Highly active and durable catalyst for hydrogen generation by the NaBH4 hydrolysis reaction: CoWB/NF nanodendrite with an acicular array structure

Magnesium hydride (MgH2) has a high hydrogen storage capacity (7.6 wt%) and the Mg element is abundant on the earth. Due to its strong reduction ability, even at room temperature it can provide the hydrogen yield reaching 15.2 wt% H (1703 mL/g) when interacting with water, which makes it very attractive for the application in supplying hydrogen for autonomous H energy systems. However, the hydrolysis reaction is rapidly inhibited by the Mg(OH)2 passivation layer formed on the surface of MgH2. In order to remove the passivation film and improve the efficiency of the MgH2 hydrolysis process, several methods including alloying, ball milling, changing the aqueous solution, have been successfully utilized. In this paper the process of hydrolysis of magnesium hydride in aqueous solutions of MgCl2 used as a promotor of the interaction has been studied in detail. It was found that the initial hydrolysis rate, pH of the reaction mixture, and overall reaction yield are all linearly dependent of the logarithm of MgCl2 concentration. It has been shown that pH of the reaction mixture in the presence of MgCl2 is well described by considering a system “weak base and its salt with strong acid” type buffer solution. Reference data for this hydrolysis reaction were also carefully analyzed. The mechanism and the kinetic model of the process of MgH2 hydrolysis in water solutions involved passivation of the MgH2 surface by the formed Mg(OH)2 precipitate followed by its repassivation have been proposed. The obtained after the hydrolysis reactions precipitates were studied using XRD and EDS. It was found also that the final products of reaction consist of Mg(OH)2 (brucsite type) and remaining MgH2. This fact shows that the formation of solid species such as MgCl2 xMgO yH2O at the studied conditions is unlikely and decreasing of pH the reaction mixture has a different nature.

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Mg-based composites as effective materials for storage and generation of hydrogen for FC applications

10.15407/materials2021.053 ◽

2021 ◽

pp. 53-80

Author(s):

D. Korablev ◽

◽

A. Bezdorozhev ◽

V. Yartys ◽

J. Solonin ◽

...

Keyword(s):

Hydrogen Storage ◽

Hydrogen Generation ◽

High Energy ◽

High Energy Density ◽

Hydrolysis Reaction ◽

Preparation Technique ◽

Power Sources ◽

Safety Issues ◽

Renewable Power ◽

Physical And Chemical

Today, hydrogen is considered as an ideal choice for storing and carrying energy produced by renewable power sources since it is renewable, eco-friendly and has a high energy density. However, due to the low hydrogen storage capacity, high cost and safety issues of the conventional storage methods, several challenges need to be resolved to effectively use hydrogen in mobile applications. Solid-state hydrogen storage in atomic form in hydrides is a promising method of storage for this purpose, particularly because a double amount of hydrogen can be produced via hydrolysis reaction of chemically active hydrides. Among the metal hydrides, magnesium hydride (MgH2) is considered to be one of the most attractive candidates. However, the hydrolysis reaction is rapidly hindered by the passivation layer formed on the surface of MgH2. In order to improve MgH2 hydrolysis efficiency various approaches have been applied. This paper reviews recent progress on the modifications of MgH2-based materials by adding different type of additives, including metals, oxides, hydroxides, halides and surfactants. The introduced additives possess different catalytic properties due to their intrinsic physical and chemical characteristics, and therefore can strongly influence the hydrolysis reaction of MgH2. The most promising results were obtained for various salt additives showing that the reaction rate depends mostly on the additive type rather than on concentration. The effect of preparation technique on the hydrolysis of MgH2 – MgCl2 composites was studied in detail. The obtained results indicate that efficient hydrolysis performance can be achieved by ball milling of the freshly synthesized MgH2 with 5 wt.% MgCl2 and 1 wt.% TiC–2TiB2 additives. The combination of the applied approaches exhibited a notable synergistic effect on the hydrogen generation.

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CoO-Co2P composite nanosheets as highly active catalysts for sodium borohydride hydrolysis to generate hydrogen

Functional Materials Letters ◽

10.1142/s179360472051025x ◽

2020 ◽

Vol 13 (06) ◽

pp. 2051025

Author(s):

Hongyan Liu ◽

Qianyu Shi ◽

Yumei Yang ◽

Ya-Na Yu ◽

Yan Zhang ◽

...

