Peitao Liu

N-doped WS2 nanosheets: a high-performance electrocatalyst for the hydrogen evolution reaction

Non-Pt-based catalysts are urgently required to produce abundant hydrogen in electrochemical water splitting, in order to make the hydrogen evolution reaction (HER) feasible and energy efficient. Here, N-doped WS2 nanosheets were synthesized by a one step sol–gel process, which are electrochemically active toward the HER with a low onset potential of 86 mV, a large cathodic current density (100 mA cm−2 at an overpotential of 197 mV) and long-term durability. We anticipate that this synthetic method will be a powerful tool for creating high-performance electrocatalysts from other transition metal dichalcogenides.

Flower-like N-doped MoS2 for photocatalytic degradation of RhB by visible light irradiation.

In this paper, the photocatalytic performance and reusability of N-doped MoS2 nanoflowers with the specific surface area of 114.2 m(2) g(-1) was evaluated by discoloring of RhB under visible light irradiation. Results indicated that the 20 mg fabricated catalyst could completely degrade 50 ml of 30 mg l(-1) RhB in 70 min with excellent recycling and structural stability. The optimized N-doped MoS2 nanoflowers showed a reaction rate constant (k) as high as 0.06928 min(-1) which was 26.4 times that of bare MoS2 nanosheets (k = 0.00262). In addition, it was about seven times that of P25 (k = 0.01) (Hou et al 2015 Sci. Rep. 5 15228). The obtained outstanding photocatalytic performance of N-doped MoS2 nanoflowers provides potential applications in water pollution treatment, as well as other related fields.

Atomically Thin B doped g-C3N4 Nanosheets: High-Temperature Ferromagnetism and calculated Half-Metallicity

Since the graphitic carbon nitride (g-C4N3), which can be seen as C-doped graphitic-C3N4 (g-C3N4), was reported to display ferromagnetic ground state and intrinsic half-metallicity (Du et al., PRL,108,197207,2012), it has attracted numerous research interest to tune the electronic structure and magnetic properties of g-C3N4 due to their potential applications in spintronic devices. In this paper, we reported the experimentally achieving of high temperature ferromagnetism in metal-free ultrathin g-C3N4 nanosheets by introducing of B atoms. Further, first-principles calculation results revealed that the current flow in such a system was fully spin-polarized and the magnetic moment was mainly attributed to the p orbital of N atoms in B doped g-C3N4 monolayer, giving the theoretic evidence of the ferromagnetism and half-metallicity. Our finding provided a new perspective for B doped g-C3N4 spintronic devices in future.

Copper dopants improved the hydrogen evolution activity of earth-abundant cobalt pyrite catalysts by activating the electrocatalytically inert sulfur sites

Cobalt pyrite (CoS2) is considered to be a promising catalyst for the hydrogen evolution reaction (HER) due to its intrinsic metallicity and high catalytic activity. However, the catalytically inert S-sites and sluggish reaction kinetics severely impede its commercial application. Herein, combining systematic theoretical and experimental approaches, a highly active and stable Cu doped CoS2 catalyst for the HER is demonstrated. Cu dopants are proven to not only reduce the hydrogen adsorption free energy (ΔGH*) of the Co sites from 0.41 eV to −0.13 eV, but also arouse the inert S sites with the low ΔGH* of −0.11 eV. A large cathode current density (10 mA cm−2 at 52 mV), low Tafel slope (42 mV dec−1), large exchange current density (0.68 mA cm−2), and good stability were observed in the Co0.93Cu0.07S2 catalyst, which are better than those found for the previously reported CoS2-based catalysts. The success of improving the electrochemical performance via the introduction of Cu dopants offers new opportunities in the development of high performance CoS2-based electrodes for other energy-related applications.

P dopants induced ferromagnetism in g-C3N4 nanosheets: Experiments and calculations

Outstanding magnetic properties are highly desired for two-dimensional (2D) semiconductor nanosheets due to their potential applications in spintronics. Metal-free ferromagnetic 2D materials whose magnetism originated from the pure s/p electron configuration could give a long spin relaxation time, which plays the vital role in spin information transfer. Here, we synthesize 2D g-C3N4 nanosheets with room temperature ferromagnetism induced by P doping. In our case, the Curie temperature of P doped g-C3N4 nanosheets reaches as high as 911 K and the precise control of the P concentration can further adjust the saturation magnetization of the samples. First principles calculation results indicate that the magnetic moment is primarily due to strong hybridization between p bonds of P, N, and C atoms, giving the theoretical evidence of the ferromagnetism. This work opens another door to engineer a future generation of spintronic devices.Outstanding magnetic properties are highly desired for two-dimensional (2D) semiconductor nanosheets due to their potential applications in spintronics. Metal-free ferromagnetic 2D materials whose magnetism originated from the pure s/p electron configuration could give a long spin relaxation time, which plays the vital role in spin information transfer. Here, we synthesize 2D g-C3N4 nanosheets with room temperature ferromagnetism induced by P doping. In our case, the Curie temperature of P doped g-C3N4 nanosheets reaches as high as 911 K and the precise control of the P concentration can further adjust the saturation magnetization of the samples. First principles calculation results indicate that the magnetic moment is primarily due to strong hybridization between p bonds of P, N, and C atoms, giving the theoretical evidence of the ferromagnetism. This work opens another door to engineer a future generation of spintronic devices.

