Nitrogen fixation by alkali and alkaline earth metal hydrides assisted by plasma.

The chemical behaviors of alkali and alkaline earth metal hydrides including LiH, KH, MgH, CaH, and BaH under nitrogen plasma differ significantly from one another, exhibiting an ammonia production trend that contrasts with that observed under thermal conditions. A prominent feature of KH is its ability to facilitate plasma-assisted N fixation without generating H byproduct, showing high atomic economy in utilization of hydride ions for N reduction.

Light-Driven De/Rehydrogenation of a LiH Surface under Ambient Conditions.

Lithium hydride (LiH), a saline hydride with a hydrogen density of 12.6 wt %, is highly thermostable, which hinders its extensive application in hydrogen storage. In this study, we demonstrate a distinct photodecomposition of LiH under ambient conditions.

Behavior of Lithium Amide Under Argon Plasma.

Alkali and alkaline earth metal amides are a type of functional materials for hydrogen storage, thermal energy storage, ion conduction, and chemical transformations such as ammonia synthesis and decomposition. The thermal chemistry of lithium amide (LiNH), as a simple but representative alkali or alkaline earth metal amide, has been well studied previously encouraged by its potentials in hydrogen storage. In comparison, little is known about the interaction of plasma and LiNH.

Light-driven ammonia synthesis under mild conditions using lithium hydride.

Photon-driven chemical processes are usually mediated by oxides, nitrides and sulfides whose photo-conversion efficiency is limited by charge carrier recombination. Here we show that lithium hydride undergoes photolysis upon ultraviolet illumination to yield long-lived photon-generated electrons residing in hydrogen vacancies, known as F centres. We demonstrate that photon-driven dehydrogenation and dark rehydrogenation over lithium hydride can be fulfilled reversibly at room temperature, which is about 600 K lower than the corresponding thermal process.

Barium hydride activates Ni for ammonia synthesis catalysis.

Nickel (Ni) metal has long been considered to be far less active for catalytic ammonia synthesis as compared to iron, cobalt, and ruthenium. Herein, we show that Ni metal synergized with barium hydride (BaH) can catalyse ammonia synthesis with an activity comparable to that of an active Cs-Ru/MgO catalyst typically below 300 °C. Kinetic analyses show that the addition of BaH makes the apparent activation energy for the Ni catalyst decrease dramatically from 150 kJ mol to 87 kJ mol.

In situ formed Co from a Co-Mg-O solid solution synergizing with LiH for efficient ammonia synthesis.

A cobalt magnesium oxide solid solution (Co-Mg-O) supported LiH catalyst has been synthesized, in which LiH functions both as a strong reductant for the in situ formation of Co metal nanoparticles and a key active component for ammonia synthesis catalysis. Dispersion of the Co-LiH composite on the Co-Mg-O support results in a significantly higher ammonia synthesis rate under mild reaction conditions (19 mmol g h at 300 °C, 10 bar).

Thermodynamic Properties of Ammonia Production from Hydrogenation of Alkali and Alkaline Earth Metal Amides.

Thermodynamic properties of alkali and alkaline earth metal amides are critical for their performance in hydrogen storage as well as catalytic ammonia synthesis. In this work, the ammonia equilibrium concentrations of LiNH , KNH and Ba(NH ) at ca.10 bar of hydrogen pressure and different temperatures were measured by using a high-pressure gas-solid reaction system equipped with a conductivity meter.

Alkali and Alkaline Earth Hydrides-Driven N Activation and Transformation over Mn Nitride Catalyst.

Early 3d transition metals are not focal catalytic candidates for many chemical processes because they have strong affinities to O, N, C, or H, etc., which would hinder the conversion of those species to products. Metallic Mn, as a representative, undergoes nitridation under ammonia synthesis conditions forming bulk phase nitride and unfortunately exhibits negligible catalytic activity.