Hydrogen energy in changing environmental scenario: Indian context

i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 3 4 ( 2 0 0 9 ) 7 3 5 8 – 7 3 6 7

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Hydrogen energy in changing environmental scenario:Indian context

M. Sterlin Leo Hudson, P.K. Dubey, D. Pukazhselvan, Sunil Kumar Pandey, Rajesh KumarSingh, Himanshu Raghubanshi, Rohit. R. Shahi, O.N. Srivastava*

Hydrogen Energy Center, Department of Physics, Banaras Hindu University, Varanasi 221005, Uttar Pradesh, India

a r t i c l e i n f o

Article history:

Received 30 July 2008

Received in revised form

25 May 2009

Accepted 25 May 2009

Available online 25 June 2009

Keywords:

Climate change

Nanostructured TiO2

Hydrogen production rate

Modular PEC solar cells

Intermetallic hydrides

Complex hydrides

Hydrogen fueled vehicles

* Corresponding author. Tel.: þ91 542 236846E-mail address: [email protected] (O.N

0360-3199/$ – see front matter ª 2009 Interndoi:10.1016/j.ijhydene.2009.05.107

a b s t r a c t

This paper deals with how the Hydrogen Energy may play a crucial role in taking care of the

environmental scenario/climate change. The R&D efforts, at the Hydrogen Energy Center,

Banaras Hindu University have been described and discussed to elucidate that hydrogen is

the best option for taking care of the environmental/climate changes. All three important

ingredients for hydrogen economy, i.e., production, storage and application of hydrogen

have been dealt with. As regards hydrogen production, solar routes consisting of photo-

electrochemical electrolysis of water have been described and discussed. Nanostructured

TiO2 films used as photoanodes have been synthesized through hydrolysis of

Ti[OCH(CH3)2]4. Modular designs of TiO2 photoelectrode-based PEC cells have been fabri-

cated to get high hydrogen production rate (w10.35 lh�1 m�2). However, hydrogen storage

is a key issue in the success and realization of hydrogen technology and economy. Metal

hydrides are the promising candidates due to their safety advantage with high volume

efficient storage capacity for on-board applications. As regards storage, we have discussed

the storage of hydrogen in intermetallics as well as lightweight complex hydride systems.

For intermetallic systems, we have dealt with material tailoring of LaNi5 through Fe

substitution. The La(Nil � xFex)5 (x¼ 0.16) has been found to yield a high storage capacity of

w2.40 wt%. We have also discussed how CNT admixing helps to improve the hydrogen

desorption rate of NaAlH4. CNT (8 mol%) admixed NaAlH4 is found to be optimum for faster

desorption (w3.3 wt% H2 within 2 h). From an applications point of view, we have focused

on the use of hydrogen (stored in intermetallic La–Ni–Fe system) as fuel for Internal

Combustion (IC) engine-based vehicular transport, particularly two and three-wheelers. It

is shown that hydrogen used as a fuel is the most effective alternative fuel for circum-

venting climate change.

ª 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights

reserved.

1. Introduction (pollution free), renewable and environmentally friendly. The

The emission of green house gases, particularly, CO2 from

industries and automobile exhaust makes serious impact on

the climate [1–4]. Unlike petroleum fuels, hydrogen is clean

8; fax: þ91 542 2368889.. Srivastava).ational Association for H

Hydrogen energy is the only renewable energy which can

provide clean commercial energies, the electricity and the fuel

for transport. Cold combustion of hydrogen in fuel cell leads to

the creation of electrical power and hot combustion in

ydrogen Energy. Published by Elsevier Ltd. All rights reserved.

mailto:[email protected]

http://www.elsevier.com/locate/he

i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 3 4 ( 2 0 0 9 ) 7 3 5 8 – 7 3 6 7 7359

internal combustion (IC) engines of motor vehicles provides

power in the same way as fossil fuel does. Both the cold and

hot combustion processes lead to production of water.

Hydrogen can be produced through a variety of processes by

dissociation of water. Thus, produced from water, hydrogen

burns back to water. It is indigenous and unlike petroleum

which has to be imported, hydrogen can be produced within

the country. The main advantage of hydrogen as a fuel is the

absence of CO2 emissions [2]. Hydrogen is considered as

a renewable and sustainable solution for reducing global fossil

fuel consumption and combating global warming [3].

Hydrogen is of paramount relevance for countries like India.

Some important reasons for this are outlined in the following.

(a) India has only 0.9% of world oil reserves (as against 5% for

China; 15% for USA and 59% for the Middle East). India will

always be fuel starved if it depends on oil alone. Thus,

hydrogen which can replace oil, will relieve us from this

burden.

(b) India is currently importing about 122 MT of oil per year.

Hence, we have to pay a huge amount in foreign exchange

to oil exporting countries (mostly the Middle East coun-

tries). The increase by merely 1US$ of price in the inter-

national market leads to an additional burden on India

worth Rupees 3000 crores. This is a very big burden on

India’s economy. Hydrogen will relieve this burden.

