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Review

A Recycling Hydrogen Supply System of NaBH4 Based on a Facile Regeneration Process: A Review

by
Liuzhang Ouyang
1,2,3,
Hao Zhong
1,2,
Hai-Wen Li
4,* and
Min Zhu
1,2,*
1
School of Materials Science and Engineering, Key Laboratory of Advanced Energy Storage Materials of Guangdong Province, South China University of Technology, Guangzhou 510641, China
2
China-Australia Joint Laboratory for Energy & Environmental Materials, South China University of Technology, Guangzhou 510641, China
3
Key Laboratory for Fuel Cell Technology in Guangdong Province, Guangzhou 510641, China
4
Kyushu University Platform of Inter/Transdisciplinary Energy Research, International Research Center for Hydrogen Energy and International Institute for Carbon-Neutral Energy, Kyushu University, Fukuoka 819-0395, Japan
*
Authors to whom correspondence should be addressed.
Inorganics 2018, 6(1), 10; https://doi.org/10.3390/inorganics6010010
Submission received: 24 October 2017 / Revised: 2 January 2018 / Accepted: 5 January 2018 / Published: 6 January 2018
(This article belongs to the Special Issue Functional Materials Based on Metal Hydrides)
Browse Figures
Versions Notes

Abstract

:
NaBH4 hydrolysis can generate pure hydrogen on demand at room temperature, but suffers from the difficult regeneration for practical application. In this work, we overview the state-of-the-art progress on the regeneration of NaBH4 from anhydrous or hydrated NaBO2 that is a byproduct of NaBH4 hydrolysis. The anhydrous NaBO2 can be regenerated effectively by MgH2, whereas the production of MgH2 from Mg requires high temperature to overcome the sluggish hydrogenation kinetics. Compared to that of anhydrous NaBO2, using the direct hydrolysis byproduct of hydrated NaBO2 as the starting material for regeneration exhibits significant advantages, i.e., omission of the high-temperature drying process to produce anhydrous NaBO2 and the water included can react with chemicals like Mg or Mg2Si to provide hydrogen. It is worth emphasizing that NaBH4 could be regenerated by an energy efficient method and a large-scale regeneration system may become possible in the near future.

1. Introduction

Hydrogen [1,2,3] has been widely accepted as a clear energy carrier [4,5,6] due to its high energy density (142 MJ/kg) [7,8,9] and its environmentally friendly byproduct (water) [10,11]. It can be generated via numerous strategies, such as the electrolysis of water [12,13,14] and photocatalytic water splitting [15,16,17,18]. Supplying hydrogen to end users on demand requires safe and efficient methods of hydrogen storage.
Hydrides, storing hydrogen in a safe and compact way without using high pressure, like 70 MPa, or extremely low temperature, like 20 K (liquid hydrogen), have attracted great interest as promising hydrogen storage materials. Though a great deal of progress has been achieved on the development of solid-state hydrogen storage materials in the previous decades, no material with reasonably good hydrogen absorption and desorption performance at near room temperature has been developed to meet all the requirements for onboard hydrogen storage [19,20,21,22,23]. Hydrolysis of hydrides, such as MgH2, ammonia borane (AB), and NaBH4, generating hydrogen with relatively high capacity at room temperature, is attracting increasing interest for hydrogen supply on demand [24,25,26]. Due to the low cost of Mg and the high capacity of MgH2 (7.6 wt %) [27,28,29], much attention has been paid to MgH2 hydrolysis [30,31,32]. However, the reaction is interrupted easily by the formation of a magnesium hydroxide layer [33,34]. Compared with MgH2, AB possesses higher hydrogen capacity (19.6 wt %) [35,36,37]. AB is stable in water and its solubility is as high as 33.6 g/100 mL [38,39], which provides a simple application of AB aqueous solution. Studies have been focused on the development of catalysts to accelerate and control the reaction [40,41,42]. However, the high cost of AB [43] and the difficulty of AB regeneration are major blocks for the application of AB hydrolysis [44,45].
NaBH4 hydrolysis is another promising system for hydrogen generation. It has relatively high hydrogen capacity (10.8 wt %) [46,47,48] and releases hydrogen with high purity at relatively low operational temperature with a controllable process [24,49,50]. Many studies have been focused on the hydrolysis property improvements [51,52,53,54]. Unfortunately, a no-go recommendation on NaBH4 hydrolysis for onboard applications was given by the US Department of Energy (DOE) [55]. One of the key reasons are the cost and the regeneration of NaBH4 [56]. As a result, more focus was shifted into the synthesis and regeneration of NaBH4. For commercial NaBH4 production, the Brown-Schlesinger process [57] and the Bayer process [58] are the most popular methods. The Brown-Schlesinger process produces NaBH4 via the reaction between trimethylborate (B(OCH3)3, TMB) and sodium hydride (NaH), which should be produced by reacting Na and H2. Different from it, the Bayer process is based on the reaction among borax (Na2B4O7), Na, H2, and silicon oxide (SiO2) at 700 °C to synthesize NaBH4. Although the above methods are mature technologies and straightforward procedures, the raw materials are too expensive for NaBH4 hydrolysis applications. Thus, the raw materials have been studied to develop suitable NaBH4 synthesis methods. Instead of Na, MgH2 was used to react with Na2B4O7 to synthesize NaBH4 by ball milling at room temperature. Here, Na2CO3 addition could increase NaBH4 yield up to 78% [59]. This method provides not only a new reducing agent (MgH2) for NaBH4 synthesis, but also a new way of ball milling. Enlightened by it, ball milling became popular in NaBH4 synthesis studies, in which Na and MgH2 reacted with B2O3 by ball milling with the NaBH4 yield of only 25% [60]. When Na was substituted by low-cost NaCl, NaBH4 could also be produced [61]. Later, high-pressure ball milling was also tried to synthesize NaBH4, for instance, NaH was reacted with MgB2 by ball milling under 12 MPa hydrogen pressure with the NaBH4 yield of about 18%.
From the point of cost reduction in synthesis and post-usage of NaBH4, the regeneration of NaBH4 from the byproduct of hydrolysis (see Equation (1) [62]) is in great need for the recycling of the hydrogen supply system of NaBH4:
NaBH4 + xH2O → H2 + NaBO2∙xH2O, (x = 2, 4)
According to this, the Brown-Schlesinger process was modified using NaBO2 as source of boric acid to synthesis of NaBH4 [63], the drawback of which the byproduct NaBO2∙xH2O of hydrolysis needs to be dried first. As another alternative, the electrochemical route was proposed for recycling NaBO2 to NaBH4. Direct electrolysis of a NaBO2 solution was first proven feasible for regeneration of NaBH4 with using palladium (Pd) or platinum (Pt) as electrodes, where the conversion ratio of NaBO2 was about 17% within 48 h [64]. Later, an Ag electrode was also employed in the recycling of NaBO2; unfortunately, the quantities of reborn NaBH4 were too low to be measured [65]. In contrast to the commercial gas-solid methods, the electrochemical method possesses ultra-low efficiency and complex processes, using precious metal electrodes, although the NaBO2 solution that is the main byproduct of NaBH4 hydrolysis can be used directly without dehydration. Therefore, an efficient and simple route is most urgently needed for the cycling of NaBO2 into NaBH4.
In this paper, we discuss the state-of-the-art progress on the regeneration of NaBH4 from anhydrous NaBO2 or the direct byproduct NaBO2∙xH2O. In particular, the regeneration steps and the yield of NaBH4 in each process are summarized in Scheme 1 and the facile regeneration process is also proposed. This review can provide important insights for the recycling hydrogen supply system with high efficiency.