Keyword(s):

Sodium Borohydride ◽

Hydrogen Generation ◽

Sodium Hypophosphite ◽

X Ray Diffraction ◽

Water Displacement ◽

X Ray ◽

Highly Active ◽

Naoh Solution ◽

Adsorption Desorption ◽

Hydrolysis Of

In this paper, CoO[Formula: see text]Co2P composite nanocatalysts as highly active catalysts were successfully prepared for catalytic hydrolysis of sodium borohydride (NaBH[Formula: see text] to generate hydrogen. For catalyst preparation, pre-synthesized Co(OH)2 nanosheets were uniformly mixed with sodium hypophosphite (NaH2PO[Formula: see text] and then treated through vapor-phase phosphorization process. For characterization, field-emission scanning electron microscopy (FE-SEM), energy dispersive spectrometry (EDS), X-ray diffraction (XRD), N2 adsorption–desorption measurement and X-ray photoelectric spectroscopy (XPS) were carried out, and traditional water-displacement method was performed to measure the hydrogen generation rate (HGR). It was found that component and catalytic activity of the composites were greatly affected by the ratio of Co(OH)2 to NaH2PO2. When the ratio was 2:1, the obtained catalyst composed of CoO and Co2P presented the highest HGR up to 3.94[Formula: see text]L min[Formula: see text] g[Formula: see text] using a 2[Formula: see text]wt.% NaBH[Formula: see text][Formula: see text]wt.% NaOH solution at [Formula: see text]C, and the apparent activation energy was detected as low as 27.4[Formula: see text]kJ mol[Formula: see text]. Additionally, the optimum CoO[Formula: see text]Co2P catalyst still retains 60% of the initial activity after recycling four times.

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Room temperature hydrogen generation from aqueous ammonia-borane using noble metal nano-clusters as highly active catalysts

Journal of Power Sources ◽

10.1016/j.jpowsour.2007.03.015 ◽

2007 ◽

Vol 168 (1) ◽

pp. 135-142 ◽

Cited By ~ 388

Author(s):

Manish Chandra ◽

Qiang Xu

Keyword(s):

Noble Metal ◽

Room Temperature ◽

Hydrogen Generation ◽

Aqueous Ammonia ◽

Ammonia Borane ◽

Highly Active

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Hydrogen Generation From Acetic Acid Catalyzed Magnesium Hydride Using an On-Demand Hydrogen Reactor

Volume 6A: Energy ◽

10.1115/imece2016-66459 ◽

2016 ◽

Cited By ~ 1

Author(s):

Tien-Chien Jen ◽

Joshua Adeniran ◽

Esther Akinlabi ◽

Chung-Hsing Chao ◽

Yen-Hsi Ho ◽

...

Keyword(s):

Acetic Acid ◽

Organic Acid ◽

Hydrogen Generation ◽

Magnesium Hydride ◽

Hydrolysis Reaction ◽

Hydrogen Yield ◽

Acetic Acid Concentration ◽

External Temperature ◽

On Demand ◽

Acid Catalyzed

This study reports an acetic acid catalyzed hydrolysis reaction for hydrogen generation from magnesium hydride (MgH2) using an on-demand hydrogen reactor. Acetic acid, a weak and benign organic acid, has been reported as a single catalyst in hydrolysis reaction for hydrogen generation using other substrates, but this is the first study where acetic acid has been employed as a catalyst in a magnesium hydride hydrolysis reaction for hydrogen generation. In this study, the effects of MgH2 weight, acetic acid concentration and external temperature on hydrogen generation from MgH2 were examined. The results of the hydrolysis reaction indicated that the weight of MgH2 was the major factor influencing hydrogen generation, followed by the concentration of acetic acid while the effect of external temperature was insignificant. Similarly, hydrogen yield was proportional to the weight of MgH2 with a reported maximum hydrogen yield at each weight been: 0.4g (∼ 0.07 L); 0.8 g (∼ 0.125 L) and 1.2 g (∼1.285 L). The successful use of acetic acid in the study reinforced the versatility of the on-demand hydrogen reactor and as a scalable technology for hydrogen generation.

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