(c) Environmental/climate change has become possibly the

most important reason to switch over to hydrogen. Global

warming will affect the whole world, but India will be one of

the countries which will suffer most. This is evident from

the illuminating Stern Report, which was released in

October 2006 [1]. The Stern Report, among its other virtues,

quantifies the effect of climate change economically. It

appears that India is already losing about 1% of GNP due to

climate change. As per IPCC Report (C/o Dr. R.K. Pachauri)

published in 2007 [4], in India change in temperature is

observed to be 0.68 �C increase per century. Several cata-

strophic changes are already occurring in India. Thus, for

example as the report points out because of climate change

effects, 944 mm of rainfall occurred in Mumbai (India) on

26–27 July 2005, killing 1000 people and loss of property

worth US$250 million. It thus appears that even if oil may

still be present, it may not be used as a fuel in view of the

climate change, crucial calamities which it will lead to.

We will now discuss how the hydrogen economy can be

realized. For this, three main steps, i.e., production, storage

and application will have to be accomplished. In the following,

we will proceed to describe and discuss these with special

reference to R&D efforts at the Hydrogen Energy Center (HEC),

Banaras Hindu University (BHU), Varanasi. A detail of such

R&D has also been given in one of our earlier publication [5].

However, the results reported here are different.

2. Photoelectrochemical electrolysis route ofhydrogen production

The hydrogen production routes can be categorized under solar

and non-solar routes. Hydrogen can be produced by employing

solar energy through two prominent ways: (a) Photovoltaic (PV)

driven electrolysis of water; (b) photoelectrochemical (PEC)

electrolysis of water. The former is a compound process using

first PV electricity generation and then electrolysis. Even though

it is a feasible process, efficiencies will be limited. The efficien-

cies of the single-crystalline silicon PV cells at maximum power

point have been found to be w15.4% under testing conditions

of 1000 W/m2 solar irradiation, ambient temperature and

156.25 cm2 cell area [6]. The latter method, PEC electrolysis, is

a single step process; the dissociation of H2O is done by elec-

trons and holes produced in the semiconducting photo-

electrode upon illumination with solar light. Fujishima and

Honda [7] first reported in 1972 the experiment of water elec-

trolysis using solar energy as the sole driving force for water

decomposition. Breakthrough R&D efforts by Bockris et al. [8,9]

and Gerischer [10,11] established the scientific foundations of

photoelectrochemical hydrogen generation.

According to Veziroglu [12,13], the method of photo-

electrochemical water decomposition using solar energy is

the most promising method for the generation of hydrogen.

This view has been supported by a recent comprehensive

review on hydrogen generation [14]. The urgent need to

develop hydrogen technologies has resulted in much R&D

activity on materials for solar hydrogen [15–19]. The PEC solar

cells can be improved by the use of novel materials to increase

the conversion efficiency of solar energy into chemical energy

[20–25]. R&D on solar hydrogen production through the pho-

toelectrochemical (PEC) route employing a suitable semi-

conductor as the photoanode is of considerable interest.

3. Hydrogen production at HEC-BHU,employing PEC electrolysis

3.1. Investigation and optimization of photoelectrodearea employing nanostructured TiO2-based PEC solar cellsfor hydrogen production through photoelectrochemicalprocess

The developments concerning particularly nanostructured

(e.g. TiO2) photoelectrodes have received much attention,

because of their very high effective surface area and high

incident photon-to-current conversion efficiency [21]. It is

necessary to estimate the optimum photoelectrode geometric

area in order to investigate photoelectrochemical solar cells

with modular configuration which might lead to a ‘hydrogen

production reactor’. We shall now look at these issues and

determine the optimum photoelectrode area and then fabri-

cation of the modular PEC solar cells for efficient electrical/

hydrogen production. The nanostructured TiO2 (ns-TiO2) films

have been prepared through a sol–gel route employing

Ti[OCH(CH3)2]4 and carrying out hydrolysis. The chemical

process can be represented as:

Ti�OCHðCH3Þ2

�4

/Hydrolysis

80�CTiO2ðsol-gelÞ

Details of the preparation and characterization of nano-

structured TiO2 and fabrications of PEC solar cells based on

these electrodes have been described in detail in our earlier

papers [25–28].


The following is a general description of the experiments

and conclusions.

(i) The nanostructured TiO2 films were prepared through

sol–gel technique followed by their deposition over Ti-

conducting substrate [26].

(ii) The structural characterization revealed that the depos-

ited TiO2 film corresponds to the anatase phase (tetrag-

onal: a¼ 3.785 A and c¼ 9.514 A) with some peaks from

the rutile phase (tetragonal: a¼ 4.593 A and c¼ 2.959 A)

and Ti substrate and the microstructural feature revealed

a fine-grained network of nanoparticles, suggesting the

formation of nanocrystalline film with average grain size

w2 nm. The selected area electron diffraction pattern

confirmed the formation of nano-sized anatase crystal-

lites [27].