2. NaBH4 Regeneration via the Reaction between Metal or Other Hydrides and NaBO2

As the hydrolysis byproduct of NaBH4, NaBO2 is the main research object of NaBH4 regeneration studies. Many approaches have been adopted to reduce NaBO2 to NaBH4 with different reducing agents. Among the reducing agent, MgH2 is the most effective. Kojima et al. [66] reacted MgH2 with NaBO2 under 550 °C and 7 MPa hydrogen pressure to regenerate NaBH4, and about 97% NaBH4 yield was achieved, while the high reaction temperature and high hydrogen pressure leads to a high energy consumption. Therefore, the thermochemistry method was substituted by room temperature ball milling in this reaction. Hsueh et al. [67], Kong et al. [68] and Çakanyildirim et al. [69] used MgH2 to react with NaBO2 by ball milling under argon. All of their NaBH4 yields were over 70%, which strongly indicated that ball milling is suitable for the reaction between MgH2 and NaBO2. Based on the thermodynamics calculation, we found the maximum energy efficiency of the cycle was 49.91% [70]. Recently, we found that the addition of hydrogen pressure and methanol could further increase the NaBH4 yield by this method [71]. The highest NaBH4 yield could be increased to 89%. In addition to the energy consumption, raw material is another issue that should be considered. Hydrogenation of Mg to produce MgH2 is hard due to its sluggish kinetics, thus resulting in the high cost and high energy consumption in MgH2 production. By modifying the hydrogenation of Mg using Mg-based alloy, the above issue can be partly solved. Following this observation, we tried to use Mg3La hydrides to react with NaBO2 for its advantage of room temperature hydrogenation and low hydrogen purity requirement and found that NaBH4 could be produced (Figure 1a) [70]. However, introduction of other elements influences the regeneration reaction of MgH2. Directly using Mg and H2 in the regeneration may solve the MgH2 production problem. Kojima et al. [66] tried to directly react Mg with NaBO2 under hydrogen, but the yield was extremely low, which may have resulted from the produced MgO obstruction. To promote the yield, Kojima et al. [66] found that Si addition could remarkably increase the NaBH4 yield and Liu et al. [72] found transition metals, like Ni, Fe, and Co, addition could also promote the NaBH4 yield. However, both Si and transition metals keep their own elemental form after the reaction, indicating that such additions would reduce the absolute NaBH4 yield. A pre-milling of the reactants was then found that could also promote the yield. Eom et al. [73] proposed a large-scaled method for reacting Mg with NaBO2 to synthesize NaBH4. After 1 h of ball milling of the reactants, about 69% yield was achieved under 600 °C and 5.5 MPa hydrogen pressure.
For other reducing agents, the Gibbs free energy of the reaction using Ca is much lower than that of Mg. In addition, we found that the energy efficiency of the cycle using Ca is about 43%. For the experiment, Eom et al. tried to substitute Mg by Ca [73], but few NaBH4 was regenerated. Another low cost and abundant metal reductant, Al, was studied by few researchers on NaBH4 regeneration. The only work with respect to Al was reported by Liu et al. [74], expressing that Al could not react with NaBO2 and H2 to produce NaBH4 because of the generated Al2O3. However, if NaBO2 was exchanged to Na4B2O5, the regeneration would succeed at 400 °C and 2.3 MPa pressure of of hydrogen.

3. NaBH4 Regeneration via using NaBO2∙xH2O as Raw Materials

In NaBH4 regeneration, many studies have focused on anhydrous NaBO2 reducing. However, it should be noted that the direct hydrolysis byproduct is hydrated NaBO2. For the NaBH4 aqueous solution hydrolysis, the byproduct is NaBO2∙4H2O [75], while for the solid NaBH4 hydrolysis, the byproduct is NaBO2∙2H2O. Anhydrous NaBO2 should be produced by drying hydrated NaBO2 at 350 °C. If the drying process was omitted, more energy could be saved and the price can be lowered. The energy of the hydrated NaBO2 and anhydrous NaBO2 is shown in Scheme 2. Some studies thus worked on reducing hydrated NaBO2 directly.

3.1. NaBH4 Regeneration via the Reaction between MgH2 and NaBO2∙xH2O

For directly using hydrated NaBO2 as the regeneration raw material, a thermochemistry method was tried. Liu et al. [76] reported that NaBH4 can be regenerated by annealing Mg and NaBO2∙2H2O under hydrogen atmosphere with only 12.3% yield. The low NaBH4 yield may result from the obstruction of the thick generated MgO layer. However, they found that the coordinate water in NaBO2∙2H2O was likely to be the hydrogen source. Considering the generated oxide layer, ball milling might be suitable to break the layer and continue the reaction. Therefore, we tried to used NaBO2∙4H2O or NaBO2∙2H2O to react with MgH2 directly via ball milling to regenerate NaBH4 [77]. NaBH4 was successfully regenerated (Figure 1b):
NaBO2∙2H2O + 4MgH2 → NaBH4 + 4MgO + 4H2
NaBO2∙4H2O + 6MgH2 → NaBH4 + 6MgO + 8H2
The energy efficiency calculated in Section 2 could be improved by approximately 5.2%. Furthermore, a high NaBH4 yield of 89.78% was achieved by this method, which is the highest compared with previous studies [67,69,78].

