• Korean Chemical Engineering Research
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• v.49 no.5
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• pp.516-520
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• 2011

Sodium borohydride, $NaBH_4$, shows a number of advantages as hydrogen source for portable proton exchange membrane fuel cells (PEMFCs). The hydrogen yield of sodium borohydride hydrolysis reaction was studied. The effect of temperature, $NaBH_4$ concentration, NaOH concentration and catalyst type on the hydrogen yield from $NaBH_4$ hydrolysis reaction were measured. The catalysts of Co-P/Cu, Co-B/Cu and Co-P-B/Cu were used in this study and there was no different effect of these catalysts on the hydrogen yield from $NaBH_4$. Under the temperature of $60^{\circ}C$, the hydrogen yield decreased as $NaBH_4$ concentration increased due to formation of gel with by-products and reactants. The gel formed during $NaBH_4$ hydrolysis reaction diminished the hydrogen evolution rate and total volume of hydrogen. Addition of NaOH stabilizer enhanced the formation of gel and then decreased the hydrogen yield.

• Korean Chemical Engineering Research
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• v.57 no.6
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• pp.758-762
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• 2019

Sodium borohydride,$NaBH_4$, has many advantages as hydrogen source for portable proton exchange membrane fuel cells (PEMFC). When PEMFC is used for marine use, $NaBH_4$ hydrolysis using seawater is economical. Therefore, in this study, hydrogen was generated by using seawater instead of distilled water in the process of hydrolysis of $NaBH_4$. Properties of $NaBH_4$ hydrolysis reaction using activated carbon supported Co-B/C catalyst were studied. The yield of hydrogen decreased as $NaBH_4$ concentration and NaOH concentration were increased during $NaBH_4$ hydrolysis using sea water. At higher concentrations of $NaBH_4$ and NaOH, byproducts adhered to the surface of the catalyst after hydrolysis reaction using sea water, reduced hydrogen yield compared to distilled water. The activation energy of $NaBH_4$ hydrolysis is 59.3, 74.4 kJ/mol for distilled water and sea water, respectively. In order to increase the hydrogen generation rate in seawater as high as distilled water, the reaction temperature has to be increased by $80^{\circ}C$ or more.

• Korean Chemical Engineering Research
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• v.59 no.4
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• pp.503-507
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• 2021

Sodium borohydride, NaBH₄, has many advantages as hydrogen source for portable proton exchange membrane fuel cells (PEMFC). When PEMFC is used outdoors as a transport type, it is economical to hydrolyze NaBH₄ using fresh water instead of distilled water. Therefore, in this study, hydrogen was generated using fresh water instead of distilled water during the NaBH₄ hydrolysis process. The properties of NaBH₄ hydrolysis were studied using an activated carbon-supported Co-P-B/C catalyst. Fresh water did not generate tetrahydrate during the NaBH₄ hydrolysis process, and distilled water produced tetrahydrate by-products, which consumed a lot of water during the hydrolysis process, indicating that at the end of the reaction at a high concentration of 25% or more of NaBH₄, dry by-products and unreacted NaBH₄ remained. As a result, when fresh water was used, the hydrogen yield and hydrogen generation rate were higher than that of distilled water at a high concentration of 25% or more of NaBH₄, indicating that it is suitable for use in transport-type fuel cells such as unmanned aerial vehicles.

• Korean Chemical Engineering Research
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• v.54 no.5
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• pp.587-592
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• 2016

Sodium borohydride, $NaBH_4$, shows a number of advantages as hydrogen source for portable proton exchange membrane fuel cells (PEMFCs). Properties of $NaBH_4$ hydrolysis reaction using unsupported Co-P-B Co-B, catalyst at high concentration $NaBH_4$ solution were studied. In order to enhance the hydrogen generation yield at high concentration of $NaBH_4$, the effect of catalyst type, $NaBH_4$ concentration and recovery of condensing water on the hydrogen yield were measured. The yield of hydrogen evolution increased as the boron ratio increased in preparation process of Co-P-B catalyst. The hydrogen yield decreased as the concentration increased from 20 wt% to 25 wt% in $NaBH_4$ solution during hydrolysis reaction using 1:5 Co-P-B catalyst. Maximum hydrogen yield of 96.4% obtained by recovery of condensing water and thinning of catalyst pack thickness in reactor using Co-P-B with Co-B catalyst and 25 wt% $NaBH_4$ solution.

• Korean Chemical Engineering Research
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• v.54 no.1
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• pp.11-15
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• 2016

Proton Exchange Membrane Fuel Cells (PEMFC) instead of batteries is appropriate for long time flight of unmanned aero vehicles (UAV). In this work, $NaBH_4$ hydrolysis system supplying hydrogen to PEMFC was studied. In order to decrease weight of $NaBH_4$ hydrolysis system, enhancement of hydrogen yield, recovery of condensing water and maintenance of stable hydrogen yield were studied. The hydrogen yield of 3.4% was increased by controlling of hydrogen pressure in hydrolysis reactor. Condensing water formed during air cooling of hydrogen was recovered into storage tank of $NaBH_4$ solution. In this process the condensing water dissolved $NaBH_4$ powder and then addition of $NaBH_4$ solution decreased system weight of 14%. $NaBH_4$ hydrolysis system was stably operated with hydrogen yield of 96% by 2.0g Co-P-B catalyst for 10 hours at 2.0L/min hydrogen evolution rate.

