Sodium Borohydride

Hydrogen generation by the catalyzed NaBH4 :
"Just add water"

Catalyzed sodium borohydride reacts with water to generate large amounts of hydrogen, according to the following reaction:

NaBH4 + 4 H2O   ⇒  4 H2 + NaB(OH)4

This reaction approaches a remarkable 20 % gravimetric efficiency when calculated in relation to the weight of the NaBH4alone, and in excess of 6 wt.% when calculated in relation to both water and NaBH4.

However the reaction requires a catalyst. Without the catalyst, sodium borohydride dissolves in water without noticeable hydrogen generation. With inadequate catalysts, on the other hand, the reaction results in the hydrated forms of borax, which significantly decreases the overall gravimetric efficiency and increases the cost and energy input in the regeneration process.

The formation of sodium borohydroxide is crucial for the efficient NaBH4 hydrolysis.

 Otherwise, excess of water is necessary and solubility problems arise, which result in the formation of the hydrated complexes.

 

Hydrogen generator with the catalytic hydrolysis of sodium borohydride

This ia an ideal hydrogen source for fuel cell demonstrations and anaerobic experiments. No need for high hydrogen pressures and unnecessary hydrogen accumulation,

 

Performance of our catalyst is shown in the following video.

The catalyst performs rapidly both in the solution flow conditions (using a water solution of NaBH4), as well as in the “just add water” conditions of solid sodium borohydride being used for the hydrogen generation. The amount of 1-3 wt.% of the catalyst is sufficient to complete the decomposition of NaBH4 within several minutes to up to one hour (or longer if needed). The generation of hydrogen is highly controllable through the used amount of the catalyst and the amount of water. 

The catalyst is in the form of a powder that can be handled and stored in air without deterioration. It is made of common and very inexpensive metals, without any noble metals or harmful components, making it both easy to recover and/or expendable. The reaction product is a fully transformed solid sodium borohydroxide, as shown below.

         

Final reaction product - complete hydrolysis with no water left

The amount of added water can be as little as 2:1 by weight (water to NaBH4), giving in practice the weight percentage of generated H2 in excess of 6 wt.% (calculated in relation to both water and NaBH4). When related to the weight of the dry NaBH4 to be carried in the storage cartridge – the gravimetric efficiency of the hydrogen generation reaches 20 wt%. The addition of about as little as 1% of the catalyst powder to the NaBH4gives vigorous and steady generation of hydrogen until the completion of the hydrolysis reaction.

The small setup (0.3g of NaBH4 + 10 mg of the catalyst + 0.6g of tap water) generates hydrogen flow of excess of 20 ml/min. Larger amounts of NaBH4 generate proportionally larger flow rates of hydrogen. Much higher flow can be generated with increased amounts of the catalyst. The process is scalable up to hydrogen flowrate of the order of tens of  liters per minute.

Features of the catalytic generation of hydrogen:

  • Control over the reaction through the amount of the catalyst added and through either successive or stepwise addition of water
  • No excess of water is needed above the reaction stoichiometry
  • The catalyst is cheap and contains only common components – no noble metals at all.
  • The catalyst can be stored in air without deterioration. It requires no activation or any treatment before use.

 

     


Please contact us with inquires related  to purchase of our hydrogen generators, catalysts or catalyzed materials at contact@hydrogenlink.com

 


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