3.2. NaBH4 Regeneration via the Reaction between Mg and NaBO2∙xH2O

Hydrated NaBO2 could be directly used in NaBH4 regeneration, saving the energy consumption on the dehydration to produce anhydrous NaBO2. However, production of MgH2 from Mg requires high temperature to overcome the sluggish hydrogenation kinetics, resulting in the increased cost. In other words, the energy efficiency could be further promoted and the regeneration cost could be reduced, if the high-temperature hydrogenation process to produce MgH2 can be avoided. According to Liu et al. [76], H in NaBO2∙2H2O could transform to be the H of the regenerated NaBH4. As a result, directly reacting Mg with hydrated NaBO2 was possible to regenerate NaBH4 and avoided the high-temperature hydrogenation process. We found that NaBH4 could be produced by ball milling the NaBO2∙2H2O and Mg mixture under argon (Figure 1c) [79] according to:
NaBO2∙2H2O + 4Mg → NaBH4 + 4MgO
It should be noted that the regenerated H of NaBH4 was completely from the coordinate water. On the other hand, the reaction between NaBO2∙4H2O and Mg could also generate NaBH4 by ball milling:
NaBO2∙4H2O + 6Mg → NaBH4 + 6MgO + H2
Currently, the highest NaBH4 yield of the reaction between Mg and NaBO2∙2H2O is only 68.55%. The energy efficiency needs to be further promoted. Note that the cost of this method is 34-fold lower than the method using MgH2 and NaBO2 in terms of the raw materials required [79].

3.3. NaBH4 Regeneration via the Reaction between Mg2Si and NaBO2∙2H2O

Via ball milling hydrated NaBO2 and Mg, NaBH4 was regenerated and the energy efficiency was further increased. However, the highest NaBH4 yield by this method was 68.55%, which did not reach the general yield of regenerated NaBH4 (~76%) [67,68]. According to Kojima et al. [66], with Si added, the NaBH4 yield was increased in the reaction between NaBO2 and Mg under a hydrogen atmosphere. Therefore, Mg2Si is possible to react with NaBO2∙2H2O to regenerate NaBH4 and improve the NaBH4 yield. We have attempted the above idea in our previous study [80] and found that NaBH4 was regenerated (Figure 1d) according to:
NaBO2∙2H2O + 2Mg2Si → NaBH4 + 4MgO + 2Si
The highest NaBH4 yield was increased to 78% when the Mg2Si and NaBO2∙2H2O mixture was ball milled for 20 h. By using Mg2Si as a reducing agent, the NaBH4 yield was promoted and the H was still from the coordinate water in NaBO2∙2H2O. For the raw materials cost, this method is half of the commercial method and about 30-fold lower than the method using MgH2 and NaBO2 [80].

4. Mechanism of NaBH4 Regeneration Using NaBO2∙xH2O as Raw Materials

The above three works [77,79,80] are new discoveries for direct regeneration of NaBH4 from the hydrated NaBO2 with high yield. Some common points were found in their mechanism studies. In all of the three works, a resonance at approximately −11.4 ppm was observed in the NMR spectra (Figure 2), which belongs to intermediate [BH3(OH)]− [81]. Such an intermediate was likely to generate from [BH(OH)3]− and [BH2(OH)2]−. Conjecturing from the above intermediates, [BH4]− was likely to generate from a step-by-step substitution process of [OH]− in [B(OH)4]− by [H]−. The [H]+ in NaBO2∙xH2O thus transformed to [H]− in this process.
For the reaction between MgH2 and NaBO2∙2H2O, the hydrogen transformation was realized by the substitution of the [OH]− in NaBO2∙xH2O by [H]− in MgH2. For the reaction of Mg and NaBO2∙2H2O, Mg(OH)2 and MgH2 were generated as intermediates and the reactions can be written as:
2MgH2 + NaB(OH)4 → 2Mg(OH)2 + NaBH4
2Mg(OH)2 + 2Mg → 4MgO + 2H2
2H2 + 2Mg → 2MgH2
Since four moles of MgO were generated in this reaction (Equation (4)), it was a strong exergonic reaction. The reaction could be described as a substitution process of [OH]− through the [H]− from the produced intermediate MgH2. During the substitution process, a side reaction may happen. [B3H8]− was generated and then may react with MgH2 and Na+ to form another part of NaBH4 [82]. In the reaction between Mg2Si and NaBO2∙2H2O, Si–H was found (Figure 2d). It was speculated that an intermediate consisting of Mg, O, Si, and H was generated. The [OH]− was transformed to [H]− through a Mg–O–Si–H intermediate. Therefore, though Si was generated with an elemental state after the reaction, Si played an important role in H− formation. Consequently, the substitution process of [OH]− through [H]− was a direct process.
In conclusion, two forms of hydrogen molecules exist in the regeneration. They are H in [OH]− and H in [H]−. When using MgH2 as a reducing agent, H in MgH2 directly substitutes [OH]− in NaB(OH)4. This direct process contributes to the high NaBH4 yield. In the situation of Mg, H in [OH]− first transfer to H in MgH2. Then it substitutes the [OH]− in NaB(OH)4 to form NaBH4. The two-step reaction reduces the NaBH4 yield. For the reaction between Mg2Si and NaBO2∙2H2O, H in [OH]− first transfers to H in Si–H and then it transfers to NaBH4. Although this process is also two steps, the more active Si–H benefits from the higher NaBH4 yield. Therefore, all of the reactions are H transfer processes.

5. Hydrolysis Property of Regenerated NaBH4 Using NaBO2∙xH2O as Raw Materials

Hydrolysis is the main application of the regenerated NaBH4. By the catalysis of CoCl2 [83], NaBH4 could fast hydrolyze with stoichiometry H2O. It was found that the regenerated NaBH4 from NaBO2∙xH2O had an excellent hydrolysis property, which was similar to the commercial NaBH4. According to Figure 3, the highest system hydrogen capacity (containing water and catalyst) was 6.75 wt %, which was the highest compared with previous studies [67,69,78]. It was produced by the reaction between MgH2 and NaBO2∙xH2O. A system hydrogen capacity of 6.33 wt % and 6.3 wt % could also be obtained. Furthermore, the hydrolysis byproduct was indexed to be NaBO2∙2H2O (inset, Figure 3), which was the raw material of our regeneration. As a result, it was demonstrated that a complete cycle of NaBH4 hydrolysis could be achieved by existing works, which was suitable for sustainable application.

