Fusheng Wen

Flexible All-Solid-State Supercapacitors based on Liquid-Exfoliated Black-Phosphorus Nanoflakes.

Flexible all-solid-state supercapacitors are fabricated with liquid-exfoliated black-phosphorus (BP) nanoflakes as an electrode material. These devices deliver high specific volumetric capacitance, power density, and energy density, up to 13.75 F cm(-3) , 8.83 W cm(-3) , and 2.47 mW h cm(-3) , respectively, and an outstanding long life span of over 30 000 cycles, demonstrating the excellent performance of the BP nanoflakes as a flexible electrode material in electrochemical energy-storage devices.

Te‐Doped Black Phosphorus Field‐Effect Transistors

Element doping allows manipulation of the electronic properties of 2D materials. Enhanced transport performances and ambient stability of black-phosphorus devices by Te doping are presented. This provides a facile route for achieving airstable black-phosphorus devices.

Enhanced Photoresponse of SnSe-Nanocrystals-Decorated WS2 Monolayer Phototransistor

Single-layer WS2 has shown excellent photoresponse properties, but its promising applications in high-sensitivity photodetection suffer from the atomic-thickness-limited adsorption and band-gap-limited spectral selectivity. Here we have carried out investigations on WS2 monolayer based phototransistors with and without decoration of SnSe nanocrystals (NCs) for comparison. Compared to the solely WS2 monolayer, SnSe NCs decoration leads to not only huge enhancement of photoresponse in visible spectrum but also extension to near-infrared. Under excitation of visible light in a vacuum, the responsivity at zero gate bias can be enhanced by more than 45 times to ∼99 mA/W, and the response time is retained in millisecond level. Particularly, with extension of photoresponse to near-infrared (1064 nm), a responsivity of 6.6 mA/W can be still achieved. The excellent photoresponse from visible to near-infrared is considered to benefit from synergism of p-type SnSe NCs and n-type WS2 monolayer, or in other words, the formed p-n heterojunctions between p-type SnSe NCs and n-type WS2 monolayer.

Fabrication of NiCo2-Anchored Graphene Nanosheets by Liquid-Phase Exfoliation for Excellent Microwave Absorbers

Graphene nanosheets (GNSs) were prepared by an efficient liquid-phase exfoliation method, and then the NiCo2/GNS nanohybrids were fabricated using the single-mode microwave-assisted hydrothermal technique. The NiCo2/GNS composites with different GNS proportions were investigated as microwave absorbers. Morphology investigation suggested that NiCo2 nanocrystals were uniformly anchored on the GNS without aggregation. The electromagnetic parameters of NiCo2/GNS nanohybrids could be artificially adjusted by changing the GNS proportion, which led to an exceptional microwave-absorbing performance. A reflection loss (RL) exceeding -20 dB was obtained in the frequency range of 5.3-16.4 GHz for the absorber thicknesses of 1.2-3.2 mm, while an optimal RL of -30 dB was achieved at 11.7 GHz for a thickness of 1.6 mm. The enhanced microwave-absorbing performance indicated that the NiCo2/10 wt % GNS composite has great potential for use as an excellent microwave absorber.

Gate tunable MoS2–black phosphorus heterojunction devices

Heterojunctions are essential building blocks for modern electronic and optoelectronic devices. The recent discovery of two-dimensional semiconductors offers an opportunity to build these heterojunctions with atomic sharp interfaces by van der Waals interaction. Here we fabricated MoS2–black phosphorus (BP) heterojunction devices. Due to the narrow band-gap and unpinned Fermi level of BP, this heterojunction could be tuned to either p–n or n–n by the electrostatic gating. The current rectification behaviors were observed in both p–n and n–n junctions. The current rectification of the MoS2–BP n–n junction was attributed to the energy barrier formed at the interface of wide band-gap MoS2 and narrow band-gap BP. The gate dependence of forward current, reverse current and current rectification properties of the heterojunction at different thickness scale were systematically studied, suggesting the electrical properties of the heterojunction could be controlled by designing the thickness of MoS2 and BP flake.

Synthesis of peanut-like hierarchical manganese carbonate microcrystals via magnetically driven self-assembly for high performance asymmetric supercapacitors

To construct a suitable structure for both electronic conduction and ionic transport towards supercapacitors, peanut-like hierarchical manganese carbonate (MnCO3) microcrystals assembled with floss-like nanowires are synthesized via a hydrothermal process and primarily used as an active material for supercapacitors. The formation mechanism is illustrated by means of a dissolution–recrystallization process and magnetically driven self-assembly. The electrode with peanut-like hierarchical MnCO3 microcrystals exhibits a high specific capacitance of 293.7 F g−1 and a superior cycle stability of 71.5% retention after 6000 cycles, which are higher than those of the reported Mn-based active materials in alkaline electrolytes. The asymmetric supercapacitor, assembled with the peanut-like MnCO3 electrode as the positive electrode and a home-made porous carbon electrode as the negative electrode, exhibits an energy density of 14.7 W h kg−1 at a power density of 90.2 W kg−1 and an energy density of up to 11.0 W h kg−1 at 3.3 kW kg−1. An as-assembled all-solid-state supercapacitor series can light up a LED indicator for 10 min, indicating a promising practical application of peanut-like MnCO3 microcrystals.