(iii) Based on the studies on the optimization of the effective

photoelectrode area, it has been found that the optimum

TiO2 photoelectrode area for adequate photoconversion

efficiency and hydrogen production rate corresponds to

w0.50 cm2 [27].

(iv) From PV-biased PEC cell experiments, it is possible to

have a PV-assisted photoelectrochemical water electrol-

ysis which may be beneficial over dark PV powered water

electrolysis, since only a small biasing potential is needed

for water electrolysis. Further, such a water electrolysis

system represents an all-solar powered device.

Fig. 1 – Schematic representation of parallel-connected

photoelectrodes in modular PEC cell.

3.2. Nanostructured TiO2-based PEC solar cells forhydrogen production

To obtain improved efficiencies and hydrogen production

rates, it is necessary to develop suitable photoelectrodes.

These should be such that loss of photogenerated carriers is at

its lowest. There is a need to design modular cell systems,

which can lead not only to improved response and efficiency

but can also reduce the cost and complexity of the photo-

electrochemical cells systems. Keeping these aspects in view,

we have taken three different configurations: (i) a single cell;

(ii) parallel-connected cells; and (iii) a cell with the electrode

area equivalent to the area of combined cells. For the parallel

combination, two and four cells with larger and smaller area

were combined. The photoconversion efficiencies of the cells

(single cell, parallel combined cells and a cell with the elec-

trode area equivalent to the area of combined cells) have been

determined and compared for both the configurations [28].

3.2.1. Physical arrangement of the PEC solar cellsThe PEC solar cells were fabricated using nanostructured TiO2

photoelectrodes. The nanostructured TiO2 photoelectrodes so

prepared were fixed over separate perspex mounts having

a central hole of predefined area using a chemically inert epoxy

resin. Perspex mounts were used in the rectangular PEC cell.

Alkaline water has been used as electrolyte and as the source of

hydrogen. It is in direct contact with nanostructured TiO2

photoelectrodes film (not flowing). To achieve PV-assisted

photoelectrochemical water electrolysis, the potential was

applied through an external PV panel (with output from w1.0 to

5.0 V) between the working and reference electrode, keeping

reference and counter electrodes shorted together. The elec-

trodes are electrically connected in a parallel manner; not with

respect to water flow, because the water is not flowing.

3.2.1.1. Photo-electrochemical characterization. The variation

of the photocurrent density (Jp) as a function of measured

potential (Emeas) versus saturated calomel electrode (SCE) for

the PEC solar cells with the electrode area, viz. 0.40 cm2 and its

different combinations have been measured. The photocur-

rent density for module cells has also been recorded. It was

found that the photocurrent density for a PEC cell with pho-

toelectrode area 1.85 cm2 is 1.50 mAcm�2 at w0.40 V versus

SCE and on doubling the photoelectrode area (i.e. 3.70 cm2) its

value decreases to w1.08 mAcm�2 [28]. The value of photo-

current density for the PEC cells with photoelectrode area

0.40 cm2 and 1.60 cm2 at �0.52 V versus SCE corresponds to

2.77 mAcm�2 and 1.75 mAcm�2, respectively. It was found

that the decrease in the photocurrent density is only 3% for

the modular cell with area (4� 0.40 cm2) [28]. Upon illumina-

tion (energy of the incident photon being more than the band

gap of TiO2), electrons and holes are produced in the

conduction and valance band of the semiconductor. Here, in

the case of parallel-connected cells, overall photocurrents

would be additives of individual cells (as they are electrically

connected to each other through the Ti substrate). It is

expected that if the area of the photoelectrode is smaller, the

defects and hence recombination centers for electrons and

holes will be smaller leading to higher photocurrent; and vice

versa for large area photoelectrodes. From these observations,

it is evident that the photocurrent density decreases rapidly

on increasing the photoelectrode area which is due to increase

in the defect states originating mostly from grain boundaries/

surface defects acting as the recombination center. In contrast

to this, the slight decrease in the photocurrent density in the

case of modular cells may be related to the shadow effect at

the edges of the finger mask, or to the decrease in photon

density in light beam used for the illumination on moving

outwards from the center of the photoelectrode. Thus, it

would be beneficial to fabricate the modular PEC cell with

smaller area electrodes connected in parallel.

3.2.1.2. Photoconversion efficiency. Fig. 1 shows the schematic

diagram of parallel-connected photoelectrodes in the modular


PEC cell. The maximum photoconversion efficiency was found

to be 2.52% for the PEC cell with photoelectrode area 0.40 cm2.

However, the maximum photoconversion efficiency, for a PEC

cell with a relatively small photoelectrode area as well as for

a modular cell made of smaller photoelectrodes, corresponds

to a lower applied potential (viz., Eapp¼ 0.45 V) in comparison to

the PEC cells and modular cell made of relatively large photo-

electrodes (where h max corresponds to Eapp¼ 0.57 V) [28].

