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Nanoscale zero-valent iron particles have large specific surface area and high reaction activity, and have been increasingly used for the degradation of environmental contaminants. However, rapid aggregation and deactivation hinder their wide applications. In this work, nanoscale zero-valent iron (NZVI) particles were prepared in vesicles, which were formed by self-assembly of amphiphilic block copolymer poly(1-vinylpyrrolidone-co-vinylacetate) (PVV) in aqueous tetrahydrofuran medium, and characterized with the aid of XRD, FTIR, SEM-EDX, TEM, XPS and DLS techniques. It was found that the NZVI particles were well encapsulated in the vesicles, and they could be stored directly in the air as solids, but the dried NZVI particles could be easily released from the vesicles once they were put in water. These NZVI particles showed some unique features, such as uniform nanometer size distribution (from 70 to 100 nm), vesicle-like morphology, and good dispersion. Activity and stability of the NZVI in vesicles were examined by using Cr(VI) and nitrobenzene as the model pollutants, and compared with the bare NZVI particles synthesized with the same procedures but without PVV. A dramatic difference in activity and stability was observed for the two different NZVI particles. The NZVI in vesicles showed a good chemical stability in the air, and still maintained its high reactivity in water. Such excellent performance might be attributed to the encapsulation of the NZVI by vesicles, which could impede well the strong agglomeration of metal particles in water and prevent metal particles from being oxidized in the air. [ABSTRACT FROM AUTHOR]

The concerted catalysis throughout multiple elementary steps is key to impel sluggish hydrogen evolution reaction (HER). Herein, NiMo/Mo 2 N/NC(500-R) array is constructed by embedding densely packed NiMo/Mo 2 N heterojunctions into nanorod skeleton of nitrogen-rich derived carbons (NC), then followed by electrochemical surface reconstruction. The great electrochemical surface area of resultant electrocatalyst implies fully-exposed concerted diatomic-ensembles. The ensemble effect of unique heteronanojunction induces charge polarizations between Mo and Ni species, gives pseudocapacitance comparable to supercapacitors, and pumps mass transfers to refresh entire HER process. The exceptional activity is demonstrated by ultra-low overpotentials of 5.8 and 200.6 mV respectively at 10 and 1000 mA cm−2, the impressive durability is indicated by lasting alkaline HER for 1000 h at 1 A cm−2. Moreover, the performances in water-alkali electrolyzer outperform most reported catalysts. This work presents valuable insights into concerted catalysis and designing efficient and durable electrocatalysts by ensemble effect from different metal heterojunctions for commercial applications. [Display omitted] • Well-separated heteronanojunctions impart the enhanced intrinsic activity to array. • Ensemble effect refreshes the concerted diatomic sites by charge polarizations. • Electrocatalyst delivers ultra-low overpotentials in alkaline hydrogen evolution. • Striking durability makes electrocatalyst commercializable in hydrogen production. • In-depth insights offer guidance to design efficient and durable electrocatalysts. [ABSTRACT FROM AUTHOR]