Browsing by Author "D. Pukazhselvan"

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Carbon nanostructures as catalyst for improving the hydrogen storage behavior of sodium aluminum hydride
(2012) M. Sterlin Leo Hudson; Himanshu Raghubanshi; D. Pukazhselvan; O.N. Srivastava
The present paper reports the catalytic effect of carbon nanomaterials, particularly carbon nanotubes (CNTs) and graphitic nanofibres (GNFs) with two different structure morphology, namely planar GNFs (PGNFs) and helical GNFs (HGNFs) as the catalyst for improving the dehydrogenation and rehydrogenation behavior of sodium aluminum hydride (NaAlH 4). It has been observed that HGNFs posses superior catalytic activity than other carbon nanoforms in improving the desorption kinetics and decreasing the desorption temperature of NaAlH 4. Temperature programmed desorption (TPD) reveals that HGNFs admixed NaAlH 4 undergo hydrogen desorption at a much lower temperature than PGNFs and CNTs (SWCNTs and MWCNTs) admixed NaAlH 4. Thus for the heating rate of 2 °C/min, the peak desorption temperature corresponds to initial step decomposition of NaAlH 4 admixed with 2 wt.% HGNFs and 2 wt.% PGNFs has been lowered to 143.6 °C and 152.6 °C, respectively (for pristine NaAlH 4, it is ∼170 °C). In addition to the enhancement in desorption kinetics, the HGNFs admixed NaAlH 4 undergoes fast rehydrogenation at the moderate condition. Microstructural investigation reveals that the HGNFs were present on the surface of NaAlH 4 grains, whereas CNTs were tunneled into the grains of NaAlH 4 suggesting a distinct catalytic behavior of different carbon nanovariants. © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Carbon nanostructures as catalyst for improving the hydrogen storage behaviour of complex aluminium hydride
(2010) M. Sterlin Leo Hudson; Himanshu Raghubanshi; D. Pukazhselvan; O.N. Srivastava
The present paper reports the catalytic effect of carbon nanostructures, particularly graphitic nanofibres (GNFs) with different structure morphology, namely helical GNFs (HGNFs) and planar GNFs (PGNFs) as the catalyst for complex aluminium hydride. HGNFs and PGNFs were synthesized by catalytic thermal decomposition of acetylene (C2H2). The growth of HGNFs was achieved by employing faceted Ni nanoparticles, whereas spherical Ni nanoparticles produce PGNFs. It has been observed that HGNFs posses superior catalytic activity than PGNFs in improving the desorption kinetics and decreasing the desorption temperature of complex aluminium hydride (NaAlH 4, LiAlH4 and LiMg(AlH4)3). Temperature programmed desorption (TPD) reveals that HGNFs admixed alanates undergo hydrogen desorption at a much lower temperature than PGNFs admixed material. Thus for the heating rate of 2°C/min, the peak desorption temperature corresponds to initial step desorption of NaAlH4 admixed with 8 mol% HGNFs and 8 mol% PGNFs has been lowered to 143.6°C and 152.6°C, respectively. In addition to the enhancement in desorption kinetics, the GNFs admixed NaAlH4 also undergoes rehydrogenation at the moderate condition. In order to get supportive evidence for our experiment, we have carried out abinitio studies by calculating hydrogen removal energy from alanates with planar and helical model of GNF. It becomes clear that from both experiment and ab-initio calculations, that catalytic effect of GNFs is curvature dependent. Thus HGNF with higher helicity helps to lower the energy needed to remove hydrogen from alanates.