6. Summary and Perspective

Application of NaBH4 hydrolysis is limited by its effective regeneration. NaBH4 synthesis and regeneration thus become attractive research topics, especially for the recycling of byproduct NaBO2. For the anhydrous NaBO2 recycling, MgH2 has the best reducing result. However, its high cost, resulting from the high hydrogenation temperature of Mg, limits the application of such methods. For the hydrolysis byproduct hydrated NaBO2, it can also be reduced by MgH2, Mg, or Mg2Si via ball milling, and the highest NaBH4 yield reaches 90%. This process using hydrated NaBO2 exhibits significant advantages, whereby the dehydration process at 350 °C to obtain anhydrous NaBO2 can be omitted and, more importantly, the water included can react with chemicals like Mg and Mg2Si to provide hydrogen instead of using MgH2. As a result, low cost metal (such as Mg, Ca, or Al) becomes possible to be the reducing agent for the NaBH4 regeneration reaction via ball milling, because the [H]+ in the hydrated NaBO2 may directly transform to the [H]− in the hydrated NaBH4. These reactions could operate without extra hydrogen inputs, which provides the possibility of a low-cost and sustainable regeneration. Furthermore, this strategy may also be promoted to other areas, such as LiBH4 production.

Acknowledgments

This work was supported by the Fund for Innovative Research Groups of the National Natural Science Foundation of China (no. NSFC51621001), the National Natural Science Foundation of China Projects (nos. 51431001 and 51771075), and by the Project Supported by Natural Science Foundation of Guangdong Province of China (nos. 2016A030312011 and 2014A030311004). The Project Supported by Guangdong Province Universities and Colleges Pearl River Scholar Funded Scheme (2014) is also acknowledged.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Zhang, X.; Wei, Z.; Guo, Q.; Tian, H. Kinetics of sodium borohydride hydrolysis catalyzed via carbon nanosheets supported Zr/Co. J. Power Sources 2013, 231, 190–196. [Google Scholar] [CrossRef]
  2. Awad, A.S.; El-Asmar, E.; Tayeh, T.; Mauvy, F.; Nakhl, M.; Zakhour, M.; Bobet, J.L. Effect of carbons (G and CFs), TM (Ni, Fe and Al) and oxides (Nb2O5 and V2O5) on hydrogen generation from ball milled Mg-based hydrolysis reaction for fuel cell. Energy 2016, 95, 175–186. [Google Scholar] [CrossRef]
  3. Brack, P.; Dann, S.E.; Wijayantha, K.G.U. Heterogeneous and homogenous catalysts for hydrogen generation by hydrolysis of aqueous sodium borohydride (NaBH4) solutions. Energy Sci. Eng. 2015, 3, 174–188. [Google Scholar] [CrossRef] [Green Version]
  4. Luo, Y.-C.; Liu, Y.-H.; Hung, Y.; Liu, X.-Y.; Mou, C.-Y. Mesoporous silica supported cobalt catalysts for hydrogen generation in hydrolysis of ammonia borane. Int. J. Hydrog. Energy 2013, 38, 7280–7290. [Google Scholar] [CrossRef]
  5. Ding, Q.; Meng, F.; English, C.R.; Cabán-Acevedo, M.; Shearer, M.J.; Liang, D.; Daniel, A.S.; Hamers, R.J.; Jin, S. Efficient photoelectrochemical hydrogen generation using heterostructures of Si and chemically exfoliated metallic MoS2. J. Am. Chem. Soc. 2014, 136, 8504–8507. [Google Scholar] [CrossRef] [PubMed]
  6. Ladomenou, K.; Natali, M.; Iengo, E.; Charalampidis, G.; Scandola, F.; Coutsolelos, A.G. Photochemical hydrogen generation with porphyrin-based systems. Coord. Chem. Rev. 2015, 304, 38–54. [Google Scholar] [CrossRef]
  7. Huang, M.; Ouyang, L.; Wang, H.; Liu, J.; Zhu, M. Hydrogen generation by hydrolysis of MgH2 and enhanced kinetics performance of ammonium chloride introducing. Int. J. Hydrog. Energy 2015, 40, 6145–6150. [Google Scholar] [CrossRef]
  8. Bulut, A.; Yurderi, M.; Ertas, İ.E.; Celebi, M.; Kaya, M.; Zahmakiran, M. Carbon dispersed copper-cobalt alloy nanoparticles: A cost-effective heterogeneous catalyst with exceptional performance in the hydrolytic dehydrogenation of ammonia-borane. Appl. Catal. B 2016, 180, 121–129. [Google Scholar] [CrossRef]
  9. Dudoladov, A.O.; Buryakovskaya, O.A.; Vlaskin, M.S.; Zhuk, A.Z.; Shkolnikov, E.I. Generation of hydrogen by aluminium oxidation in aquaeous solutions at low temperatures. Int. J. Hydrog. Energy 2016, 41, 2230–2237. [Google Scholar] [CrossRef]
  10. Huynh, K.; Napolitano, K.; Wang, R.; Jessop, P.G.; Davis, B.R. Indirect hydrolysis of sodium borohydride: Isolation and crystallographic characterization of methanolysis and hydrolysis by-products. Int. J. Hydrog. Energy 2013, 38, 5775–5782. [Google Scholar] [CrossRef]
  11. Jiang, J.; Materna, K.L.; Hedström, S.; Yang, K.R.; Crabtree, R.H.; Batista, V.S.; Brudvig, G.W. Antimony Complexes for Electrocatalysis: Activity of a Main-Group Element in Proton Reduction. Angew. Chem. Int. Ed. 2017, 56, 9111–9115. [Google Scholar] [CrossRef] [PubMed]
  12. Yilmaz, C.; Kanoglu, M. Thermodynamic evaluation of geothermal energy powered hydrogen production by PEM water electrolysis. Energy 2014, 69, 592–602. [Google Scholar] [CrossRef]
  13. Wang, M.; Wang, Z.; Gong, X.; Guo, Z. The intensification technologies to water electrolysis for hydrogen production—A review. Renew. Sustain. Energy Rev. 2014, 29, 573–588. [Google Scholar] [CrossRef]
