Spherical porous iron-nitrogen-carbon nanozymes derived from a tannin coordination framework for the preparation of L-DOPA by emulating tyrosine hydroxylase.

L-3,4-Dihydroxyphenylalanine (L-DOPA) is widely used in Parkinson's disease treatment and is therefore in high demand. Development of an efficient method for the production of L-DOPA is urgently required. Nanozymes emulating tyrosine hydroxylase have attracted enormous attention for biomimetic synthesis of L-DOPA, but suffered from heterogeneity. Herein, a spherical porous iron-nitrogen-carbon nanozyme was developed for production of L-DOPA. Tannic acid chelated with ferrous ions to form a tannin-iron coordination framework as a carbon precursor. Iron and nitrogen co-doped carbon nanospheres were assembled via an evaporation-induced self-assembly process using urea as a nitrogen source, F127 as a soft template, and formaldehyde as a crosslinker. The nanozyme was obtained after carbonization and acid etching. The nanozyme possessed a dispersive iron atom anchored in the Fe-N coordination structure as an active site to mimic the active center of tyrosine hydroxylase. The material showed spherical morphology, uniform size, high specific surface area, a mesoporous structure and easy magnetic separation. The structural properties could promote the density and accessibility of active sites and facilitate mass transport and electron transfer. The nanozyme exhibited high activity to catalyze the hydroxylation of tyrosine to L-DOPA as tyrosine hydroxylase in the presence of ascorbic acid and hydrogen peroxide. The titer of DOPA reached 1.2 mM. The nanozyme showed good reusability and comparable enzyme kinetics to tyrosine hydroxylase with a Michaelis-Menten constant of 2.3 mM. The major active species was the hydroxyl radical. Biomimetic simulation of tyrosine hydroxylase using a nanozyme with a fine structure provided a new route for the efficient production of L-DOPA.

New Insight on Hydrogen Evolution Reaction Activity of MoP2 from Theoretical Perspective.

We systematically investigated the hydrogen evolution reaction (HER) of six facets of MoP2 based on the periodic density functional theory (DFT). The calculated values of Gibbs free energy of hydrogen adsorption (ΔGH) indicated that the (111) facet has a good HER activity for a large range of hydrogen coverages. The zigzagged patterns before 75% hydrogen coverage suggest a facilitation among Mo1, P1 and Mo2 sites, which are attributed to repeat occupancy sites of H atoms. From ab initial atomistic thermodynamics analysis of hydrogen coverage, we gained that the most stable coverage of hydrogen is 18.75% at 1 atm H2 and 298 K. Finally, the doping effects on HER activity were investigated and found that catalytic performance can be improved by substituting P with an S or N atom, as well as substituting the Mo atom with an Fe atom, respectively. We hope this work can provide new insights on further understanding of HER for MoP2 and give instructions for the experimental design and synthesis of transition metal phosphides (TMPs)-based high-performance catalysts.

Hydrogen evolution reaction activity related to the facet-dependent electrocatalytic performance of NiCoP from first principles.

Transition metal phosphides (TMPs) have been proven to act as highly active catalysts for the hydrogen evolution reaction (HER). Recently, single-phase ternary NiCoP electrocatalysts have been shown through experiments to display remarkable catalytic activity for the HER during water splitting. But, the inherent mechanism is not well understood. Herein, the HER activity of NiCoP with low-Miller-index facets, including (111), (100), (001)-NiP-t, and (001)-CoP-t, was systematically investigated using periodic density functional theory (DFT). The calculated Gibbs free energy of hydrogen adsorption (ΔG H) values reveal that all calculated facets have good catalytic activity for the HER. The (111) facet with the lowest surface energy in a vacuum has optimal ΔG H values close-to-zero for a range of hydrogen coverage. Ab initio thermodynamic analysis of hydrogen coverage was conducted to obtain the stabilities of surfaces, which follow the trend: (111) > (001)-CoP-t > (100) > (001)-NiP-t at 1 atm H2 and 298 K. We hope that this work can shed new light on further understanding the HER in relation to NiCoP and can give guidance for the design and synthesis of transition bimetal phosphide-based catalysts.

Facile three-step synthesis and photophysical properties of [8]-, [9]-, and [12]cyclo-1,4-naphthalene nanorings via platinum-mediated reductive elimination.

Herein we report a facile three-step synthesis of [8]-, [9]-, and [12]cyclo-1,4-naphthalene nanorings as the conjugated segments of carbon nanotubes. The nanorings were created via a platinum-mediated assembly of 1,4-naphthalene-based units and subsequent reductive elimination in the presence of triphenylphosphine. This present platinum-mediated approach is attractive because of its simple three-step process to produce the targeted nanorings in a high overall yield. In addition, their photophysical properties were studied using UV-vis spectroscopy and photoluminescence (PL) spectroscopy, which further revealed their unique size-dependent properties.

Pyrolyzed cobalt porphyrin-based conjugated mesoporous polymers as bifunctional catalysts for hydrogen production and oxygen evolution in water.

In this present study, a series of cobalt porphyrin-based conjugated mesoporous polymers (CoP-nph-CMP, n = 2, 3, 4) were fabricated as catalyst precursors to generate bifunctional catalysts via pyrolysis (CoP-nph-CMP-800, n = 2, 3, 4) for both the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER). Among these catalysts, CoP-2ph-CMP-800 exhibited the best catalytic activity with quite a low overpotential for both the OER (η = 370 mV for 10 mA cm-2) and the HER (η = 360 mV for 10 mA cm-2). Moreover, their excellent bifunctional catalytic performance was also explored in the overall water splitting test (η = 760 mV for 10 mA cm-2).