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Hydrogen has become an indispensable aspect of sustainable energy resources due to depleting fossil fuels and increasing pollution. Since hydrogen storage and transport is a major hindrance to expanding its applicability, green ammonia produced by electrochemical method is sourced as an efficient hydrogen carrier. Several heterostructured electrocatalysts are designed to achieve significantly higher electrocatalytic nitrogen reduction (NRR) activity for electrochemical ammonia production. In this study, we controlled the nitrogen reduction performances of Mo2C-Mo2N heterostructure electrocatalyst prepared by a simple one pot synthesis method. The prepared Mo2C-Mo2N0.92 heterostructure nanocomposites show clear phase formation for Mo2C and Mo2N0.92, respectively. The prepared Mo2C-Mo2N0.92 electrocatalysts deliver a maximum ammonia yield of about 9.6 μg h-1 cm-2 and a Faradaic efficiency (FE) of about 10.15%. The study reveals the improved nitrogen reduction performances of Mo2C-Mo2N0.92 electrocatalysts due to the combined activity of the Mo2C and Mo2N0.92 phases. In addition, the ammonia production from Mo2C-Mo2N0.92 electrocatalysts is intended by the associative nitrogen reduction mechanism on Mo2C phase and by Mars-van-Krevelen mechanism on Mo2N0.92 phase, respectively. This study suggests the importance of precisely tuning the electrocatalyst by heterostructure strategy to substantially achieve higher nitrogen reduction electrocatalytic activity.

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The structures of the subnanometer clusters of CdS that form in zeolite Y (FAU), prepared as follows, have been determined. A single crystal of Cd 2+ -exchanged zeolite Y was prepared by the exchange of Na 75 −Y (|Na 75 |[Si 117 Al 75 O 384]−Y with aqueous Cd(NO 3 ) 2 at 294 K, followed by vacuum dehydration at 723 K (crystal 1). A second crystal, similarly prepared, was exposed to 6.7 × 10 4 Pa of dry H 2 S(g) for 6 h at 294 K and evacuated (crystal 2). Their structures were determined crystallographically using synchrotron X-rays and were refined using all data to the final error indices (calculated using only0.040/0.156 and 0.049/0.186, respectively. In crystal 1, Cd 2+ ions primarily occupy sites I and II. In crystal 2, |Cd 27 (Cd 4 S 6+ ) 0.6 (Cd-(SHCd) 4 6+ ) 0.9 H 12 |[Si 117 Al 75 O 384 ]−FAU, tetrahedral Cd 4 S 6+ ions center about 7.5% of the sodalite cavities and tetrahedral Cd(SHCd) 4 6+ ions center about 11% of the supercages. In Cd(SHCd) 4 6+, a Cd 2+ ion at the center of a supercage bonds tetrahedrally to four SH − ions, each of which bonds in turn to an 8-ring Cd 2+ ion. Of the 36.5(9) Cd 2+ ions per unit cell (indicating complete or nearly complete Cd 2+ exchange) before treatment with H 2 S(g), only 6.9 participate in the above clusters. Most, 27, remain uncomplexed, and 2.6 have left the zeolite as CdS(s). No neutral clusters of formula Cd n S n are present within the zeolite.

Seven single crystals of fully dehydrated Ni2+-exchanged zeolite Y (Si/Al = 1.56) were prepared via cation exchange of Na75–Y (|Na75|[Si117Al75O384]-FAU) by flowing 0.05 M aqueous solutions of Ni­(NO3)2·6H2O (pH 4.9 and 294 K) with various ion-exchange times. Their crystal structures were completely determined by single-crystal synchrotron X-ray diffraction techniques in cubic space group Fd3̅m at 100(1) K. In all seven structures, Ni2+ ions occupy sites I, I′, and II, and sometimes site II′ or a second site II, or both, preferring site I; residual Na+ ions in crystals 1 and 2 are found at site III and/or a second site III. The level of Ni2+ exchange monotonically increased from 75.2 to 89.6% [from 28.2(2) to 33.6(8) Ni2+ ions per unit cell] with increasing exchange time until 18 h. The dealumination of the zeolite frameworks was observed in the center of sodalite cavities after 24 h, suggesting that this process occurs during ion exchange, or subsequent dehydration. H+ ions are present in all seven crystals for a charge balance. Both the unit cell constants and Na+ contents decreased with increasing levels of Ni2+ exchange and ion-exchange time.