the NM NCs synergistically make NM-MoS2 NSs a potential electrochemical catalyst. For the first time, Pd-MoS2 NSs were used as an electrocatalyst for methanol oxidation in alkaline media. The results showed that Pd-MoS2 NSs have enhanced catalytic activity with 2.8-fold anodic peak current mass density compared to a commercial Pd/C catalyst, suggesting potential for application in direct methanol fuel cells (DMFCs).

from detaching from the graphene surface during the charge/ discharge process, thus resulting in good rate capability and long cycle life. [ 12 ] Recently, metal-organic frameworks (MOFs) have attracted increasing research interest. [ 13 ] In particular, MOFs have been demonstrated as versatile templates and precursors for the synthesis of various porous nanomaterials, [ 14 ] which hold great promise for high-performance electrode materials of energystorage devices. [ 14d,h ] For instance, by using MOFs of MIL-88-Fe, we recently prepared composites of porous Fe 2 O 3 -coated 3D graphene networks, which exhibited excellent performance in lithium-ion batteries. [ 15 ] To the best of our knowledge, there is no report on preparation of graphene-wrapped metal oxides by using MOFs as the precursor.Here, for the fi rst time, we report a novel and convenient way to fabricate the reduced graphene oxide (rGO)-wrapped MoO 3 , referred to as rGO/MoO 3 , by simply mixing molybdenum-based MOFs, [ 16 ] i.e., Mo-MOFs ( Figure S1, Supporting Information), with graphene oxide (GO) sheets followed by the annealing process ( Scheme 1 ). The obtained porous rGO/ MoO 3 composite was then used as the electrode material for fabrication of all-solid-state, fl exible, symmetric supercapacitor devices.Scheme 1 illustrates the preparation of the rGO/MoO 3 composite. Typically, the Mo-MOFs ( Figure S1, Supporting Information) were fi rst mixed with GO aqueous solution to obtain the GO-wrapped Mo-MOFs (GO/Mo-MOFs, Step 1), which was then subjected to a two-step annealing process under Ar and air, respectively, to prepare the rGO-wrapped MoO 3 composite (rGO/MoO 3 ) (Step 2 and 3). During the annealing process, the rGO-wrapped MoO 2 composite (rGO/MoO 2 ) was obtained by annealing GO/Mo-MOFs under an Ar atmosphere (Step 2) since GO was simultaneously thermally reduced to rGO in this step. After the subsequent annealing of rGO/MoO 2 in air, the rGO/MoO 3 composite was obtained (Step 3).Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images of the obtained GO/Mo-MOFs composite clearly indicate that a thin layer of GO sheets with a thickness of ≈20 nm was coated on the surface of Mo-MOFs ( Figure S2A,B, Supporting Information). Compared to the relatively smooth surface of Mo-MOFs ( Figure S1, Supporting Information), many wrinkles and ripples of GO sheets were observed on GO/Mo-MOFs ( Figure S2A,B, Supporting Information), suggesting the successful coating of GO sheets on Mo-MOFs. The X-ray diffraction (XRD) spectra confi rmed the Adv. Mater. 2015, 27, 4695-4701 www.advmat.de www.MaterialsViews.com Adv. Mater. 2015, 27, 4695-4701 www.advmat.de www.MaterialsViews.com Scheme 1. Schematic illustration of the preparation of rGO/MoO 3 composite by using Mo-MOFs as precursor.

No abstract

A facile, one-pot solvothermal method is developed to synthesize MoS2 nanoflowers (MoS2NFs) coated on reduced graphene oxide (rGO) paper. The resulting MoS2NF/rGO paper serves as a freestanding, flexible and durable working electrode for hydrogen evolution reaction (HER), exhibiting an overpotential lowered to -0.19 V with a Tafel slope of ∼95 mV per decade.