Direct synthesis of sodium alanate using mischmetal nanocatalyst
(2012) D. Pukazhselvan; M. Sterlinleo Hudson; O.N. Srivastava
This study reports the synthesis of NaAlH 4 by ball milling of NaH and Al mixture along with 3 mol % Mischmetal (Mm) nanocatalyst under hydrogen atmosphere. It is observed that synthesis of the intermediate phase Na 3AlH 6 can be achieved by ball milling even under 1 atm hydrogen at room temperature. Ball milling of the NaH + Al with 3 mol % Mm with 3 atm hydrogen in excess of 40 h time did not lead to the formation of NaAlH 4 but charging of the milled material at 100 atm hydrogen pressure at 120 °C lead to formation of NaAlH 4 phase. Direct synthesis of NaAlH 4 was achieved by milling of NaH + Al with 3 mol % Mm under 100 atm hydrogen pressure. Direct synthesis is possible even without any catalyst by high pressure milling. However catalyst is required to improve the hydrogen sorption characteristics of the synthesized material. The as-prepared Mm catalyzed NaAlH 4 is also found to reversibly store hydrogen up to 4.2 wt% hydrogen. Catalytic activity is attributed to defects promoted by ball milling and catalysts. © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Effects of helical GNF on improving the dehydrogenation behavior of LiMg(AlH4)3 and LiAlH4
(2010) M. Sterlin Leo Hudson; Himanshu Raghubanshi; D. Pukazhselvan; O.N. Srivastava
The present paper reports the effect of graphitic nanofibres (GNFs) for improving the desorption kinetics of LiMg(AlH4)3 and LiAlH4. LiMg(AlH4)3 has been synthesized by mechano-chemical metathesis reaction involving LiAlH4 and MgCl2. The enhancement in dehydrogenation characteristics of LiMg(AlH4)3 has been shown to be higher when graphitic nanofibres (GNFs) were used as catalyst. Out of two different types of nanofibres namely planar graphitic nanofibre (PGNF) and helical graphitic nanofibre (HGNF), the latter has been found to act as better catalyst. We observed that helical morphology of fibres improves the desorption kinetics and decreases the desorption temperature of both LiMg(AlH4)3 and LiAlH4. The desorption temperature for 8 mol% HGNF admixed LiAlH4 gets lowered from 159 °C to 128 °C with significantly faster kinetics. In 8 mol% HGNF admixed LiMg(AlH4)3 sample, the desorption temperature gets lowered from 105 °C to ∼70 °C. The activation energy calculated for the first step decomposition of LiAlH4 admixed with 8 mol% HGNF is ∼68 kJ/mol, where as that for pristine LiAlH4 it is 107 kJ/mol. The activation energy calculated for as synthesized LiMg(AlH4)3 is ∼66 kJ/mol. Since the first step decomposition of LiMg(AlH4)3 occurs during GNF admixing, the activation energy for initial step decomposition of GNF admixed LiMg(AlH4)3 could not be estimated. © 2009 Professor T. Nejat Veziroglu.
Graphitic Nanofibres as Catalyst for Improving the Dehydrogenation Behavior of Complex Aluminium Hydrides
(Forschungszentrum Julich GmbH, 2010) M. Sterlin Leo Hudson; Himanshu Raghubanshi; D. Pukazhselvan; O.N. Srivastava
In the present work, we explored the catalytic effect of graphitic nanofibres (GNF) particularly of two different morphology, namely planar graphitic nanofibre (PGNF) and helical graphitic nanofibre (HGNF) for enhancement of hydrogen desorption from complex aluminium hydrides such as LiAlH4 and LiMg(AlH4)3. We found that the catalytic activity of fibres depends mainly on its morphology. Hence helical morphology fibres possess superior catalytic activity than planar graphitic nanofibres. The desorption temperature for 8 mol% HGNF admixed LiAlH4 gets lowered from 159°C to 128°C with significantly faster kinetics. In 8 mol% HGNF admixed LiMg(AlH4)3 sample, the desorption temperature gets lowered from 105°C to ~70°C. The activation energy calculated for the first step decomposition of LiAlH4 admixed with 8 mol% HGNF is ~68 kJmol-1, whereas that for pristine LiAlH4 it is 107 kJ/mol. The activation energy calculated for as synthesized LiMg(AlH4)3 is ~66 kJ/mol. Since the first step decomposition of LiMg(AlH4)3 occurs during GNF admixing, the activation energy for initial step decomposition of GNF admixed LiMg(AlH4)3 could not be estimated. © 2010 18th World Hydrogen Energy Conference 2010, WHEC 2010, Proceedings. All Rights Reserved.
Hydrogen energy in changing environmental scenario: Indian context
(2009) M. Sterlin Leo Hudson; P.K. Dubey; D. Pukazhselvan; Sunil Kumar Pandey; Rajesh Kumar Singh; Himanshu Raghubanshi; Rohit. R. Shahi; O.N. Srivastava
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 photoelectrochemical 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 fabricated to get high hydrogen production rate (∼10.35 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 (x = 0.16) has been found to yield a high storage capacity of ∼2.40 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 (∼3.3 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 circumventing climate change. © 2009 International Association for Hydrogen Energy.
