Five phases of molybdenum carbide encapsulated by a boron–carbon–nitrogen (BCN) network are synthesized by decomposition of a Mo–imidazole-borate organometallic complex with slight variations in the imidazole-borate ligand structure The method relies on the restrained in situ carburization reaction between Mo atoms and imidazole-borate ligands on an atomic scale, thus generating molybdenum carbide nanoparticles encapsulated conformally by the BCN shell All phases of molybdenum carbide demonstrate excellent electrocatalytic hydrogen evolution reaction (HER) activity and stability in both acidic and basic electrolytes outperforming most of molybdenum carbides reported in the literature Hexagonal β-Mo2C@BCN consistently exhibits the most outstanding performance under all conditions The less active cubic α and hexagonal η phases also display enhanced HER activity and stability due to the promotional effect of the BCN shell The dual natured (electrophilic and nucleophilic) BCN layers can protect molybdenum carbide nanoparticles from corrosion and agglomeration, and improve their electrocatalytic activity by serving as an electron transfer medium and providing ample adsorption sites for water due to enhanced wetting properties

BCN network-encapsulated multiple phases of molybdenum carbide for efficient hydrogen evolution reactions in acidic and alkaline media

Ionic mobilities of monovalent cations in molten salt mixtures

The microscopic and macroscopic dynamics of calcium alkali nitrate melts are studied in their supercooled regime by means of shear rheology and nuclear magnetic resonance (NMR). The structural relaxation is probed using shear rheology to access the viscoelastic flow as well as using physical aging experiments. By exploiting the strongly quadrupole-perturbed 87Rb nucleus, the local dynamics is probed on the milliseconds to nanoseconds range using various NMR methods involving central-transition stimulated-echo techniques, line shape analyses, spin relaxations, and second-order dynamic shift effects. The time scales monitored via the local Rb probe are in harmony with the electrical conductivity relaxation times. The low-temperature NMR line shapes agree excellently with those predicted by the Czjzek model. The temperature dependent second-order dynamic frequency shift is described using the imaginary part of the spectral density. It is demonstrated how the latter quantity can be generalized to include effects of correlation time distributions.

Local and global dynamics of the viscous ion conductors 2Ca(NO3)2-3KNO3 and 2Ca(NO3)2-3RbNO3 probed by 87Rb nuclear magnetic resonance and shear rheology.

Dynamics of ions in molten LiOH has been investigated by molecular dynamics simulation analyzing the trajectories of the particles. Rotational autocorrelation function of the OH− ion shows rapid and large oscillatory decay at small t as well as rather slow and exponential decay at large t. The function agrees well with that obtained by polarized and depolarized Raman scattering measurements. The former decay was caused by libration of the OH− ion. The latter is based on the reorientation overlapping the relatively frequent libration. It is also found that the exponential decay has a strong correlation with the structural relaxation of the liquid. The OH− ion cannot rotate without any breakdown of the structure of the surrounding ions. Significantly oscillatory translational motions have been demonstrated in terms of various one‐particle and ensemble averaged autocorrelation functions. The spectrum analysis elucidated that there exists a strong correlation between the translational motion of the Li+ ion an...

Molecular dynamics studies on molten alkali hydroxides. II. Rotational and translational motions of ions in molten LiOH

Continuous recovery of concentrated solute from the melt by countercurrent electromigration

Internal cation mobilities in the binary system NaOH-KOH

Internal mobility ratios in the molten binary system KNO3- Ca0.5NO3 have been measured with the Klemm method in a range up to 50 mol% Ca0.5NO3. From these and available data on the densities and conductivities, the internal mobilities of K+ and Ca2+ ions (bK and bCa, respectively) have been calculated. With an increase of Ca2+ concentration, both bK and bCa decrease. The decrease of bK is presumed to be attributable to the “tranquillisation effect” caused by clustering of NO3- ions around Ca2+ ions due to the strong Coulombic interaction. The increase of bCa with increasing concentration o f K+ ions may be attributed to the agitation effect by K+ ions.

Internal Cation Mobilities in the Molten Binary System KNO3 — Ca(NO3)2

The relative differences in internal cation mobilities for the molten binary systems (K, Sr0.5)NO3 and (K, Ba0.5)NO3 have been measured with the Klemm method in the concentration range up to 34 mol% of the alkaline earth cations. From these and available data on the densities and conductivities, the internal mobilities of these cations, bK, bSr and bBa, have been calculated. In these systems bK and bSr or bBa decrease with decreasing concentration of the K+ ion. bK is well expressed by bK = fK ·bK*=fK·[A/(V-V0)] exp (-E/RT), where bK* is the internal mobility of the K+ ion in such melts as (K,Cs)NO3 in which the Coulombic attraction is the dominant factor for the internal mobility of the K+ ion, the constants A, V0, and E being independent of the coion, V is the molar volume of the present mixture and fK the volume fraction of KNO3 in the mixture. At a given mole fraction of K+ ions, the internal mobilities are in the order: Ca<Sr<Ba. This order could be interpreted as the decreasing order of the Coulombic attraction of these cations with the anion.

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Chao-cheng Yang

Papers

Internal cation mobilities in the binary system NaOH-KOH

Internal Cation Mobilities in the Molten Binary System KNO3 — Ca(NO3)2

Internal cation mobilities in the molten binary systems KNO3−Sr(NO3)2 and KNO3−Ba(NO3)2