Bifunctional Heterostructured Transition Metal Phosphides for Efficient Electrochemical Water Splitting

Reducing green hydrogen production costs is essential for developing a hydrogen economy. Developing cost‐effective electrocatalysts for water electrolysis is thus of great research interest. Among various material candidates, transition metal phosphides (TMP) have emerged as robust bifunctional electrocatalysts for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) due to their various phases and tunable electronic structure. Recently, heterostructured catalysts have exhibited significantly enhanced activities toward HER/OER. The enhancement can be attributed to the increased amount of accessible active sites, accelerated mass/charge transfer, and optimized adsorption of intermediates, which arise from the synergistic effects of the heterostructure. Herein, a comprehensive overview of the recent progress of bifunctional TMP‐based heterostructure is introduced to provide an insight into their preparation and corresponding reaction mechanisms. It starts with summarizing general fundamental aspects of HER/OER and the synergistic effect of heterostructures for enhanced catalytic activity. Next, the innovational strategies to design and construct bifunctional TMP‐based heterostructures with enhanced overall water splitting activity, as well as the related mechanisms, are discussed in detail. Finally, a summary and perspective for further opportunities and challenges are highlighted for the further development of bifunctional TMP‐based heterostructures from the points of practical application and mechanistic studies.     

When is an interacting particle system ergodic?

We consider stochastic flip dynamics for an infinite number of Ising spins on the lattice ^d . We find a sequence of constructive criteria for the system to be exponentially ergodic. The main idea is to approximate the continuous time process with discrete time processes (itsEuler polygon) and to use an improved version of previous results [MS] about constructive ergodicity of discrete time processes.     

Ergodicity of probabilistic cellular automata: A constructive criterion

We give a sequence of criteria (of increasing complexity) for the exponential ergodicity of discrete time interacting particle systems. Each criterion involves estimating the dependence on initial conditions of the process on finite space-time volumes. It generalizes and improves the existing single site condition and is the analog of the Dobrushin-ShlosmanC _v condition in equilibrium statistical mechanics. Our dynamic criterion may also be used to prove the uniqueness of Gibbs state in situations where theC _v condition fails. As a converse we prove that if there is a certain form of convergence to the stationary measure faster thann ^–d , wheren is the time andd is the dimension of the lattice, then our condition holds for some space-time volumes and hence the convergence must be exponentially fast.     

Enzymatic resolution of chiral phosphinate esters

The bacterial phosphotriesterase has been shown to catalyze the stereoselective hydrolysis of phosphinate esters. The wild-type enzyme preferentially hydrolyzes the SP-enantiomers of methyl phenyl p-X-phenylphosphinate esters by 3 orders of magnitude. The mutant enzyme, I106T/F132A/H254G/H257W, exhibits the opposite stereoselectivity and hydrolyzes the RP-enantiomer up to 30 times faster than the corresponding SP-enantiomer. The enantiomerically pure phosphinate esters, prepared from the kinetic resolution of racemic mixtures, can serve as the entry point for the chemoenzymatic preparation of P-chiral phosphines and phosphine oxides.     

Human Cell Encapsulation in Gel Microbeads with Cosynthesized Concentric Nanoporous Solid Shells

Encapsulation of therapeutic cells in core–shell microparticles has great promise for the treatment of a range of health conditions. Unresolved challenges related to control of the particle morphology, mechanical stability, and immunogenicity hinder dissemination of this promising approach. Here, a novel polymer material for cell encapsulation and a combined novel, easy to control, synthesis method are introduced. Core–shell cell encapsulation is demonstrated with a concentric core–shell morphology formed during a single UV exposure, resulting in particles that consist of a synthetic hydrogel core of polyethylene glycol diacrylate and a solid, but porous, shell of off‐stoichiometric thiol‐ene. The encapsulated human cells in 100 µm diameter particles have >90% viability. The average shell thickness is controlled between 7 and 13 µm by varying the UV exposure, and the shell is measured to be permeable to low molecular weight species (<180 Da) but impermeable to higher molecular weight species (>480 Da). The unique material properties and the orthogonal control of the microparticle core size, shell thickness, shell permeability, and shell surface properties address the key unresolved challenges in the field, and are expected to enable faster translation of novel cell therapy concepts from research to clinical practice.     

Simultaneous analysis of gamma-hydroxybutyric acid and its precursors in urine using liquid chromatography-tandem mass spectrometry

We have developed a rapid method that enables the simultaneous analysis of gamma-hydroxybutyrate (GHB) and its precursors, i.e. gamma-butyrolactone (GBL) and 1,4-butanediol (1,4-BD) in urine. The method comprised a simple dilution of the urine sample, followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. Chromatographic separation was achieved using an Atlantis dC18 column, eluted with a mixture of formic acid and methanol. The method was linear from 1-80 mg/L for GHB and 1,4-BD and from 1-50 mg/L for GBL. The limit of quantification was 1 mg/L for all analytes. The procedure, which has a total analysis time (including sample preparation) of less than 12 min, was fully validated and applied to the analysis of 182 authentic urine samples; the results were correlated with a previously published GC-MS procedure and revealed a low prevalence of GHB-positive samples. Since no commercial immunoassay is available for the routine screening of GHB, this simple and rapid method should prove useful to meet the current increased demand for the measurement of GHB and its precursors.     

Matrix-isolation FT-IR spectroscopic study and theoretical DFT(B3LYP)/6-31++G** calculations of the vibrational and conformational properties of tyrosine

The complicated conformational isomerism of tyrosine is studied by experimental matrix-isolation FT-IR spectroscopy combined with theoretical DFT(B3LYP)/6-31++G** calculations. Not less than 18 possible conformations of tyrosine have been considered theoretically. The results revealed that the most and the less stable forms of neutral tyrosine have the same conformation of the main part of amino acid (conformation II) but they differ in orientation of the phenyl ring. The calculated values of the relative energies suggest that all conformations would be detectable in the experimental spectrum. However, it appeared that it is not possible to distinguish in the experimental spectrum between the bands due to the forms with the same conformation of the main part of amino acid but a different orientation of the phenol ring.     

Blue shifting hydrogen bonding in the complexes of chlorofluoro haloforms with acetone-d(6) and oxirane-d(4)

Mixtures of haloforms of the type HCClnF3-n (n = 0-3) with oxirane-d4 and acetone-d6 have been studied in liquid krypton, using infrared spectroscopy. Analysis of the spectra shows that a small fraction of the monomers is transformed into 1:1 complexes in which the haloform C-H bond is hydrogen bonded to the oxygen atom of the base. For all complexes, the haloform CH stretch is blue shifted, with the shift increasing from chloroform to fluoroform, while the ratio of the infrared intensities of the C-H stretching bands of complexed and free C-H bonds changes from a value well over 50 for the chloroform to a value near 0.1 for the fluoroform complexes. These observations have been corroborated by ab initio calculations using CP-corrected gradient techniques.     

meso-Dichloropyrimidinyl substituted expanded porphyrins

Condensation of 4,6-dichloro-2-phenylpyrimidine-5-carbaldehyde with pyrrole enables the synthesis of a number of expanded porphyrins of which the [26]hexaphyrin was easily isolated and successfully converted into the decasubstituted doubly N-fused hexaphyrin variant.