  14. Cardoso, D.S.P.; Amaral, L.; Santos, D.M.F.; Šljukić, B.; Sequeira, C.A.C.; Macciò, D.; Saccone, A. Enhancement of hydrogen evolution in alkaline water electrolysis by using nickel-rare earth alloys. Int. J. Hydrog. Energy 2015, 40, 4295–4302. [Google Scholar] [CrossRef]
  15. Kibria, M.G.; Qiao, R.; Yang, W.; Boukahil, I.; Kong, X.; Chowdhury, F.A.; Trudeau, M.L.; Ji, W.; Guo, H.; Himpsel, F.J.; et al. Atomic-Scale Origin of Long-Term Stability and High Performance of p-GaN Nanowire Arrays for Photocatalytic Overall Pure Water Splitting. Adv. Mater. 2016, 28, 8388–8397. [Google Scholar] [CrossRef] [PubMed]
  16. Ma, G.; Chen, S.; Kuang, Y.; Akiyama, S.; Hisatomi, T.; Nakabayashi, M.; Shibata, N.; Katayama, M.; Minegishi, T.; Domen, K. Visible light-driven Z-scheme water splitting using oxysulfide H2 evolution photocatalysts. J. Phys. Chem. Lett. 2016, 7, 3892–3896. [Google Scholar] [CrossRef] [PubMed]
  17. Senthil, V.; Badapanda, T.; Chithambararaj, A.; Chandra Bose, A.; Panigrahi, S. Impedance spectroscopy and photocatalysis water splitting for hydrogen production with cerium modified SrBi2Ta2O9 ferroelectrics. Int. J. Hydrog. Energy 2016, 41, 22856–22865. [Google Scholar] [CrossRef]
  18. Gao, L.; Li, Y.; Ren, J.; Wang, S.; Wang, R.; Fu, G.; Hu, Y. Passivation of defect states in anatase TiO2 hollow spheres with Mg doping: Realizing efficient photocatalytic overall water splitting. Appl. Catal. B 2017, 202, 127–133. [Google Scholar] [CrossRef]
  19. Schlapbach, L.; Zuttel, A. Hydrogen-storage materials for mobile applications. Nature 2001, 414, 353–358. [Google Scholar] [CrossRef] [PubMed]
  20. Principi, G.; Agresti, F.; Maddalena, A.; Lo Russo, S. The problem of solid state hydrogen storage. Energy 2009, 34, 2087–2091. [Google Scholar] [CrossRef]
  21. Sakintuna, B.; Lamari-Darkrim, F.; Hirscher, M. Metal hydride materials for solid hydrogen storage: A review. Int. J. Hydrog. Energy 2007, 32, 1121–1140. [Google Scholar] [CrossRef]
  22. Lim, K.L.; Kazemian, H.; Yaakob, Z.; Daud, W.R.W. Solid-state Materials and Methods for Hydrogen Storage: A Critical Review. Chem. Eng. Technol. 2010, 33, 213–226. [Google Scholar] [CrossRef]
  23. Khafidz, N.Z.A.K.; Yaakob, Z.; Lim, K.L.; Timmiati, S.N. The kinetics of lightweight solid-state hydrogen storage materials: A review. Int. J. Hydrog. Energy 2016, 41, 13131–13151. [Google Scholar] [CrossRef]
  24. Amendola, S.C.; Sharp-Goldman, S.L.; Janjua, M.S.; Kelly, M.T.; Petillo, P.J.; Binder, M. An ultrasafe hydrogen generator: Aqueous, alkaline borohydride solutions and Ru catalyst. J. Power Sources 2000, 85, 186–189. [Google Scholar] [CrossRef]
  25. Cao, N.; Hu, K.; Luo, W.; Cheng, G. RuCu nanoparticles supported on graphene: A highly efficient catalyst for hydrolysis of ammonia borane. J. Alloys Compd. 2014, 590, 241–246. [Google Scholar] [CrossRef]
  26. Ouyang, L.Z.; Dong, H.W.; Peng, C.H.; Sun, L.X.; Zhu, M. A new type of Mg-based metal hydride with promising hydrogen storage properties. Int. J. Hydrog. Energy 2007, 32, 3929–3935. [Google Scholar] [CrossRef]
  27. Liu, Y.; Du, H.; Zhang, X.; Yang, Y.; Gao, M.; Pan, H. Superior catalytic activity derived from a two-dimensional Ti3C2 precursor towards the hydrogen storage reaction of magnesium hydride. Chem. Commun. 2016, 52, 705–708. [Google Scholar] [CrossRef] [PubMed]
  28. Ouyang, L.Z.; Cao, Z.J.; Wang, H.; Liu, J.W.; Sun, D.L.; Zhang, Q.A.; Zhu, M. Enhanced dehydriding thermodynamics and kinetics in Mg(In)–MgF2 composite directly synthesized by plasma milling. J. Alloys Compd. 2014, 586, 113–117. [Google Scholar] [CrossRef]
  29. Ouyang, L.Z.; Huang, J.M.; Fang, C.J.; Zhang, Q.A.; Sun, D.L.; Zhu, M. The controllable hydrolysis rate for LaMg12 hydride. Int. J. Hydrog. Energy 2012, 37, 12358–12364. [Google Scholar] [CrossRef]
  30. Ouyang, L.; Ma, M.; Huang, M.; Duan, R.; Wang, H.; Sun, L.; Zhu, M. Enhanced Hydrogen Generation Properties of MgH2-Based Hydrides by Breaking the Magnesium Hydroxide Passivation Layer. Energies 2015, 8, 4237–4252. [Google Scholar] [CrossRef]
  31. Varin, R.A.; Jang, M.; Czujko, T.; Wronski, Z.S. The effect of ball milling under hydrogen and argon on the desorption properties of MgH2 covered with a layer of Mg(OH)2. J. Alloys Compd. 2010, 493, L29–L32. [Google Scholar] [CrossRef]
  32. Kadri, A.; Jia, Y.; Chen, Z.; Yao, X. Catalytically Enhanced Hydrogen Sorption in Mg-MgH2 by Coupling Vanadium-Based Catalyst and Carbon Nanotubes. Materials 2015, 8, 3491–3507. [Google Scholar] [CrossRef]
  33. Hiraki, T.; Hiroi, S.; Akashi, T.; Okinaka, N.; Akiyama, T. Chemical equilibrium analysis for hydrolysis of magnesium hydride to generate hydrogen. Int. J. Hydrog. Energy 2012, 37, 12114–12119. [Google Scholar] [CrossRef]
  34. Tayeh, T.; Awad, A.S.; Nakhl, M.; Zakhour, M.; Silvain, J.F.; Bobet, J.L. Production of hydrogen from magnesium hydrides hydrolysis. Int. J. Hydrog. Energy 2014, 39, 3109–3117. [Google Scholar] [CrossRef]
  35. Fernandes, R.; Patel, N.; Paris, A.; Calliari, L.; Miotello, A. Improved H2 production rate by hydrolysis of Ammonia Borane using quaternary alloy catalysts. Int. J. Hydrog. Energy 2013, 38, 3313–3322. [Google Scholar] [CrossRef]