Phase-transfer induced room temperature ferromagnetic behavior in 1T@2H-MoSe2 nanosheets

Manipulating electronic and magnetic properties of two-dimensional transitional-metal dichalcogenides has raised a lot of attention recently. Herein we report the synthesis and ferromagnetic properties of phase-transfer induced room temperature ferromagnetic behavior in 1 T@2H-MoSe2 nanosheets. Experimental results indicate the saturated magnetization of the 1 T@2H-MoSe2 compound increases first and then decreases as the increasing of 1 T-MoSe2 phase, where 65.58% 1 T-MoSe2 phase incorporation in 2H-MoSe2 could enhance the saturated magnetization from 0.32 memu/g to 8.36 memu/g. Besides, obvious magnetoresistance behaviors are observed in these samples, revealing their potential applications in future spintronics.

Efficient visible light-induced degradation of rhodamine B by W(NxS1-x)(2) nanoflowers

Here, W(NxS1−x)2 nanoflowers were fabricated by simple sintering process. Photocatalytic activity results indicated our fabricated N-doped WS2 nanoflowers shown outstanding photoactivity of degradating of rhodamine B with visible light. Which is attributed to the high separation efficiency of photoinduced electron–hole pairs, the broadening of the valence band (VB), and the narrowing of energy band gap. Meanwhile, our work provided a novel method to induce surface sulfur vacancies in crystals by introduing impurities atoms for enhancing their photodegradation.

Anion vacancy-mediated ferromagnetism in atomic-thick Ni3N nanosheets

Realizing spin and electronic behavior of two-dimensional ultrathin nanosheets is significant to construct next generation nanoelectronics. Here, atomic-thick Ni3N nanosheets with clear room temperature ferromagnetism and high saturation magnetization (1.2 emu/g) are reported. X-ray magnetic circular dichroism and first-principles calculation results give the evidence that the observed intrinsic ferromagnetism in Ni3N nanosheets originates from the surface N-deficiency, where alignments of localized large magnetic moments of Ni in the vicinity of the N defect can be aligned parallel to activate macroscopic ferromagnetism. These ultrathin Ni3N nanosheets show great potential application in next-generation electron devices.

Re doping induced 2H-1T phase transformation and ferromagnetism in MoS2 nanosheets

In this paper, Re-doped MoS2 nanosheets were synthesized by a facile hydrothermal reaction and an annealing process. Through structural characterization, it was observed that the doping of Re could lead to 2H-1T transformation in both the Re and Mo coordinating structures, and the 1T ratios of Mo and Re atoms increased with the Re-doping concentration. Hysteresis loops demonstrated intrinsic room temperature ferromagnetism in the Re-doped MoS2 nanosheets, and the value of saturated magnetization reached 8 memu/g when the doping concentration of Re was 17.12 at. %. The magnetic properties resulted from the increasing net magnetic moments of Re atoms and 1T-coordinated Mo atoms. Additionally, the 1T-incorporated 2H structure and magnetism were thermally stable in these samples. These results explored a new path for MoS2 nanosheets to be applied in spintronic devices in the future.In this paper, Re-doped MoS2 nanosheets were synthesized by a facile hydrothermal reaction and an annealing process. Through structural characterization, it was observed that the doping of Re could lead to 2H-1T transformation in both the Re and Mo coordinating structures, and the 1T ratios of Mo and Re atoms increased with the Re-doping concentration. Hysteresis loops demonstrated intrinsic room temperature ferromagnetism in the Re-doped MoS2 nanosheets, and the value of saturated magnetization reached 8 memu/g when the doping concentration of Re was 17.12 at. %. The magnetic properties resulted from the increasing net magnetic moments of Re atoms and 1T-coordinated Mo atoms. Additionally, the 1T-incorporated 2H structure and magnetism were thermally stable in these samples. These results explored a new path for MoS2 nanosheets to be applied in spintronic devices in the future.

Resistive switching effect of N-doped MoS2-PVP nanocomposites films for nonvolatile memory devices

Resistive memory technology is very promising in the field of semiconductor memory devices. According to Liu et al, MoS2-PVP nanocomposite can be used as an active layer material for resistive memory devices due to its bipolar resistive switching behavior. Recent studies have also indicated that the doping of N element can reduce the band gap of MoS2 nanosheets, which is conducive to improving the conductivity of the material. Therefore, in this paper, we prepared N-doped MoS2 nanosheets and then fabricated N-doped MoS2-PVP nanocomposite films by spin coating. Finally, the resistive memory [C. Tan et al., Chem. Soc. Rev. 44, 2615 (2015)], device with ITO/N-doped MoS2-PVP/Pt structure was fabricated. Study on the I-V characteristics shows that the device has excellent resistance switching effect. It is worth mentioning that our device possesses a threshold voltage of 0.75 V, which is much better than 3.5 V reported previously for the undoped counterparts. The above research shows that N-doped MoS2-PVP nano...