Carbonaceous photonic crystals as ultralong cycling anodes for lithium and sodium batteries

Via carbonization of butterfly wings, carbonaceous photonic crystals (CPCs) were derived as anode materials for lithium and sodium ion batteries (LIB and NIB) with ultralong cycling stability. Owing to the CPCs inheritance of the wings unique photonic structure, the periodically interconnected ridges and ribs serve as perfect channels for electron transportation and allow the presence of cross-linked macropores for facile electrolyte access and ion diffusion. The carbonization-induced micro- and mesopores in the ridges and ribs can further facilitate electrolyte penetration and thus shorten the ion diffusion distances. Moreover, depending on the carbonization temperature, rich contents of O and N heteroatoms on the carbon surfaces can offer extra sites for reversible Li+/Na+ adsorption and enhance the electrochemical reactivity and electronic conductivity. For LIB/NIB applications, the derived CPC (CPC800) by carbonization at 800 °C delivers the best performances. CPC800 offers high specific capacities of 590 mA h g−1 (LIB) and 235 mA h g−1 (NIB) with ∼100% coulombic efficiencies at 0.05 A g−1. More impressively, CPC800 displays ultralong cycling stability for LIB and NIB applications, sustaining more than 10000 cycles at 5 A g−1 (LIB) and 1 A g−1 (NIB) with no evident observation of the fading of capacity and ∼100% coulombic efficiencies.

Drastic time-dependent decrease in the saturation magnetization observed in Pd/Co/Pd trilayers with perpendicular anisotropy

In the Pd/Co/Pd trilayer with magnetic perpendicular anisotropy, it has been found that both the saturation magnetization MS and the coercivity HC demonstrate a drastic time-dependent decrease. The time-dependent effect has been observed to be strongly related to the Co layer thickness. When the Co layer is thinner, the drops of HC and MS become much faster with time. The observed time-dependent effect is attributed to absorption of gaseous elements (for example, hydrogen) during exposure of the sample to the air, which can induce the reduction in Pd-polarization.

Flexible Black-Phosphorus Nanoflake/Carbon Nanotube Composite Paper for High-Performance All-Solid-State Supercapacitors

We proposed a simple route for fabrication of the flexible BP nanoflake/carbon nanotube (CNT) composite paper as flexible electrodes in all-solid-state supercapacitors. The highly conductive CNTs not only play a role as active materials but also increase conductivity of the hybrid electrode, enhance electrolyte shuttling and prevent the restacking between BP nanoflakes. The fabricated flexible all-solid-state supercapacitor (ASSP) device at the mass proportion of BP/CNTs 1:4 was found to deliver the highest volumetric capacitance of up to 41.1 F/cm3 at 0.005 V/s, superior to the ASSP based on the bare graphene or BP. The BP/CNTs (1:4) device delivers a rapid charging/discharging up to 500 V/s, which exhibits the characteristic of a high power density of 821.62 W/cm3, while having outstanding mechanical flexibility and high cycling stability over 10 000 cycles (91.5% capacitance retained). Moreover the BP/CNTs (1:4) ASSP device still retains large volumetric capacitance (35.7 F/cm3 at the scan rate of 0.005 V/s) even after 11 months. In addition, the ASSP of BP/CNTs (1:4) exhibits high energy density of 5.71 mWh/cm3 and high power density of 821.62 W/cm3. As indicated in our work, the strategy of assembling stacked-layer composites films will open up novel possibility for realizing BP and CNTs in new-concept thin-film energy storage devices.

{111}-specific twinning structures in nonstoichiometric ZrC0.6 with ordered carbon vacancies

Twinning structures in ordered nonstoichiometric ZrC0.6 have been investigated experimentally and theoretically. Via transmission electron microscopy and selected area electron diffraction measurements, {111}-specific twins have been observed. Interestingly, two special types of twinning interfaces, i.e. (111)C and (111)Zr interfaces, are recognized to be formed as a result of the presence of ordered carbon vacancies. In contrast to the high stacking fault energy for twinning formation in stoichiometric ZrC, first-principles calculations indicate that the presence of ordered carbon vacancies leads to a great reduction in the twinning interfacial energy, thus favouring the stabilization of twinning structures in the ordered ZrC0.6.