  36. Kantürk Figen, A.; Coşkuner, B. A novel perspective for hydrogen generation from ammonia borane (NH3BH3) with Co–B catalysts: “Ultrasonic Hydrolysis”. Int. J. Hydrog. Energy 2013, 38, 2824–2835. [Google Scholar] [CrossRef]
  37. Rakap, M. PVP-stabilized Ru–Rh nanoparticles as highly efficient catalysts for hydrogen generation from hydrolysis of ammonia borane. J. Alloys Compd. 2015, 649, 1025–1030. [Google Scholar] [CrossRef]
  38. Yang, X.J.; Li, L.L.; Sang, W.L.; Zhao, J.L.; Wang, X.X.; Yu, C.; Zhang, X.H.; Tang, C.C. Boron nitride supported Ni nanoparticles as catalysts for hydrogen generation from hydrolysis of ammonia borane. J. Alloys Compd. 2017, 693, 642–649. [Google Scholar] [CrossRef]
  39. Durak, H.; Gulcan, M.; Zahmakiran, M.; Ozkar, S.; Kaya, M. Hydroxyapatite-nanosphere supported ruthenium(0) nanoparticle catalyst for hydrogen generation from ammonia-borane solution: Kinetic studies for nanoparticle formation and hydrogen evolution. Rsc. Adv. 2014, 4, 28947–28955. [Google Scholar] [CrossRef]
  40. Garralda, M.A.; Mendicute-Fierro, C.; Rodriguez-Dieguez, A.; Seco, J.M.; Ubide, C.; Zumeta, I. Efficient hydridoirida-beta-diketone-catalyzed hydrolysis of ammonia- or amine-boranes for hydrogen generation in air. Dalton Trans. 2013, 42, 11652–11660. [Google Scholar] [CrossRef] [PubMed]
  41. Barakat, N.A.M. Catalytic and photo hydrolysis of ammonia borane complex using Pd-doped Co nanofibers. Appl. Catal. A 2013, 451, 21–27. [Google Scholar] [CrossRef]
  42. Jiang, H.-L.; Xu, Q. Catalytic hydrolysis of ammonia borane for chemical hydrogen storage. Catal. Today 2011, 170, 56–63. [Google Scholar] [CrossRef]
  43. Li, H.; Yang, Q.; Chen, X.; Shore, S.G. Ammonia borane, past as prolog. J. Organomet. Chem. 2014, 751, 60–66. [Google Scholar] [CrossRef]
  44. Summerscales, O.T.; Gordon, J.C. Regeneration of ammonia borane from spent fuel materials. Dalton Trans. 2013, 42, 10075–10084. [Google Scholar] [CrossRef] [PubMed]
  45. Sutton, A.D.; Davis, B.L.; Bhattacharyya, K.X.; Ellis, B.D.; Gordon, J.C.; Power, P.P. Recycle of tin thiolate compounds relevant to ammonia-borane regeneration. Chem. Commun. 2010, 46, 148–149. [Google Scholar] [CrossRef] [PubMed]
  46. Zhou, Y.; Fang, C.; Fang, Y.; Zhu, F.; Liu, H.; Ge, H. Hydrogen generation mechanism of spontaneous hydrolysis: A sight from ab initio calculation. Int. J. Hydrog. Energy 2016, 41, 22668–22676. [Google Scholar] [CrossRef]
  47. Retnamma, R.; Novais, A.Q.; Rangel, C.M. Kinetics of hydrolysis of sodium borohydride for hydrogen production in fuel cell applications: A review. Int. J. Hydrog. Energy 2011, 36, 9772–9790. [Google Scholar] [CrossRef]
  48. Zhong, H.; Wang, H.; Liu, J.W.; Sun, D.L.; Fang, F.; Zhang, Q.A.; Ouyang, L.Z.; Zhu, M. Enhanced hydrolysis properties and energy efficiency of MgH2-base hydrides. J. Alloys Compd. 2016, 680, 419–426. [Google Scholar] [CrossRef]
  49. Nunes, H.X.; Ferreira, M.J.F.; Rangel, C.M.; Pinto, A.M.F.R. Hydrogen generation and storage by aqueous sodium borohydride (NaBH4) hydrolysis for small portable fuel cells (H2 – PEMFC). Int. J. Hydrog. Energy 2016, 41, 15426–15432. [Google Scholar] [CrossRef]
  50. Chinnappan, A.; Puguan, J.M.C.; Chung, W.-J.; Kim, H. Hydrogen generation from the hydrolysis of sodium borohydride using chemically modified multiwalled carbon nanotubes with pyridinium based ionic liquid and decorated with highly dispersed Mn nanoparticles. J. Power Sources 2015, 293, 429–436. [Google Scholar] [CrossRef]
  51. Lin, K.-Y.A.; Chang, H.-A. Efficient hydrogen production from NaBH4 hydrolysis catalyzed by a magnetic cobalt/carbon composite derived from a zeolitic imidazolate framework. Chem. Eng. J. 2016, 296, 243–251. [Google Scholar] [CrossRef]
  52. Demirci, U.B.; Miele, P. Cobalt in NaBH4 hydrolysis. Phys. Chem. Chem. Phys. 2010, 12, 14651–14665. [Google Scholar] [CrossRef] [PubMed]
  53. Zhu, J.; Li, R.; Niu, W.; Wu, Y.; Gou, X. Fast hydrogen generation from NaBH4 hydrolysis catalyzed by carbon aerogels supported cobalt nanoparticles. Int. J. Hydrog. Energy 2013, 38, 10864–10870. [Google Scholar] [CrossRef]
  54. Wang, M.C.; Ouyang, L.Z.; Liu, J.W.; Wang, H.; Zhu, M. Hydrogen generation from sodium borohydride hydrolysis accelerated by zinc chloride without catalyst: A kinetic study. J. Alloys Compd. 2017, 717, 48–54. [Google Scholar] [CrossRef]
  55. Program, U.S.D.o.E.H. Go/No-Go Recommendation for Sodium Borohydride for On-Board Vehicular Hydrogen Storage. Available online: http://www.hydrogen.energy.gov/pdfs/42220.pdf (accessed on 1 July 2017).
  56. Demirci, U.B.; Akdim, O.; Miele, P. Ten-year efforts and a no-go recommendation for sodium borohydride for on-board automotive hydrogen storage. Int. J. Hydrog. Energy 2009, 34, 2638–2645. [Google Scholar] [CrossRef]
  57. Schlesinger, H.I.; Brown, H.C.; Finholt, A.E. The Preparation of Sodium Borohydride by the High Temperature Reaction of Sodium Hydride with Borate Esters1. J. Am. Chem. Soc. 1953, 75, 205–209. [Google Scholar] [CrossRef]
