Synthesis of Co2B nanostructures and their catalytic properties for hydrogen generation

Yıl 2017, Cilt: 2 Sayı: 1, 28 - 36, 16.03.2017

Tuncay Şimşek Mustafa Barış

Öz

Pure cobalt
(II) boride nanoparticles/nanocylinders were synthesized in aqueous media under
Argon blanket using cobalt chloride (CoCl₂) and sodium borohydride (NaBH₄)
as reactants. CoCl₂ (0.325 g) was
dissolved in cold distilled water (DDI) and the solution was introduced into a
sealed glass reactor. Then, NaBH₄ was then dissolved in DDI (90 mL)
and the solution was added drop-wise into the reactor and stirred magnetically
at 300 rpm. By the addition of NaBH₄ (10 mL, 0.225 g) solution,
amorphous black cobalt boride particles were synthesized
immediately.  The presence of crystalline Co₂B phase with high purity in
the nanocylinders which is obtained by calcination at 500^oC was shown by X-ray
diffraction spectroscopy. An amorphous Co₂B structure was observed with the sample dried under
vacuum. In the synthesis runs, Co₂B nanoparticles with different morphological
characteristics were achieved by changing the initial CoCl₂
concentration and the reaction period. A microscopic structure in the form of nanocylinders
was observed for the calcined products. The nanocylinder diameter increased
from ca. 30 nm to 100 nm by increasing the reaction time from 3 to 120 min.
CoCl₂ initial concentration was also found another factor increasing
the nanocylinder diameter. The nanocylinders with diameters between 80-500 nm were
obtained by increasing CoCl₂ concentration from 12.6 to 100.1
mM. The lowest and highest saturation
magnetization values were obtained 19 and 69 emu/g for crystalline sample
calcined under air (Co-Co₂B mixture) and amorphous Co₂B sample
obtained by vacuum-drying, respectively. Amorphous and crystalline Co₂B
samples were used as catalyst for Hydrogen generation by the hydrolysis of NaBH₄
in aqueous media. Amorphous Co₂B gave significantly higher H₂
generation rate with respect to the catalysts prepared by calcination of
amorphous Co₂B under air or Argon at 500^oC.  The maximum H₂ generation rate was
obtained as 1.1 L/g catalyst.min by using amorphous Co₂B with
1 % w/w of initial NaBH₄ concentration. 

Anahtar Kelimeler

Cobalt boride, H2 generation, sodium borohydride, hydrolysis, cobalt oxide

Kaynakça

• Akdim A., Demirci U., Muller D., Miele P., Cobalt (II) salts, performing materials for generating hydrogen from sodium borohydride, Int. J. Hydrogen Energy, 34, 2631-2637, 2009.
• Zhao J., Ma H., Chen J., Improved hydrogen generation from alkaline NaBH4 solution using carbon-supported Co-B as catalysts, Int. J. Hydrogen Energy, 32, 4711-4716, 2007.
• Ye W., Zhang H., Xu D., Ma L., Yi B., Hydrogen generation utilizing alkaline sodium borohydride solution and supported cobalt catalyst, J. Power Sources, 164, 544-548, 2007.
• Xu D., Dai P., Liu X., Cao C., Guo Q., Carbon-supported cobalt catalyst for hydrogen generation from alkaline sodium borohydride solution, J. Power Sources, 182, 616-620, 2008.
• Lin S. S. Y., Kim D. H., Ha S. Y., Hydrogen production from ethanol steam reforming over supported cobalt catalysts, Catal. Lett., 122, 295-301, 2008.
• Dai H. B., Liang Y., Wang P., Yao X., Rufford T., Lu M., Cheng H., High-performance cobalt–tungsten–boron catalyst supported on Ni foam for hydrogen generation from alkaline sodium borohydride solution, Int. J. Hydrogen Energy, 33, 4405-4412, 2008.
• Hung T. F., Kuo H. C., Tsai C. W., Chen H. M., Liu R. S., Bing-Jhih Weng B. J., Lee J. F., An alternative cobalt oxide-supported platinum catalyst for efficient hydrolysis of sodium borohydride, J. Mater. Chem., 21, 11754-11759. 2011.
• Shubhanwita S., Abhirup B., Debnath D., Saibal G., Dipali B., Kajari K., Novel graphene supported Co rich connected core(Pt)-shell(Co) nano-alloy catalyst for improved hydrogen generation and electro-oxidation, Int. J. Hydrogen Energy, 41, (41), 18451–18464, 2016.
• Yuyao H., Kunyang W., Liang C., Wenxin Z., Abdullah M. A., Xuping S., Effective hydrolysis of sodium borohydride driven by self-supported cobalt oxide nanorod array for on-demand hydrogen generation, Catal. Commun., 87, 94–97, 2016.
• Netskina O. V., Komova O. V., Simagina V. I., Odegova G.V., Prosvirin I. P., Bulavchenko O. A., Aqueous-alkaline NaBH4 solution: The influence of storage duration of solutions on reduction and activity of cobalt catalysts, Renewable Energy, 99, 1073–1081, 2016.