3.2.1.3. Hydrogen production measurements. The hydrogen

production rate was determined for an applied bias Eapp cor-

responding to maximum in photoconversion efficiency

for both types of cells. The rates of hydrogen production for

a single cell with photoelectrode area 3.70 cm2 and for

a module (2� 1.85 cm2) have been found to be 4.15 lh�1 m�2

and 5.31 lh�1 m�2, respectively. Similarly, for the case of a PEC

cell with photoanode area 1.6 cm2 and a modular cell

(4� 0.4 cm2), the measured values of hydrogen production

rate correspond to 6.72 lh�1 m�2 and 10.35 lh�1 m�2, respec-

tively. This is shown in Fig. 2. Thus, in the former case, the

hydrogen production rate increases only by 27% on using

a modular cell of the same effective area. On the other hand,

for the module with individual electrodes of relatively smaller

area (i.e. for 4� 0.4 cm2 module) the hydrogen production rate

increases by 54%. Therefore, the hydrogen production rate can

be improved by employing modular PEC cells in the form of

Fig. 2 – Hydrogen production rate from single cell

(area [ 0.40 cm2) and modular cell (area [ 4 3 0.40 cm2).

Table 1 – Area of electrodes, photocurrent density and photoco

SL. No. Type of the cell Area of theelectrodes (cm2)

Photodensity

1. Single Cell 0.40 2

1.60 1

1.85 1

3.70 1

2. Modular cell 4� 0.40¼ 1.60 2

2� 1.85¼ 3.70 1

parallel-connected photoelectrodes of smaller area. The

variations of different PEC parameters for the fabricated

modular PEC solar cells are given in Table 1.

4. Hydrogen storage

Storage is a key issue for the hydrogen economy. It cuts across

the production, distribution, safety and applications aspects

[29–31]. One gram of hydrogen gas occupies w11 L (2.9 gallons)

of space at STP, so storage implies a need to reduce the

enormous volume occupied by hydrogen. All the practical

storage options have disadvantages, but still, the most

promising appears to be hydrides. A viable means of hydrogen

storage excludes inefficient and risky high-pressure cylinders,

expensive cryogenic cylinders and all covalent hydrocarbon

compounds.

The solution to these obstacles appears to be storage of

hydrogen in the form of hydrides. A hydrogen storage alloy

is capable of absorbing and releasing hydrogen without

compromising its own structure. Hydrogen storage in metal

hydrides is considered to be a potential storage method and

has attracted considerable interest [30,31].

4.1. Intermetallic hydrides

Hydrides hold promise for safe mode of hydrogen storage. The

BHU group has widely investigated hydrides of intermetallic

compounds as typified by AB, AB5, AB2 and A2B for the last two

decades. ‘A’ corresponds to the binary hydride forming tran-

sition element and ‘B’ is arbitrarily any transition element.

Some key materials which have been investigated by BHU

group in the last 10 years are given in Table 2. The interme-

tallic hydrides can be able to meet the volumetric storage

efficiency of w60 Kg/m3, required for vehicular applications.

However, decades of extensive research on traditional inter-

metallic hydrides have led to achieve only a moderate

increase in gravimetric storage efficiency, not sufficient for

vehicular applications. One alternative option to improve the

hydrogen storage capacity is by partial substitution of another

element, having higher electron attractive power [32]. Thus,

for and AB5 type intermetallic system (e.g. LaNi5), one such

feasible substitution would correspond to partial replacement

of Ni by Fe or Co or both. This is evident by their electronic

configurations as in the following:

Ni..3d84s2;Co..3d74s2;Fe..3d64s2

nversion efficiency of the modular cells.

current(mAcm�2)

Photoconversionefficiency (%)

Hydrogen productionrate (L/hm2)

.77 2.52 6.72

.75 1.63 –

.50 1.17 4.15

.08 0.85 –

.69 2.45 10.35

.38 1.07 5.31

Table 2 – Key materials investigated by BHU group in the last 10 years.

AB TiFe, TiFe0.9Mn0.1, TiFe0.8Ni0.2,

AB5 LaNi5, MmNi5, MmNi4.15Al0.85, MmNi4.5Al0.5, MmNi4.6Fe0.4, La(Nil � x � yFexSiy)5, MmNi4.3Al0.3Mn0.4,

La0.2Mm0.8Ni3.7Al0.48Co0.3Mn0.5Mo0.02, La0.2Mm0.75Ti0.05Ni3.7Al0.48Co0.3Mn0.5Mo0.02

AB2 ZrFe2, TiCr2, TiV0.6Fe0.15Mn1.25, FeTi1 � xMmx, Zr(Fe1 � xCrx)2 0� x� 0.4, Zr1 � 2xMnxTixFe1.4Cr0.6 (x¼ 0.0, 0.1, 0.2, 0.05)

A2B Mg2Ni, Mg2Fe, Mg2Cu

Composites La2Mg17, La2Mg17–x wt% LaNi5, Mg–x wt% FeTi, Mg–x wt% CFMNi5, LaNi5/La2Ni7, Mg–x wt% MmNi4.6Fe0.4 etc.