  58. Johnson, W.C.; Isenberg, S. Hydrogen Compounds of Silicon. I. The Preparation of Mono- and Disilane. J. Am. Chem. Soc. 1935, 57, 1349–1353. [Google Scholar] [CrossRef]
  59. Li, Z.P.; Morigazaki, N.; Liu, B.H.; Suda, S. Preparation of sodium borohydride by the reaction of MgH2 with dehydrated borax through ball milling at room temperature. J. Alloys Compd. 2003, 349, 232–236. [Google Scholar] [CrossRef]
  60. Çakanyildirim, Ç.; Gürü, M. The Production of NaBH4 from Its Elements by Mechano-chemical Reaction and Usage in Hydrogen Recycle. Energy Sources Part A 2011, 33, 1912–1920. [Google Scholar] [CrossRef]
  61. Bilen, M.; Gürü, M.; Çakanyıldırım, Ç. Role of NaCl in NaBH4 production and its hydrolysis. Energ Convers. Manag. 2013, 72, 134–140. [Google Scholar] [CrossRef]
  62. Marrero-Alfonso, E.Y.; Gray, J.R.; Davis, T.A.; Matthews, M.A. Minimizing water utilization in hydrolysis of sodium borohydride: The role of sodium metaborate hydrates. Int. J. Hydrog. Energy 2007, 32, 4723–4730. [Google Scholar] [CrossRef]
  63. Ved, A.S.; Miley, G.H.; Seetaraman, T.S. Recycling Sodium Metaborate to Sodium Borohydride Using Wind-Solar Energy System for Direct Borohydride Fuel Cell. In Proceedings of the ASME 2010 8th International Fuel Cell Science, Engineering and Technology, Brooklyn, NY, USA, 14–16 June 2010; pp. 139–141. [Google Scholar]
  64. Sanli, A.E.; Kayacan, İ.; Uysal, B.Z.; Aksu, M.L. Recovery of borohydride from metaborate solution using a silver catalyst for application of direct rechargable borohydride/peroxide fuel cells. J. Power Sources 2010, 195, 2604–2607. [Google Scholar] [CrossRef]
  65. McLafferty, J.; Colominas, S.; Macdonald, D.D. Attempts to cathodically reduce boron oxides to borohydride in aqueous solution. Electrochim. Acta 2010, 56, 108–114. [Google Scholar] [CrossRef]
  66. Kojima, Y.; Haga, T. Recycling process of sodium metaborate to sodium borohydride. Int. J. Hydrog. Energy 2003, 28, 989–993. [Google Scholar] [CrossRef]
  67. Hsueh, C.-L.; Liu, C.-H.; Chen, B.-H.; Chen, C.-Y.; Kuo, Y.-C.; Hwang, K.-J.; Ku, J.-R. Regeneration of spent-NaBH4 back to NaBH4 by using high-energy ball milling. Int. J. Hydrog. Energy 2009, 34, 1717–1725. [Google Scholar] [CrossRef]
  68. Kong, L.; Cui, X.; Jin, H.; Wu, J.; Du, H.; Xiong, T. Mechanochemical Synthesis of Sodium Borohydride by Recycling Sodium Metaborate. Energy Fuels 2009, 23, 5049–5054. [Google Scholar] [CrossRef]
  69. Çakanyıldırım, Ç.; Gürü, M. Processing of NaBH4 from NaBO2 with MgH2 by ball milling and usage as hydrogen carrier. Renew. Energy 2010, 35, 1895–1899. [Google Scholar] [CrossRef]
  70. Ouyang, L.Z.; Zhong, H.; Li, Z.M.; Cao, Z.J.; Wang, H.; Liu, J.W.; Zhu, X.K.; Zhu, M. Low-cost method for sodium borohydride regeneration and the energy efficiency of its hydrolysis and regeneration process. J. Power Sources 2014, 269, 768–772. [Google Scholar] [CrossRef]
  71. Lang, C.; Jia, Y.; Liu, J.; Wang, H.; Ouyang, L.; Zhu, M.; Yao, X. NaBH4 regeneration from NaBO2 by high-energy ball milling and its plausible mechanism. Int. J. Hydrog. Energy 2017, 42, 13127–13135. [Google Scholar] [CrossRef]
  72. Liu, B. Kinetic characteristics of sodium borohydride formation when sodium meta-borate reacts with magnesium and hydrogen. Int. J. Hydrog. Energy 2008, 33, 1323–1328. [Google Scholar] [CrossRef]
  73. Eom, K.; Cho, E.; Kim, M.; Oh, S.; Nam, S.-W.; Kwon, H. Thermochemical production of sodium borohydride from sodium metaborate in a scaled-up reactor. Int. J. Hydrog. Energy 2013, 38, 2804–2809. [Google Scholar] [CrossRef]
  74. Liu, B.H.; Li, Z.P.; Zhu, J.K.; Morigasaki, N.; Suda, S. Sodium Borohydride Synthesis by Reaction of Na2O Contained Sodium Borate with Al and Hydrogen. Energy Fuels 2007, 21, 1707–1711. [Google Scholar] [CrossRef]
  75. Beaird, A.M.; Li, P.; Marsh, H.S.; Al-Saidi, W.A.; Johnson, J.K.; Matthews, M.A.; Williams, C.T. Thermal Dehydration and Vibrational Spectra of Hydrated Sodium Metaborates. Ind. Eng. Chem. Res. 2011, 50, 7746–7752. [Google Scholar] [CrossRef]
  76. Liu, B.H.; Li, Z.P.; Zhu, J.K. Sodium borohydride formation when Mg reacts with hydrous sodium borates under hydrogen. J. Alloys Compd. 2009, 476, L16–L20. [Google Scholar] [CrossRef]
  77. Chen, W.; Ouyang, L.Z.; Liu, J.W.; Yao, X.D.; Wang, H.; Liu, Z.W.; Zhu, M. Hydrolysis and regeneration of sodium borohydride (NaBH4)—A combination of hydrogen production and storage. J. Power Sources 2017, 359, 400–407. [Google Scholar] [CrossRef]
  78. Zhang, H.; Zheng, S.; Fang, F.; Chen, G.; Sang, G.; Sun, D. Synthesis of NaBH4 based on a solid-state reaction under Ar atmosphere. J. Alloys Compd. 2009, 484, 352–355. [Google Scholar] [CrossRef]
  79. Ouyang, L.; Chen, W.; Liu, J.; Felderhoff, M.; Wang, H.; Zhu, M. Enhancing the Regeneration Process of Consumed NaBH4 for Hydrogen Storage. Adv. Energy Mater. 2017, 7, 1700299. [Google Scholar] [CrossRef]
  80. Zhong, H.; Ouyang, L.Z.; Ye, J.S.; Liu, J.W.; Wang, H.; Yao, X.D.; Zhu, M. An one-step approach towards hydrogen production and storage through regeneration of NaBH4. Energy Storage Mater. 2017, 7, 222–228. [Google Scholar] [CrossRef]
