Hydrogen storage properties of various carbon supported NaBH₄ prepared via metathesis

Yang, Heena,Lombardo, Loris,Luo, Wen,Kim, Whajung,Zü,ttel, Andreas Elsevier 2018 International journal of hydrogen energy Vol.43 No.14

<P><B>Abstract</B></P> <P>Sodium borohydride nanoparticles prepared via the metathesis reaction between LiBH<SUB>4</SUB> and NaCl were successfully deposited on various carbon supporting materials such as graphite, graphene oxide and carbon nanotubes. The X-ray diffraction analyses were conducted to identify the phase of NaBH<SUB>4</SUB> deposited on various carbon supporting materials. The transmittance electron micrograph analyses were also conducted to investigate the particle size and dispersion of NaBH<SUB>4</SUB> within carbon supporting materials. The particle size and size distribution of NaBH<SUB>4</SUB> on graphite were observed to be larger and broader than of other two supporting materials, graphene oxide and CNT due to the lower surface energy as compared to GO and CNT. The bonding state of NaBH<SUB>4</SUB> was confirmed by the Fourier-transformed infrared spectroscopy analysis. The TG and PCT results show that the hydrogen desorption of the NaBH<SUB>4</SUB> deposited on carbon supports takes place at temperature (130 °C∼) significantly lower than that of pure NaBH<SUB>4</SUB> (above 500 °C) and the amount of desorption was in the order of graphene oxide (12.3 mass %) > CNT (9.8 mass %) > graphite (5.7 mass %). The reversibility of hydrogen adsorption after five cycles of adsorption-desorption showed that NaBH<SUB>4</SUB>/GO and NaBH<SUB>4</SUB>/CNT were much better than that of pure NaBH<SUB>4</SUB> due to excellent structural stability.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Borohydrides nanoparticles show a faster sorption rate at lower temperatures. </LI> <LI> NaBH4 nanoparticles were formed in range of 3–6 nm by the metathesis reaction. </LI> <LI> The nanoparticle size of NaBH4 shows the hydrogen desorption starting at 130 °C. </LI> <LI> NaBH4 particles with carbon support desorbed up to 12.3 mass% of hydrogen. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Schematic diagram of preparing NaBH<SUB>4</SUB> with various carbon materials.</P> <P>[DISPLAY OMISSION]</P>

Membrane electrode assembly fabricated with the combination of Pt/C and hollow shell structured-Pt-SiO₂@ZrO₂ sphere for self-humidifying proton exchange membrane fuel cell

Ko, Y.D.,Yang, H.N.,Zü,ttel, Andreas,Kim, S.D.,Kim, W.J. Elsevier 2017 Journal of Power Sources Vol.367 No.-

<P><B>Abstract</B></P> <P>The Pt-supported hollow structured Pt-HZrO<SUB>2</SUB> with the shell thickness of 27 nm is successfully synthesized. The water retention ability of Pt-HZrO<SUB>2</SUB> is significantly enhanced compared with that of SiO<SUB>2</SUB>@ZrO<SUB>2</SUB> due to the hydrophilic hollow structured HZrO<SUB>2</SUB>with high BET surface area. Pt-C and Pt-HZrO<SUB>2</SUB> are combined with different weight fractions to prepare the double catalyst electrode (DCE). The membrane electrode assembly with the DCE is fabricated and applied to both anode and cathode or anode side only. The water flooding and thus rapid voltage drop is affected by the presence/or absence of the DCE at the cathode side. The cell test and visual experiment suggests that the Pt-HZrO<SUB>2</SUB> layer adsorb the water molecules generated by the oxygen reduction reaction (ORR), preventing the water flooding. The power generation under RH 0% strongly suggests the back-diffusion of water molecules generated by the ORR. The flow rate to the cathode significantly affects the water flooding and cell performance. Higher flow rate to the cathode is advantageous to expel the water generated by the ORR, thus preventing water flooding and enhancing the cell performance. Therefore, the weight fraction of Pt-C to Pt-HZrO<SUB>2</SUB> and the flow rate to the cathode should be well balanced.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Hollow shell structured Pt-HZrO<SUB>2</SUB> is combined with Pt-C for self-humidifying PEMFC. </LI> <LI> The water retention ability is highly enhanced compared with that of SiO<SUB>2</SUB>@ZrO<SUB>2</SUB>. </LI> <LI> Pt-HZrO<SUB>2</SUB> layer at cathode side is essential for the prevention of water flooding. </LI> <LI> Flow rate to the cathode is critical in the aspect of preventing water flooding. </LI> <LI> Pt/C to Pt-HZrO<SUB>2</SUB> ratio and the flow rate to the cathode should be well balanced. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

학동 접단 요검사의 임상적 의의

진복희 ( Bok Hee Jin ),김정화 ( Jung Hwa Kim ),박살뜰 ( Sal Ttel Park ) 대한임상검사과학회 2000 대한임상검사과학회지(KJCLS) Vol.32 No.3

In order to investigate the urine examinations for children who hand had kiφley and the urinary tract diseases, we examined protein, occult blood, and glucose in urine of 3,123 children (1652 male, 52.9% and 1,471 female, 47.1 %) who go to 10 elementary schools in Iksan City, from Mrach to Jtme, 1999.We fotmd that 13.6% of children demonstrated positive reactions to at least one of the urine examinations(1.31 % of protein test, 12.23% of occult blood test and 0.06% of glucose test) and that less than 0.29% of children have positive reactions of protein, and above 1 + of occult bl00d, together.We did microscopical observations for red blood cel(RBC) cotmts. πley show that the number of RBC is not increased in urine with positive reaction of protein, but increased in urine with positive reaction of occult blood. These resu1ts indicate that children’s group urine examinations were useful in discovering and surveying patienst with or without self-consciousness of kidney and or urinary tract diseases.