Hydrogen absorption would increase if the substituting

atom has the capacity to attract this electron (H atom). Thus,

more H atoms can be incorporated (absorbed) and the storage

capacity will increase. Since both Fe and Co have more

vacancies in the 3d shell than the parent Ni atom, their

substitution is likely to increase the hydrogen storage

capacity. Another element which has higher electron attrac-

tive power than Ni (.3d84s2) is V (.3d34s2). Similar consid-

erations may apply for the other metallic ingredient, that is, La

in LaNi5. The La corresponds to 5d16s2 and Ce to 4f15d16s2.

Thus, partial substitution of Ce for La may enhance the

storage capacity (it should be pointed out that the concen-

trations of the substituting atoms have to be found out

through a series of substitutions for determining the optimum

hydrogen storage material which possesses the highest

reversible hydrogen storage capacity). One example of our

efforts in this direction is on AB5 type intermetallic system

(LaNi5). We have carried out material tailoring through

substitution on the Ni site by the most feasible elements Co

and Fe substitution. Although substitutions by Co and Fe were

investigated, optimum results were obtained only through Fe

substitution. The higher electron attractive power of Fe (3d6 as

against 3d8 of Ni) is expected to lead to the possibility of

putting higher number of hydrogen atoms in the unit cell,

thus resulting in higher storage capacity. The size of the Fe

atom (1.72 A) is higher than that of Ni (1.67 A) by about 2.99%.

This may lead to the larger size of interstitial voids. Thus,

there may be higher number of interstitial voids occupied by

Fig. 3 – Experimental and simulated desorption P–C

Isotherms of La(Ni0.84Fe0.16)5.

hydrogen for the Fe-substituted version as compared to Ni

alone. It has been found that all the phases of La(Nil � xFex)5exhibit better hydrogen storage characteristics than the

parent material LaNi5. Thus, storage capacity of La(Nil � xFex)5for x¼ 0, 0.05, 0.10, 0.16, 0.25, 0.30 are w1.50, 1.93, 1.95, 2.40,

1.78 and 1.60 wt%, respectively. The material La(Ni0.84 Fe0.16)5exhibits the highest storage capacity of w2.40 wt% H2. Such

improvements still do not take us to the required storage

capacity of w3 wt% (WE-NET, Japan limit) or >6.5 wt% (US

DOE limit). Material tailoring of intermetallic hydrides is being

pursued so as to increase storage capacity further. In the case

of intermetallic alloys, besides material tailoring to obtain

high storage capacity, computer simulation of P–C Isotherms

has also been done to check the thermodynamic viability of

the material. Fig. 3 shows the experimental and simulated P–C

Isotherm of La(Ni0.84 Fe0.16)5 using mathematical model

described by Singh, R. K. et al. [33]. Considerable attention has

also been paid to study: (a) MgH2 and Mg-based composite

materials and (b) built-in lightweight complex hydrides such

as NaAlH4, Mg(AlH4)2, LiAlH4, LiNH2/Li2NH etc.

4.2. Lightweight composite materials for hydrogenstorage

Recently, attention has turned on hydrides of light elements

such as Li, B, C, N, Na, Mg and Al, etc. One promising

material which is under focus is MgH2 [34]. The prime reason

is that Mg is a light element and it is comparatively less

expensive. Most importantly, the storage capacity of the Mg

binary hydride is w7.6 wt% H2. However, Mg is not a prac-

tical storage material because hydriding and dehydriding

kinetics of Mg is very slow at ambient conditions. In order to

enhance the hydrogen storage characteristics, new Mg-based

composites have been developed [35]. Some elucidative

examples of the Mg-based composites which have been

extensively investigated are:

� Mg–x wt% LaNi5 type storage materials

� Mg–x wt% Mg2Nil � xCox (or Fex) type storage materials

These Mg-based composite materials may be the ideal

hydrogen storage systems for vehicular transport since these

are lightweight materials and also the decomposition

temperature ranges from w50 to w100 �C, which can be easily

available through the engine exhaust.

4.3. Carbon nanomaterials

Porous carbon structure is another interesting system for

hydrogen adsorption [36]. Many improvements have been

Fig. 4 – (a). Desorption kinetics with respect to CNT

concentration in NaAlH4 (for details please see ref [48]). (b).

Recycling behavior of Mm doped NaAlH4 (for details please

see ref [49]).


achieved in synthesizing microporous carbonaceous mate-

rials with very high hydrogen adsorption properties [37–42].

Carbon nanotubes (CNTs) and graphitic nanofibers (GNFs)

have been considered as promising candidates for reversible

hydrogen storage [37,38]. However, considerable confusion

still exists regarding hydrogen storage after the early rather

dramatic results [39] in regard to very high hydrogen storage

capacities (up to w67 wt%) for GNF. Several investigators have

attempted to find the reason for such high hydrogen storage

capacities. Although it has not been possible to pin point the

exact reason for the high hydrogen storage capacities

exhibited by GNF, some general features governing the high

storage capacities have become discernible. It has been sug-

gested that mobility of the hydrogen may get suppressed and

hydrogen molecules get agglomerated in a liquid like config-

uration. We have in our lab carried out investigations on

hydrogenation behavior of carbon (graphitic) nanofibers [40]

and are trying to establish the reproducible capacity.

