Baorui Xia

Enhanced hydrogen evolution catalysis in MoS2 nanosheets by incorporation of a metal phase

Here, we propose a metal 1T-phase incorporation strategy to dramatically enhance the hydrogen evolution reaction (HER) catalysis in primitive 2H-MoS2 nanosheets. Electrochemical measurement results indicate the fabricated 1T@2H-MoS2/C nanosheets exhibit facile electrode kinetics, low-loss electrical transport and possess a proliferated density of catalytic active sites compared to that of 2H-MoS2. As an electrocatalyst operating at a current density of 10 mA cm−2, the fabricated 1T@2H-MoS2/C nanosheets exhibited overpotentials of 64 mV in 0.5 M H2SO4, as well as a Tafel slope of 49 mV per decade, which exceed by far the activity of previous MoS2 catalysts. This design opens up new possibilities for effective manipulation of HER catalysts in two-dimensional nanostructures.

High temperature ferromagnetism in Cu-doped MoS2 nanosheets

The synthesis of 2D metal chalcogenide based on ferromagnetic nanosheets is in high demand for modern electronics and spintronics applications. Herein, Cu-doped MoS2 nanosheets were successfully prepared by a hydrothermal method. Magnetic measurement results indicate that the doping of Cu ions can introduce ferromagnetism into MoS2 nanosheets, where saturate magnetization increases with increased Cu concentration. Further, the hysteresis curves measured at different temperatures demonstrate a high Curie temperature of 930 K for the Cu-doped MoS2 nanosheets. This result opens a new path to exploring spintronics in pristine 2D nanostructures by non-magnetic atom doping.

Activation of the MoSe2 basal plane and Se-edge by B doping for enhanced hydrogen evolution

We demonstrate by both calculation and experiments the effective B doping-induced activation of both the basal plane and Se-edge in vertically aligned MoSe2 flakes, and the disruptive enhancement in the electrocatalytic hydrogen evolution reaction. The B doping boosts drastically the catalytic activity of MoSe2 for the hydrogen evolution reaction compared to the undoped one, characterized by a low overpotential (84 mV) and Tafel slope (39 mV s−1), which are comparable to those of the best Pt/C electrode. The realization of activation for both the basal plane and Se-edge by B doping in MoSe2 shows an innovative pathway towards the activity enhancement of TMDs for electrocatalysts and energy storage.

Hierarchical ultrathin Mo(SxSe1−x)2 nanosheets with tunable ferromagnetism and efficient hydrogen evolution reaction activity: towards defect site effect

Layered transition metal dichalcogenides (TMDs) are now playing important roles in both fundamental studies and technological applications due to their special structures and rich physical properties. Here, hierarchical ultrathin TMD nanosheets based on molybdenum sulphoselenides [Mo(SxSe1−x)2] with tunable ferromagnetism were synthesized by a one step hydrothermal method. In addition, the hierarchical ultrathin Mo(SxSe1−x)2 nanosheets exhibit excellent composition-dependent electrocatalytic properties for the hydrogen evolution reaction (HER). It is considered that the intrinsic ferromagnetism and the efficient HER activity are related to the defect sites in the samples. This finding opens up a way to alter the ferromagnetism and electroactivity of layered chalcogenides by fine tuning of the composition.

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.

Adjustable ferromagnetic behavior in iron-doped two-dimensional MoS2 multilayer nanosheets

Robust ferromagnetism of two-dimensional (2D) semiconductors has been achieved in recent years. In this study, 2D MoS2 nanosheets doped with Fe ions were prepared and characterized. The results indicated that the prepared samples had no other impurities induced by Fe doping. M–H curves measured under different temperatures suggested that robust ferromagnetism occurred in the MoS2 nanosheets after Fe doping and that the nanosheets had a high Curie temperature above 930 K. This experiment provides an effective method for manipulating the magnetic properties of MoS2 nanosheets via doping with Fe ions.

Dual‐Native Vacancy Activated Basal Plane and Conductivity of MoSe2 with High‐Efficiency Hydrogen Evolution Reaction

Although transition metal dichalcogenide MoSe2 is recognized as one of the low-cost and efficient electrocatalysts for the hydrogen evolution reaction (HER), its thermodynamically stable basal plane and semiconducting property still hamper the electrocatalytic activity. Here, it is demonstrated that the basal plane and edges of 2H-MoSe2 toward HER can be activated by introducing dual-native vacancy. The first-principle calculations indicate that both the Se and Mo vacancies together activate the electrocatalytic sites in the basal plane and edges of MoSe2 with the optimal hydrogen adsorption free energy (ΔGH* ) of 0 eV. Experimentally, 2D MoSe2 nanosheet arrays with a large amount of dual-native vacancies are fabricated as a catalytic working electrode, which possesses an overpotential of 126 mV at a current density of 100 mV cm-2 , a Tafel slope of 38 mV dec-1 , and an excellent long-term durability. The findings pave a rational pathway to trigger the activity of inert MoSe2 toward HER and also can be extended to other layered dichalcogenide.

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.

Argon ion irradiation induced phase transition and room temperature ferromagnetism in the CuO thin film

We have deposited a copper oxide (CuO) thin film using a magnetron sputtering system by modulating rate of oxygen flow, and we found that the phase of cuprous oxide (Cu2O) appeared after irradiation by argon ions. Magnetic measurement results indicate that the thin film exhibits room temperature ferromagnetism after irradiation, while the virgin CuO thin film is diamagnetic. Vacancies and interstitial would appear in the lattice during irradiation and phase transition, which will originate in the local magnetic moment. In combination with the analyses of Raman spectra, we believe that the ferromagnetism of the film may originate from Cu vacancies, which provides an approach in investigating the mechanism of magnetism in the diluted magnetic semiconductor.

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.