Pressure and temperature dependence of the decomposition pathway of LiBH₄

Yan, Yigang,Remhof, Arndt,Hwang, Son-Jong,Li, Hai-Wen,Mauron, Philippe,Orimo, Shin-ichi,Zü,ttel, Andreas The Royal Society of Chemistry 2012 Physical chemistry chemical physics Vol.14 No.18

<P>The decomposition pathway is crucial for the applicability of LiBH<SUB>4</SUB> as a hydrogen storage material. We discuss and compare the different decomposition pathways of LiBH<SUB>4</SUB> according to the thermodynamic parameters and show the experimental ways to realize them. Two pathways, <I>i.e.</I> the direct decomposition into boron and the decomposition <I>via</I> Li<SUB>2</SUB>B<SUB>12</SUB>H<SUB>12</SUB>, were realized under appropriate conditions, respectively. By applying a H<SUB>2</SUB> pressure of 50 bar at 873 K or 10 bar at 700 K, LiBH<SUB>4</SUB> is forced to decompose into Li<SUB>2</SUB>B<SUB>12</SUB>H<SUB>12</SUB>. In a lower pressure range of 0.1 to 10 bar at 873 K and 800 K, the concurrence of both decomposition pathways is observed. Raman spectroscopy and <SUP>11</SUP>B MAS NMR measurements confirm the formation of an intermediate Li<SUB>2</SUB>B<SUB>12</SUB>H<SUB>12</SUB> phase (mostly Li<SUB>2</SUB>B<SUB>12</SUB>H<SUB>12</SUB> adducts, such as dimers or trimers) and amorphous boron.</P> <P>Graphic Abstract</P><P>The thermodynamic properties of LiBH<SUB>4</SUB> and its possible decomposition products and intermediates allow flexibility in selection of the decomposition pathway by tuning the external parameters such as pressure and temperature. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2cp40131b'> </P>

The effect of Al on the hydrogen sorption mechanism of LiBH₄

Friedrichs, O.,Kim, J. W.,Remhof, A.,Buchter, F.,Borgschulte, A.,Wallacher, D.,Cho, Y. W.,Fichtner, M.,Oh, K. H.,Zü,ttel, A. Royal Society of Chemistry 2009 Physical chemistry chemical physics Vol.11 No.10

<P>We demonstrate the synthesis of LiBH<SUB>4</SUB> from LiH and AlB<SUB>2</SUB> without the use of additional additives or catalysts at 450 °C under hydrogen pressure of 13 bar to the following equation: 2LiH + AlB<SUB>2</SUB> + 3H<SUB>2</SUB>↔ 2LiBH<SUB>4</SUB> + Al. By applying AlB<SUB>2</SUB> the kinetics of the formation of LiBH<SUB>4</SUB> is strongly enhanced compared to the formation from elemental boron. The formation of LiBH<SUB>4</SUB> during absorption requires the dissociation of AlB<SUB>2</SUB>, <I>i.e.</I> a coupled reaction. The observed low absorption-pressure of 13 bar, measured during hydrogen cycling, is explained by a low stability of AlB<SUB>2</SUB>, in good agreement with theoretical values. Thus starting from AlB<SUB>2</SUB> instead of B has a rather low impact on the thermodynamics, and the effect of AlB<SUB>2</SUB> on the formation of LiBH<SUB>4</SUB> is of kinetic nature facilitating the absorption by overcoming the chemical inertness of B. For desorption, the decomposition of LiBH<SUB>4</SUB> is not indispensably coupled to the immediate formation of AlB<SUB>2</SUB>. LiBH<SUB>4</SUB> may decompose first into LiH and elemental B and during a slower second step AlB<SUB>2</SUB> is formed. In this case, no destabilization will be observed for desorption. However, due to similar stabilities of LiBH<SUB>4</SUB> and LiBH<SUB>4</SUB>/Al a definite answer on the desorption mechanism cannot be given and neither a coupled nor decoupled desorption can be excluded. At low hydrogen pressures the reaction of LiH and Al gives LiAl under release of hydrogen. The formation of LiAl increases the total hydrogen storage capacity, since it also contributes to the LiBH<SUB>4</SUB> formation in the absorption process.</P> <P> </P> <P>Graphic Abstract</P><P>LiBH<SUB>4</SUB> (LiBD<SUB>4</SUB>) is synthesized by hydrogenation of LiH (LiD) and AlB<SUB>2</SUB> without use of additional additives or catalysts. The reversible reaction mechanism is investigated. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b814282c'> </P>