• Korean Chemical Engineering Research
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• v.53 no.1
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• pp.11-15
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• 2015

Sodium borohydride, $NaBH_4$, shows a number of advantages as hydrogen source for portable proton exchange membrane fuel cells(PEMFCs). Properties of $NaBH_4$ hydrolysis reaction using unsupported Co-B, Co-P-B catalyst were studied. BET surface area of catalyst, yield of hydrogen, effect of $NaBH_4$ concentration and durability of catalyst were measured. The BET surface area of unsupported Co-B catalyst was $75.7m^2/g$ and this value was 18 times higher than that of FeCrAlloy supported Co-B catalyst. The hydrogen yield of $NaBH_4$ hydrolysis reaction by unsupported catalysts using 20~25 wt% $NaBH_4$ solution was 97.6~98.5% in batch reactor. The hydrogen yield decrease to 95.3~97.0% as the concentration of $NaBH_4$ solution increase to 30 wt%. The loss of unsupported catalyst was less than that of FeCrAlloy supported catalyst during $NaBH_4$ hydrolysis reaction and the loss increased with increasing of $NaBH_4$ concentration. In continuous reactor, hydrogen yield of $NaBH_4$ hydrolysis was 90% using 1.2 g of unsupported Co-P-B catalyst with $3{\ell}/min$ hydrogen generation rate.

• Korean Chemical Engineering Research
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• v.55 no.1
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• pp.13-18
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• 2017

Sodium borohydride, $NaBH_4$, shows a number of advantages as hydrogen source for UAV PEMFC (Unmaned Aerial Vehicle Proton Exchange Membrane Fuel Cells). In order to use for UAV, the weight and volume of byproduct should be small after $NaBH_4$ hydrolysis reaction. Therefore, the weight and volume of byproduct were studied after $NaBH_4$ hydrolysis reaction using unsupported catalyst. The effect of catalyst type, concentration of $NaBH_4$, concentration of NaOH and thickness of catalyst pack on the weight and volume of byproduct were studied. Most of byproduct was $NaB(OH)_4$ and superficial volume of byproduct increased due to foam evolved from byproduct. The weight and volume of byproduct were not affected by concentration of NaOH used stabilizer. The weight of byproduct decreased as concentration of $NaBH_4$ solution increased, but maximum volume of byproduct obtained at 23 wt% of $NaBH_4$. Suitable defoaming agent reduced the volume of byproduct.

• Transactions of the Korean hydrogen and new energy society
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• v.21 no.5
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• pp.383-389
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• 2010

Co-B, Co-P-B, Co-Ni-B and Co-Ni-P-B catalysts supported on Ni foam were prepared using electroless plating in the present study. The surface morphology of the catalysts/Ni foam was observed using SEM and EDS analysis. The Co-Ni-P-B/Ni foam catalyst showed the superior performance on hydrogen generation due to the uniform formation of catalyst particles on the Ni foam surface. The characteristics of hydrogen generation with Co-Ni-P-B/Ni foam catalyst was investigated at the variety of $NaBH_4$ and NaOH concentrations. Durability test was performed, resulting in the stable hydrogen generation for 6 hours.

• Korean Chemical Engineering Research
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• v.50 no.4
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• pp.627-631
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• 2012

Sodium borohydride, $NaBH_4$, shows a number of advantages as hydrogen source for portable proton exchange membrane fuel cells (PEMFCs). The durability of Co-P-B/Cu catalyst for sodium borohydride hydrolysis reaction was studied. The effect of reaction temperature, $NaBH_4$ concentration, NaOH concentration and calcination temperature of catalyst on the durability of Co-P-B/Cu catalyst were measured. The gel formed during hydrolysis reaction affected the durability of catalyst (loss of catalyst). Formation of gel increased the loss of the catalyst. When $NaBH_4$ concentration was high and reaction temperature was higher than $60^{\circ}C$, loss of catalyst was low because gel was not formed. But under the temperature of $40^{\circ}C$, loss of catalyst increased due to gel formation When $NaBH_4$ concentration was 40 weight % and the reaction temperature was $40^{\circ}C$, the loss of catalyst increased as the NaOH concentration increased. As the calcination temperature of catalyst decreased, the loss of catalyst decreased and the activity of catalyst decreased. Calcination of the catalyst at high temperature enhanced the durability of catalyst but diminished the activity of catalyst.

• Korean Chemical Engineering Research
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• v.51 no.1
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• pp.35-41
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• 2013

Properties of $NaBH_4$ hydrolysis reaction using Co-P-B/FeCrAlloy catalyst and the catalyst durability were studied. Co-P-B/FeCrAlloy catalyst showed low activation energy such as 25.2 kJ/mol in 5 wt% $NaBH_4$ solution, which was similar that of noble metal catalyst. The activation energy increased as the $NaBH_4$ concentration increased. Formation of gel at high concentration of $NaBH_4$ seriously affected hydrogen evolution rate and the catalyst durability. The catalyst loss decreased as reaction temperature increased due to lower gel formation when the concentration of $NaBH_4$ was over 20 wt%. Considering hydrogen generation rate and durability of catalyst, the catalyst supported with FeCrAlloy heat-treated at $1,000^{\circ}C$ without ultra vibration during dipping and calcination after catalyst dipping was best catalyst. To use catalyst more than three times in 25 wt% $NaBH_4$ solution, it should be reacted at higher temperature than $60^{\circ}C$.