The formation of graphitic nanofibers is achieved through

catalyst-assisted thermal cracking of hydrocarbons. The

catalyst employed is often nickel, copper powder or a mixture

of the two (e.g. 98 wt% Ni and 2 wt% Cu). The hydrocarbons

employed are acetylene (C2H2), ethylene (C2H4) or benzene

(C6H6) [41]. The yield obtained through these catalyst-assisted

cracking process is rather poor and also the resulting GNFs are

randomly oriented. In order to improve upon this, we

employed Fe, Co, Ni, Mo, Pd catalysts in the form of films and

sheets [42]. It has been found that Pd sheets give optimum

results in regard to the yield and orientation of the as-grown

GNFs. This is in contrast to the earlier results on growth of

GNFs employing Cu and Ni powders as catalysts where the

resulting GNFs are randomly oriented. Seeking analogy from

the formation of carbon nanotubes, where oriented CNTs

grow when the catalyst particles are patterned, it may be

taken that with catalyst in the form of a sheet with juxtapose

grains, oriented GNFs will result. The GNFs grown by us have

shown storage capacity of in excess of 10 wt% and up to

17 wt% H2 [42].

4.4. Complex metal hydrides

Complex hydrides are actually built-in hydrides. Unlike

intermetallic hydrides, the hydrogen in the complexes is

tightly bonded with the parent material by strong covalent

and/or ionic bonding. The number of hydrogen atoms per

metal atom (H/M ratio) is two in many cases [43]. These

complex hydrides show high gravimetric storage capacity at

room temperature (e.g. LiBH4–18 wt% H2). But, the low

hydrogen liberation kinetics even at very high temperature

and irreversibility is the disadvantage for the practical use of

these hydrides. Various studies on the alkali/alkaline earth

metal aluminium hydrides and borohydrides have been

carried out [44,45]. Among all complex-based aluminum

hydrides, sodium alanate has received considerable attention

due to its high hydrogen capacity (7.44 wt%) and favorable

thermodynamics for reversible hydrogen storage [46]. The two

step reactions together (3NaAlH4 / Na3AlH6þ 2Alþ 3H2 and

Na3AlH6 / 3NaHþAlþ 3/2H2) liberate 5.55 wt% H2, which is

very close to the US DOE limit of gravimetric hydrogen

capacity. The decomposition temperature looks still higher

and it is kinetically very slow (>50 h for first step reaction at

w150 �C and 30 h for second step reaction at>200 �C). Besides,

the products of decomposition do not combine with hydrogen

to form the initial alanate phase again. However, in 1997,

Bogdanovic and Schwickardi [47] demonstrated that sodium

alanate is a viable means of reversible hydrogen storage

system by deploying transition metal catalysts (Ti, Zr, etc.).

This has triggered the interest in NaA1H4 as a reversible

hydrogen storage system and there has been a great deal of

effort to find better catalysts like Ti for sodium alanate. Better

alternative catalysts may exist that can improve the dehy-

drogenation kinetics and long-term reversibility in ambient

conditions. While transition elements (mainly Ti, Zr and Fe)

have been proposed as promising catalysts by several

workers, we have investigated the feasibility for the use of

NaAlH4 by new alternative catalysts [48,49]. We have intro-

duced carbon nanotubes (CNTs) as a catalyst for NaAlH4

Fig. 5 – Desorption kinetics of alanate mixture:

xMg(AlH4)2 D yNaAlH4 (0 < x < 1, y ‡ 1) (for details please

see ref [45]).


system. The main advantage of using CNT as a catalyst is its

high outer surface area (w1315 m2/g). In addition to the nano-

size, its high aspect ratio (diameter from w10 to w30 nm and

length from w1 to w10 mm) can provide additional surface/

interface in the host material, where they are admixed. The

CNTs are also known to possess significant catalytic activity

via p and s bonds, particularly the latter associated with

carbon in graphitic sheets. Multi-walled carbon nanotubes

(MWNTs) were synthesized in our lab through thermal spray

technique. A suitable amount of CNTs in 2,4,6,8 and 12 mol%

has been taken with NaAlH4 and this mixture was mechan-

ically admixed for 5 min at a milling speed of w5500 rpm (vial

volume w40 cm3) under argon atmosphere. Out of various

Fig. 6 – Recycling behavior of ball-milled 2:1.1 molar

mixtures of LiNH2 and MgH2 at 200 8C (for details please see

ref [50]).

proportions, NaAlH4–x mol% CNT (x¼ 2, 4, 6, 8 and 12), we

have found that the material with x¼ 8 mol% is the optimum

material (as shown in Fig. 4(a)). It shows the highest desorp-

tion rate, leading to w3.3 wt% of H2 at w160 �C within 2 h. The

CNT admixed NaAlH4 has also been found to exhibit good

rehydrogenation characteristics [48]. CNT catalyst is found to

be better than other carbon-based catalysts such as graphite

and activated carbon. We have continued our studies for

finding new catalysts (other than CNTs). We have observed

very interesting results when nanoform of Mischmetal (Mm:

Ce-42 at%, La-31 at%, Nd-18 at%, Pr-9 at%) is used as catalyst

[49] (refer to Fig. 4(b)). Apart from sodium alanate, other ala-

nates such as lithium alanate and magnesium alanate are

attractive candidates because of their high gravimetric

hydrogen capacity. We have observed some interesting

results on mixtures of NaAlH4 and Mg(AlH4)2. In the alanate

mixture, 0.5Mg(AlH4)2þNaAlH4, the dehydrogenation

temperature of NaAlH4 gets lowered by w50 �C (from w190 �C

to 140 �C) with 4 times faster desorption kinetics [45]. Fig. 5

shows the desorption kinetics of xMg(AlH4)2þyNaAlH4

(0< x< 1, y� 1). In the series of complex hydrides, we have

also studied lithium amide/imide. One interesting result

obtained by us relates to the formation of Mg(NH2)2 on ball-

milling LiNH2 and MgH2 [50]. The hydrogen uptake capacity of

prolonged ball-milled LiNH2 and MgH2 at 200 �C has been

observed to be 4.3 wt% in 2 h. Fig. 6 shows the recycling

behavior of ball-milled LiNH2 and MgH2 mixture. The unfa-

vorable thermodynamics of these hydrides for reversible

hydrogen storage restricts their use. These systems need

extensive R&D works to achieve a matured hydrogen storage

technology. We are continuing our R&D efforts in this

direction.

5. Applications

5.1. Hydrogen fueled vehicular transport

As pointed out in the ‘Introduction’ section for India, climate/

environmental change and its deleterious effects require

immediate change to hydrogen. India being an agricultural

country, the economy is dominantly dependent on it. The

climate change out of its various manifestations will influence

agriculture in India in a significant way. It may be pointed out

that about a decade back, the climate change was mostly

gauged by temperature rise. Preliminary predictions of the

influence of temperature rise in various areas including agri-

culture were made. However, based on IPCC reports and the

Nicholas Stern Report (October 2006), specific consequences of

climate change on agriculture have become available. As for

example, it was getting about 12 monsoon depressions in

a year. By 2000, it has dropped to about 4 per year. It has also

become proven now that northern India will become warmer.

Rainfall will decrease in Punjab, Rajasthan, Tamil Nadu and

some other states. All this will lower our agricultural

production. Rainfall will increase particularly along the

western coast and west central India, affecting agriculture in

Gujarat, Maharastra, and Karnataka. India has been marked in

the Nicholas Stern report as one of the most sensitive coun-

tries in relation to effect of climate change on agriculture.

Fig. 7 – Hydrogen/hydride heat exchanger tank coupled

with Internal Combustion engine of a four-wheeler.


In view of the above, it is clear that India should be the first

country to start using hydrogen as a fuel. This is the best way

to combat climate change. For realizing this, we must have

working modules of devices, particularly vehicles running on

hydrogen as fuel. In the following, we proceed to describe and

discuss these developments on hydrogen-fueled vehicles

carried out at the Hydrogen Energy Center (HEC), BHU.

After production and storage, the next step towards the

hydrogen economy is the application. The main focus for the

application aspect at the BHU is vehicular transport. This is

because out of the two commercial energies required – elec-

tricity and oil (for motive power), the latter possesses a bigger

challenge. Whereas coal powered super thermal, nuclear and

hydroelectric generation are expected to take care of electrical

requirements, the same is not true for oil. India requires at

present about w160 MT of oil of which we have to import

122 MT. With urban air pollution, climate change (CO2 emis-

sion), available land area (inadequacy of use of biofuels and

food versus fuel crisis through use of biofuels like biodiesel),

the economic costs of oil dependence (including price rise

risks), hydrogen as a fuel is a clear winner. Thus, use of

hydrogen as road transport fuel is of utmost importance. BHU

Hydrogen Energy Center, in regard to the application question,

has focused on R&D and demonstration of hydrogen fueled

road transport, particularly two-wheelers, three-wheelers and

small cars. It is difficult to make an internal combustion

engine run on hydrogen fuel, because of significantly different

properties of hydrogen as compared to petroleum, particularly

the density (density 0.0892 g/l, 7% density of air) and the self-

ignition energy (0.02 mJ as compared to petroleum for which it

is 0.29 mJ), among other things. One key to increasing the

power of a hydrogen fueled Internal Combustion (IC) engine is

to increase the compression ratio. The self-ignition tempera-

ture of H2 is w630 �C as compared to petrol, it is 230 �C. Thus,

higher compression ratios leading to higher thermal efficiency

can be achieved with hydrogen as a fuel. This aspect is being

studied at BHU. We have found that compression ratio for our

hydrogen fueled two and three-wheelers can be increased

from w8 to w11.

