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Benefiting from improved electrical conductivity, the N-doped MoSe 2 nanosheets show substantially enhanced HER activity with a lower onset overpotential of approximately −135 mV and a smaller Tafel slope of 62 mV dec −1 , which exhibiting enhanced catalytic performance compared with that of pure MoSe 2 . The success of improving the HER performance via the introduction of N dopant offers a new opportunity in the development of high performance MoSe 2 -based electrocatalyst. [ABSTRACT FROM AUTHOR]

Cost-effective materials for electrocatalytic water splitting are key to renewable energy research. In this work, MoS 2 /sulfur and nitrogen co-doped reduced graphene oxide (SNG) nanocomposite was produced via a two-step hydrothermal process. The formation of nanocomposite was confirmed by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM). It is found that the MoS 2 /SNG nanocomposite exhibits much higher catalytic activity for the hydrogen evolution reaction (HER) relative to MoS 2 and MoS 2 /RGO catalysts, as manifested by much larger cathodic current density with smaller overpotential of −120 mV and lower Tafel slope of 45 mV dec −1 . It is believed that the outstanding performance is attributed to the high electronic conductivity of SNG for fast charge transport. This study highlights the significance of the strong electronic coupling effect between the MoS 2 and SNG in the enhancement of HER electrocatalytic activity. [ABSTRACT FROM AUTHOR]

By taking advantage of large specific surface area and large number of reaction sites of the 2D WS 2 nanosheet (NS), we developed a simple adsorption-photoreduction method to load Pt nanoparticles (NPs) on the NS carrier. The WS 2 NSs were soaked in KPtCl 4 solution for sufficient amount of time to ensure the adsorption equilibrium of the Pt ions on the WS 2 NS substrate. Upon photolysis and H 2 post-treatment, uniformly dispersed Pt 0 NPs (∼2 nm in size) were harvested. The hybrid structure containing 0D Pt 0 NPs and 2D WS 2 thin-layers showed distinctly enhanced electrocatalytic activity for hydrogen evolution reaction (HER) with the overpotential at a current density of 10 mA cm −2 reduced to 80 mV compared with commercial Pt/C electrode. The synergetic effect of 0D and 2D structures may encourage designing new catalysts systems for special application. [ABSTRACT FROM AUTHOR]

Since the revelation of significant negative thermal expansion (NTE) across an extensive temperature range in cubic ScF 3 , there has been a notable surge of interest in fluorides of the ReO 3 -type structure. However, with the exceptions of ScF 3 , nearly all ReO 3 -type fluorides at low temperature crystallize in a rhombohedral structure in which the thermal expansion becomes strong positive. In this work, we reinvestigated the phase transition mechanism of α -AlF 3 from rhombohedral to cubic phase by combining in situ X-ray diffraction, in situ Raman spectra and first principles calculation. Our research has unveiled that this phase transition is driven by a phonon mode A 1g , which is associated with the tilting of octahedral structures. The α -AlF 3 shows seriously anharmonic lattice dynamics with A 1g phonon mode exhibiting softening behavior even far below the transition temperature. Anharmonic analysis based on Balkanski model suggests that A 1g mode decays into a longitudinal acoustic (LA) phonon and a transverse optical phonon E g , which have large amplitudes and promote the titling of AlF 6 octahedra, final leading to the phase transition to the cubic structure. This finding further indicates the potential for tuning NTE materials through phonon engineering. • Computational and experimental reinvestigation of the temperature-induced phase transition mechanism of α-AlF 3. • Anharmonic analysis of the Balkanski model shows that the phase transition is mainly driven by an anharmonic phonon (A 1g). • Possible decay paths for the A 1g mode include longitudinal acoustic (LA) phonons and transverse optical E g phonons. [ABSTRACT FROM AUTHOR]

Using a dual buffer structure, a controlled layer-by-layer deposition process has been developed to fabricate a monolayer Pt coating on carbon fiber with complex network structures. The electrochemical quartz crystal microbalance, current density analyses, and X-ray photoelectron spectroscopy results conclude that the monolayer deposition process accomplishes full coverage on the substrate and that the thickness of the deposition layer can be controlled on a single atom scale. It is found that a dual buffer, comprising a thin Ni coating and an Au nano-film, is necessary to cover carbon fiber substrate to ensure a complete monolayer Pt coverage. Moreover, the Pt monolayer is found to work better than thicker Pt – the best norm in the field, for catalyzing hydrogen evolution reaction. [ABSTRACT FROM AUTHOR]