Jingyan Zhang

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.

Metallic Ni3N nanosheets with exposed active surface sites for efficient hydrogen evolution

Ni-Based catalysts have been considered as promising non-noble-metal hydrogen evolution reaction (HER) electrocatalysts for future clean energy devices. Here, atomically thin metallic Ni3N nanosheets are fabricated as the hydrogen evolution cathode, which exhibit remarkable HER activity close to that of a commercial Pt/C electrode. The Ni3N nanosheet catalyst shows an electrocatalytic current density of 100 mA cm2 at a low overpotential of 100 mV vs. RHE, a high exchange current density of 0.32 mA cm−2, a Tafel slope of 59.79 mV dec−1 and remarkable durability (little activity loss >5000 cycles) in acidic media as well as high HER activity in neutral and alkaline media. Through systematic theoretical calculations, the active surface sites of the Ni3N nanosheets are explicitly identified. The Ni atoms accompanied by surrounding N atoms on the N–Ni surface demonstrate a small ΔGH* of 0.065 eV due to the Ni–N co-effect, which act as the most active HER sites. This finding broadens our vision to realize the HER activity of 2D metallic electrocatalysts and paves the way for exciting opportunities in exploring and optimizing advanced catalysts for future energy production.

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.

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.

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...