5.2. Examples of hydrogen fueled vehicular transportdeveloped at BHU: two, three and four-wheelers

The hydride powder is filled in the heat exchanger system

which is coupled to IC engine exhaust gas (which is mostly

steam in the case of hydrogen). The hydride of choice has been

MmNi4.6Fe0.4 (storage capacity w1.8 wt% H2). Some trials have

also been done using Ti admixed NaAlH4. The total quantity of

hydride employed is w20 kg. The exhaust gas coming out at

temperatures of w60 �C in the case of two-wheelers is circu-

lated in the hydride heat exchanger bed. Since thermal

conductivity of the hydride is very poor (0.5–1.0 W/mK),

a hydride heat exchanger tank (HHET) has been designed. The

HHET is located below the driver’s seat. To heat the hydride

effectively by the exhaust heat of the engine, 20 kg of hydride

is distributed in the HHET by 20 aluminum tubes of 1-in

diameter and 12-in length. The exhaust heat from the 100 cc

two-wheeler engine is able to raise the temperature of hydride

to w60 �C. This results in continuous emission of hydrogen

which is sent to the engine. An important point is the site and

timing of hydrogen injection in the engine. We have found

that for knock-free operation hydrogen injection near the

engine inlet valve is best. Hydrogen is introduced during the

suction stroke at 25 �C before the top dead center. The

hydrogen entry on and off time is controlled through a cam

located in the engine head.

Most of our work on development of the hydrogen fueled IC

engine is on two-wheelers. These have achieved from w60 to

w80 km driving range in a single charge. With higher storage

capacity hydride, this range can be increased. We have

recently developed Mm (La rich, i.e. La> 35%) –Ni–Fe hydride

with a storage capacity of w2.4 wt%. We are now in the

process of using this hydride. The range is expected to become

from w80 to w100 km. The work is being extended to three-

wheelers and small cars (refer to Fig. 7). Previously, we

mounted the hydride tank at the side of the vehicle; this is the

position of the silencer for conventional two-wheelers. For the

hydrogen/hydride fueled two-wheeler, the hydride heat

exchanger tank is so designed that it works as a silencer.

In India, two-wheelers are used for personalized transport;

three-wheelers are used for passenger transport. The HEC at

Banaras Hindu University seeks to persuade industry to

produce hydrogen fueled two and three-wheelers. Thus, we

have converted a petrol-driven three-wheeler manufactured

and provided by International Cars and Motors Limited (ICML),

Jallandhar (Punjab) to run on hydrogen stored in Mm–Ni–Fe

hydride (refer to Fig. 8). A 40 kg hydride tank which we have

developed was interfaced with the 1.75 HP internal combus-

tion engine exhaust of the three-wheeler. The hydrogen was

injected through a timed manifold injection. The average

distance traveled by a three-wheeler vehicle per day is

Fig. 8 – Demonstration of 3-wheeler developed by Physics

Department, Banaras Hindu University for International

Cars and Motors Ltd., under BHU-ICML-UGC-MNES

programme in AUTO-EXPO 2006 held at New Delhi.


w30 km. In a single charge, the average distance travelled by

the hydrogen fueled three-wheeler is about 60 km at a top

speed of w50 kmph. The ICML engineers have been trained to

convert these wheelers to run on hydrogen.

In India, the ICML is in the process of manufacturing 10

three-wheelers. These will run between the Central Secre-

tariat and Lodhi Road, New Delhi. This naturally makes

hydrogen motorized transport obvious to all and sundry at the

heart of the nation’s capital. This will be followed by

production of 100 hydrogen three-wheelers. Similar efforts are

being made for two-wheelers with the help of the Society for

Indian Auto Manufacturers (SIAM), which has access to

various two-wheeler manufacturers in India. Both these

efforts to introduce hydrogen fueled small vehicles in India

are being made in collaboration with the Ministry of New and

Renewable Energy (MNRE), Government of India.

6. Conclusions

This paper reviews the R&D activities of Hydrogen Energy

Center, BHU in production, storage and application of

Hydrogen Energy. We have developed hydrogen fueled two-

wheelers. This work is being extended to three-wheelers and

small cars. The hydrogen fueled vehicles developed at

Hydrogen Energy Center, BHU have nearly the same perfor-

mance as that of the petrol fueled vehicles but with no impact

on the climate change. At present we have developed vehicles

running in the range of w60–80 km for two-wheelers and

w60 km for three-wheelers (at top speed of w50 km/hr) for

single charging. Commercialization efforts on hydrogen

fueled vehicular transport are being done by Hydrogen Energy

Center, BHU with the help of Indian auto industries.

The use of environmentally friendly and renewable fuel,

hydrogen, needs more investment, more R&D and more

general acceptance as an idea whose time has come.

Acknowledgements

The authors would like to thank Prof. T.N. Veziroglu, Prof. A.R.

Verma, Prof. C.N.R. Rao, Prof. R. Chidambaram, Prof. S.K. Joshi,

Prof. S. P. Thyagrajan and Prof. D.P. Singh (VC:BHU) for their

encouragement and support. Financial support from the

Ministry of New and Renewable Energy and the University

Grants Commission are thankfully acknowledged.

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