  81. Andrieux, J.; Demirci, U.B.; Hannauer, J.; Gervais, C.; Goutaudier, C.; Miele, P. Spontaneous hydrolysis of sodium borohydride in harsh conditions. Int. J. Hydrog. Energy 2011, 36, 224–233. [Google Scholar] [CrossRef]
  82. Chong, M.; Karkamkar, A.; Autrey, T.; Orimo, S.-I.; Jalisatgi, S.; Jensen, C.M. Reversible dehydrogenation of magnesium borohydride to magnesium triborane in the solid state under moderate conditions. Chem. Commun. 2011, 47, 1330–1332. [Google Scholar] [CrossRef] [PubMed]
  83. Dai, H.-B.; Ma, G.-L.; Kang, X.-D.; Wang, P. Hydrogen generation from coupling reactions of sodium borohydride and aluminum powder with aqueous solution of cobalt chloride. Catal. Today 2011, 170, 50–55. [Google Scholar] [CrossRef]
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Scheme 1. Flowchart of (a) NaBH4 regeneration via the reaction between MgH2 and NaBO2. (b) NaBH4 regeneration via the reaction between MgH2 and NaBO2∙xH2O. (c) NaBH4 regeneration via the reaction between Mg and NaBO2∙xH2O. (d) NaBH4 regeneration via the reaction between Mg2Si and NaBO2∙2H2O. Numbers indicate the yield of NaBH4.
Scheme 1. Flowchart of (a) NaBH4 regeneration via the reaction between MgH2 and NaBO2. (b) NaBH4 regeneration via the reaction between MgH2 and NaBO2∙xH2O. (c) NaBH4 regeneration via the reaction between Mg and NaBO2∙xH2O. (d) NaBH4 regeneration via the reaction between Mg2Si and NaBO2∙2H2O. Numbers indicate the yield of NaBH4.
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Scheme 2. Schematic energy diagram of the boron material for the recycling of NaBO2 to NaBH4, NaBO2∙2H2O to NaBH4, and NaBO2∙4H2O to NaBH4.
Scheme 2. Schematic energy diagram of the boron material for the recycling of NaBO2 to NaBH4, NaBO2∙2H2O to NaBH4, and NaBO2∙4H2O to NaBH4.
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Figure 1. (a) XRD patterns of the NaBO2–Mg3La hydride mixture and the product after ball milling the NaBO2–Mg3La hydride mixture. (b) XRD pattern of products via ball-milling the mixture of NaBO2∙2H2O and MgH2 in 1:5.5 mol ratio for 15 h. (c) XRD pattern of products via ball-milling the mixture of NaBO2·2H2O and Mg in 1:5 mole ratio for 15 h. (d) XRD patterns of the products after ball milling Mg2Si and NaBO2∙2H2O mixtures (in 2:1 mol ratio).
Figure 1. (a) XRD patterns of the NaBO2–Mg3La hydride mixture and the product after ball milling the NaBO2–Mg3La hydride mixture. (b) XRD pattern of products via ball-milling the mixture of NaBO2∙2H2O and MgH2 in 1:5.5 mol ratio for 15 h. (c) XRD pattern of products via ball-milling the mixture of NaBO2·2H2O and Mg in 1:5 mole ratio for 15 h. (d) XRD patterns of the products after ball milling Mg2Si and NaBO2∙2H2O mixtures (in 2:1 mol ratio).
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Figure 2. (a) Solid-state 11B NMR spectra of products after ball milling MgH2 and NaBO2∙2H2O mixtures (in 5.0:1 mol ratio). (b) Solid-state 11B NMR spectra of products after ball milling Mg and NaBO2·2H2O mixtures (in 5.0:1 mole ratio). (c) 11B MAS NMR spectra of the products after ball milling Mg2Si and NaBO2∙2H2O mixtures (in 2:1 mol ratio). (d) FT-IR spectra of the products after ball milling Mg2Si and NaBO2∙2H2O mixtures (in 2:1 mol ratio).
Figure 2. (a) Solid-state 11B NMR spectra of products after ball milling MgH2 and NaBO2∙2H2O mixtures (in 5.0:1 mol ratio). (b) Solid-state 11B NMR spectra of products after ball milling Mg and NaBO2·2H2O mixtures (in 5.0:1 mole ratio). (c) 11B MAS NMR spectra of the products after ball milling Mg2Si and NaBO2∙2H2O mixtures (in 2:1 mol ratio). (d) FT-IR spectra of the products after ball milling Mg2Si and NaBO2∙2H2O mixtures (in 2:1 mol ratio).
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Figure 3. Hydrolysis curves of (a) the regeneration product (MgH2 and NaBO2∙xH2O). (b) The regeneration product (Mg and NaBO2∙xH2O). (c) The purified product (Mg2Si and NaBO2∙2H2O) and the commercial NaBH4 in 5 wt % CoCl2 aqueous solution. Inset: XRD patterns of (a) a standard PDF card of NaBO2·2H2O and (b) the hydrolysis byproduct.
Figure 3. Hydrolysis curves of (a) the regeneration product (MgH2 and NaBO2∙xH2O). (b) The regeneration product (Mg and NaBO2∙xH2O). (c) The purified product (Mg2Si and NaBO2∙2H2O) and the commercial NaBH4 in 5 wt % CoCl2 aqueous solution. Inset: XRD patterns of (a) a standard PDF card of NaBO2·2H2O and (b) the hydrolysis byproduct.
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Ouyang, L.; Zhong, H.; Li, H.-W.; Zhu, M. A Recycling Hydrogen Supply System of NaBH4 Based on a Facile Regeneration Process: A Review. Inorganics 2018, 6, 10. https://doi.org/10.3390/inorganics6010010

AMA Style

Ouyang L, Zhong H, Li H-W, Zhu M. A Recycling Hydrogen Supply System of NaBH4 Based on a Facile Regeneration Process: A Review. Inorganics. 2018; 6(1):10. https://doi.org/10.3390/inorganics6010010

Chicago/Turabian Style

Ouyang, Liuzhang, Hao Zhong, Hai-Wen Li, and Min Zhu. 2018. "A Recycling Hydrogen Supply System of NaBH4 Based on a Facile Regeneration Process: A Review" Inorganics 6, no. 1: 10. https://doi.org/10.3390/inorganics6010010

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