KINETICS OF HYDROLYSIS OF SODIUM BOROHYDRIDE USING
COBALT CHLORIDE CATALYST
Under guidance of
Pramod K. Bajpai
Dr. D. Gangacharyulu
DEPARTMENT OF CHEMICAL ENGINEERING
Outline of presentation
Results and Discussions
Fossil fuels are depleted at a rate
that is 100,000 times faster than
they are formed.
On average, 16 million tons of
carbon dioxide is emitted into the
atmosphere every 24 hours by
human use worldwide.
Coal is the single biggest air
polluter and burning coal causes
smog, soot, acid rain, global
warming, and toxic air emission.
Transition To Hydrogen Energy
Hydrogen is considered as clean
energy source and long term
1 kg of Hydrogen has same energy
than 2.8 kg of gasoline, therefore
hydrogen stores 2.8 times more
energy than gasoline.
Effective storage of hydrogen is
one of the key elements of
Physical storage in tanks
Compressed Hydrogen Tanks
Cyro-Compressed Hydrogen Storage
Storage in high pressurised tanks up to 700 Hydrogen cooled to 253oC and pressurised
to 6 - 350 bars in insulated tanks.
High energy and cost requirements for Cost factors for cooling and pressurising
pressurising gas in tanks .
hydrogen gas in tanks.
Solid state hydrogen storage
(A) Adsorption, hydrogen attaches to surface of molecules as hydrogen molecules.
Larger quantities of hydrogen in smaller volumes at low pressures and at
temperature nearly equal to room temperature can be stored.
(C) & (D) Hydrogen is strongly bound within molecular structures, as chemical
compounds containing hydrogen atoms.
(B) Absorption, hydrogen molecules dissociate into hydrogen atoms that are
incorporated into the solid lattice framework .
Storing hydrogen in chemical hydrides
H2 Specific mass
(kg H / kg)
(kg H2 / liter)
NaH + H2O → NaOH + H2
CaH2 + 2H2 O → Ca(OH)2 + 2H2
MgH2 → Mg + H2
LiAlH 4 + H2 O → LiOH + Al + 2.5 H2
TiH2 → Ti + H2
LiBH 4 + H2O →
NaBH4 + 2H2O→
LiOH + HBO2 + 4H2
NaBO2 + 4H2
Millennium Cell 35% Solution
NaBH4 + 4H2 O → NaBO2 + 4H2+ 2H2O
Source: M.Klanchar et al. 
Hydride reactions and hydrogen storage
LiH + H2O → LiOH + H2
Comparison of hydrogen storage properties
Source: M. Klanchar et al. 
Sodium borohydride hydrogen storage
NaBH4 + 2H2O
NaBO2 + 4H2
Sodium borohydride reacting with water to produce hydrogen.
Generated H2 is high purity (no traces of CO and S).
It is the least expensive metal hydride commercially available, and it is
safe to use, handle and store.
No side reactions or no volatile by products are formed.
Comparison of chemical hydrides
Source: Y. Wu et al. 
Volumetric storage efficiency
Source: Y. Wu et al. 
Gravimetric storage efficiency
Source: Y. Wu et al. 
CoCl2 + 2NaBH4 + 3H2O
25/4H2 + 1/2Co2B + 2NaCl
Cl- is neoclophilic in nature, Co2+ is electrophlic in nature, which increase its reactivity
toward BH- ions . Therefore this explains better reactivity of CoCl2 for NaBH4.
Source:O.Akdim et al. 
Cobalt chloride as a catalyst for hydrolysis reaction
Hydrogen fraction found best in
LiBH4(0.184), LiH(0.126), LiAlH4
(0.105), NaBH 4 (0.105)
Various modes of
Energy density increases from
compressed hydrogen storage
<cryo- compressed hydrogen
Hydrogen storage system
technologies , role of water in
hydrolysis reaction are discussed
Rate kinetics studied, hydrolysis reaction
with sodium borohydride was found to be
is 1st order.
Hydrogen generation from NaBH4 using Jeong et al.,
Co- B catalyst.
First order kinetics at low NaBH4
concentrations and zero order at high
Cobalt (II) salts
CoCl2 showed best performance in
Best performance was observed by HCl
and CH3COOH followed by citric acid>
oxalic acid>sulphuric acid.
Sodium borohydride (NaBH4) powder with molecular weight of
37.8 g/mol and purity of 97%.
