Enhanced hydrogen sorption kinetics of magnesium by destabilized MgH2−δ

Enhancing the Combustion of Magnesium Nanoparticles via Low-Temperature Plasma-Induced Hydrogenation

The hydrogenation of metal nanoparticles provides a pathway toward tuning their combustion characteristics. Metal hydrides have been employed as solid-fuel additives for rocket propellants, pyrotechnics, and explosives. Gas generation during combustion is beneficial to prevent aggregation and sintering of particles, enabling a more complete fuel utilization. Here, we discuss a novel approach for the synthesis of magnesium hydride nanoparticles based on a two-step aerosol process. Mg particles are first nucleated and grown via thermal evaporation, followed immediately by in-flight exposure to a hydrogen-rich low-temperature plasma. During the second step, atomic hydrogen generated by the plasma rapidly diffuses into the Mg lattice, forming particles with a significant fraction of MgH2. We find that hydrogenated Mg nanoparticles have an ignition temperature that is reduced by ∼200 °C when combusted with potassium perchlorate as an oxidizer, compared to the non-hydrogenated Mg material. This is due to the release of hydrogen from the fuel, jumpstarting its combustion. In addition, characterization of the plasma processes suggests that a careful balance between the dissociation of molecular hydrogen and heating of the nanoparticles must be achieved to avoid hydrogen desorption during production and achieve a significant degree of hydrogenation.

The Catalytic Role of D-block Elements and Their Compounds for Improving Sorption Kinetics of Hydride Materials: A Review

The goal of finding efficient and safe hydrogen storage material motivated researchers to develop several materials to fulfil the demand of the U.S. Department of Energy (DOE). In the past few years, several metal hydrides, complex hydrides such as borohydrides and alanates, have been researched and found efficient due to their high gravimetric and volumetric density. However, the development of these materials is still limited by their high thermodynamic stability and sluggish kinetics. One of the methods to improve the kinetics is to use catalysts. Among the known catalysts for this purpose, transition metals and their compounds are known as the leading contender. The present article reviews the d-block transition metals including Ni, Co, V, Ti, Fe and Nb as catalysts to boost up the kinetics of several hydride systems. Various binary and ternary metal oxides, halides and their combinations, porous structured hybrid designs and metal-based Mxenes have been discussed as catalysts to enhance the de/rehydrogenation kinetics and cycling performance of hydrogen storage systems.

Modelling and evaluation of hydrogen desorption kinetics controlled by surface reaction and bulk diffusion for magnesium hydride

The ‘shrinking core’ model has been applied for the evaluation of hydrogen desorption kinetics during decomposition of magnesium hydride.

A prospect for LiBH4 as on-board hydrogen storage

In contrast to the traditional metal hydrides, in which hydrogen storage involves the reversible hydrogen entering/exiting of the host hydride lattice, LiBH4 releases hydrogen via decomposition that produces segregated LiH and amorphous B phases. This is obviously the reason why lithium borohydride applications in fuel cells so far meet only one requirement — high hydrogen storage capacity. Nevertheless, its thermodynamics and kinetics studies are very active today and efficient ways to meet fuel cell requirements might be done through lowering the temperature for hydrogenation/dehydrogenation and suitable catalyst. Some improvements are expected to enable LiBH4 to be used in on-board hydrogen storage.

High-pressure and high-temperature differential scanning calorimeter for combined pressure-concentration-temperature measurements of hydrides

The design and construction of a high-pressure (200 bar) and high-temperature (600 degrees C) heat-flow differential scanning calorimeter (DSC) for the in situ investigation of the hydrogenation and dehydrogenation reactions of hydrides is presented. In combination with a pressure-concentration-temperature (pcT) system, simultaneous thermodynamic and volumetric measurements become accessible. Due to the high thermal conductivity of hydrogen, only the sample cell and the reference cell are exposed to hydrogen and the remaining system is under ambient conditions. This separation has the advantage that the calibration factor is independent of the hydrogen pressure. The internal empty volume of the combined system is as low as possible to maximize the precision of the pcT measurements. The calorimetric block of the DSC is designed with a silver/copper alloy and the temperature measurements are made resistively with platinum temperature sensors (Pt 100). The instrument was calibrated and its operability was successfully studied on the example of the hydrogen sorption behavior of LaNi(5).