NaOH pellets having molecular weight 39.9 g/mol and purity of
Cobalt chloride (CoCl2) salt powder in hexa-hydrate
form, having molecular weight 237.93 g/mol with a purity of
Schematic diagram of experimental setup
Factors effecting the rate of hydrolysis
According to the hydrolysis reaction at concentration of NaBH4 equal to 0.55
g and CoCl2 concentration 0.06 g, rate of hydrogen generation increases with
increase in temperature.
rate of hydrogen generation (ml/min)
Rate constant with temperature can be expressed by Arrhenius equation
The values of E and A were estimated by substituting the k values at 45 o
C and 63 C, where E = 37.931 kJ/mol and A = 12.54 Χ 108 sec-1.
E is the apparent activation energy, A is the pre exponential factor ,R is
the universal gas constant, and T is the reaction temperature, K.
The Sodium Hydroxide (NaOH) Concentration
NaBH4 undergoes self hydrolysis and to suppress the self hydrolysis
sodium hydroxide (NaOH)is added.
The excess amount of NaOH decreases the hydrogen yield.
Experimental results shows hydrogen generation rate decreases with
increase NaOH concentration and temperature, at constant NaBH4
concentration and CoCl2 concentration.
Rate increase with the increase of NaBH4 concentration at a fixed temperature
and NaOH concentration.
where rH2 is the rate of hydrogen generation in milliliters per minute, mNaBH4 is
the molality of NaBH4, and α is the apparent reaction order, k is proportionality
k 1 w NaOH
where , w NaOH is the concentration of NaOH in weight percent and k1 is a
Hydrogen generation rate decreased with the increase of NaOH concentration
at a fixed NaBH4 concentration and temperature.
Rate law of hydrogen generation from a basic NaBH4 solution can be
expressed using equation ,
1 k 1 w NaOH
Calculated order of the reaction (α) w.r.t NaBH4 concentration equals 1
with experimental error 0.2 and is shown in tabulated form on next slide.
The parameters k/ (1 + k1wNaOH) and α can then be determined by
regressing the maximum hydrogen generation rate and the initial NaBH4
Calculation of the rate constants k and k1
k 1 w NaOH
k m NaBH4
Plot of 1/rH2 versus w NaOH /mNaBH4 gives a straight-line graph.
The intercept on the y axis is 1/kmNaBH4 and the slope is
k1/k, from which both k and k1 may be determined.
Calculations of the rate constants k and k1
Regression at 63oC and 1.45g of NaBH4
Parameters calculated at various temperatures and
Temperature (o C)
Hydrogen Gas Qualitative Analysis by Pop Test
Light a wooden splint and then hold it to area that contain hydrogen, a
squeaky pop is observed if hydrogen is present.
Hydrogen gas quantitative analysis by gas
AIMIL-NUCON Gas Chromatograph
The Test shows the Purity of 85% with rest being nitrogen from air as per
recovery basis from the sample.
A quantitative analysis test was conducted for hydrogen gas by Gas
Chromatography, from Sophisticated Analytical Instrument Laboratory, Thapar
Scanning Electron Microscope (SEM): SEM was performed for the
Laboratory, Thapar University Patiala.
Residue analysis by SEM
2. Energy Dispersive Electron Microscopy (EDAX): EDAX was performed
in Sophisticated Analytical Instrument Laboratory, Thapar University
Patiala. It shows the presence of Sodium (Na), Cobalt (Co), Chlorine
(Cl), Oxygen (O).
Hydrolysis reaction of sodium borohydride with cobalt chloride as catalyst is a
first order reaction.
Hydrogen generation rate increases with increase in temperature, sodium
borohydride (NaBH4) concentration and decreases with sodium hydroxide
The rate constant ‘k’ with respect to sodium borohydride increased significantly
from 555.50 min-1 to 1666.40 min-1 when the temperature increased from 45 to
63 C. However, rate constant ‘k1’ with respect to sodium hydroxide did not
change significantly with NaBH4 concentration and temperature.
The gas chromatography analysis indicates, the hydrogen gas purity is
85% and rest is nitrogen. The tendency of sodium borohydride to store
and release hydrogen is more effective and favorable.
The hydrogen generation rates are observed to be higher from hydrolysis
studies of alumina nanoparticles - NaBH4 - CoCl2 system as compared to
NaBH4 - CoCl2 systems.
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The authors gratefully acknowledge the support provided
by management of Thapar University, Patiala and Thapar
Centre for Industrial Research and Development, Patiala,
India, for providing the necessary facilities to carry out
this research work.