Hydrogen energy in Indian context and R&D efforts at Banaras Hindu University
(2007) P.R. Mishra; D. Pukazhselvan; M. Sterlin Leo Hudson; Sunil Kumar Pandey; O.N. Srivastava
This paper describes Hydrogen energy in India and R&D efforts at Banaras Hindu University. All the three important ingredients i.e. production, storage and application of hydrogen have been dealt with. As regards hydrogen production, we have described and discussed the solar route consisting of photoelectrochemical electrolysis of water. Nanostructured TiO2 films have been synthesized through hydrolysis of Ti[OCH(CH3)2]4. This has been used as photoanode. Modular designs of TiO2 photoelectrode based PEC cells have been fabricated to get high rate of hydrogen production (∼10.35 Lh-1m-2). Regarding storage which appears to be most crucial issue at present, we have discussed the intermetallic as well as complex hydride systems. For intermetallic we have dealt with materials tailoring of LaNi5 through Fe substituion. The La(Ni1-xFex)5 (x=0.16) has been found to yield to high storage capacity of ∼2.40wt%. We have also described and discussed the hydrogen storage in carbon nanofibres. Here storage capacity in excess of ∼10wt% has been obtained. We have shown that CNT admixing in NaAlH4 helps to circumvent the low desorption rate of hydrogen in NaAlH4. For 8 mol % CNT admixing, we have found the desorption rate to increase from ∼3.3 in more than 50 hrs to within 2 hrs. Relating to applications, we have focused on use of hydrogen (stored in intermetallic La-Ni-Fe system) as fuel for IC engine based vehicular transport particularly 2 and 3-wheelers (and small car). The 2 and 3-wheeler have nearly the same performance as the petrol fueled vehicles. At present we have vehicle range of ∼60-80 kms for 2-wheelers and ∼60 kms for 3-wheelers (at top speed of ∼50 kms/hr). Commercialization efforts on hydrogen fueled vehicular transport is being done by BHU:HEC with the help of Indian auto industries. © 2007 Taylor & Francis.
Hydrogen storage characteristics of CNT doped NaAlH4
(2006) D. Pukazhselvan; M. Sterlin Leo Hudson; Bipin Kumar Gupta; O.N. Srivastava
The current Hydrogen based energy infrastructure required a high energy density consumer friendly hydrogen storage media. Although the desired goals for the hydrogen fueled vehicular transport has not yet met by any hydrogen storage material, complex Sodium Alanate is said to be a promising candidate under this demand due to its high hydrogen storage capacity and the thermodynamically permissible reversible hydrogen storage capacity. However its poor sorption behavior under moderate conditions (NaAlH4→ Na 3AlH6; 3.7 wt % vs 50 hrs at ∼170°C and Na 3AlH6→ NaH; 1.85 wt % vs 30 hrs at ∼220°C) urges their limited uses in ages. But these limitations can be removed by using catalysts particularly transition elements but the location of catalyst in NaAlH4 matrix and the possible mechanism is not yet clearly understood. The aim of the present investigation is to improve the overall sorption characteristics of NaAlH4 by a new light weighted high surface area (1315 sq mtr/gm) material (CNT) admixing and to obtain a best doping level to NaAlH4. So far only Ti has been attempted as a suitable catalyst. It is believed that the high surface area of CNT can provide an additional solid-gas (H2) surface/interface and it can produce thermal contact between grains (thermal conductivity Kth of MWCNT: 3000 w/k and Kth of NaAlH4: 0.32 w/k) for stimulating their thermally activated dissociation in NaAlH4. In parallel with this approach XRD of NaAlH4 reveals that there was no change in lattice structure after doping by CNT, SEM picture depicts that CNT precipitation in grain surfaces. Catalytic concentration of various mole % of x values finds that x = 8 is the best doping level as it gives 3.3 wt % of hydrogen within 2 hrs. The comparative sorption behavior with Ti:NaAlH 4 also shows CNTs as an optimum alternative catalyst to NaAlH 4 and besides this CNT doped desorbed ingredients shown good rehydrogenation behavior(3.7 wt % at 8th cycle & 4.2 wt % maximum at elevated temperatures). We are trying for catalyzing NaAlH4 with some new transition m metal catalysts which leads better desorption rate and recyclability.
Investigation on the synthesis and quantum confinement effects of pure and Mn2+ added Zn(1-x)CdxS nanocrystals
(2011) R. Sakthi Sudar Saravanan; D. Pukazhselvan; C.K. Mahadevan
Zn(1-x)CdxS and Zn(1-x)Cd xS:Mn2+ semiconductor quantum dots (2-4 nm) have been prepared by a novel solvothermal route assisted microwave heating method. The growth parameters governing the smaller size and higher yield have been optimized. The synthesized QDs exhibit a significant blue shift as compared to their corresponding bulk counterpart in the UV-vis optical absorption spectrum. The dielectric constant value varies from 2.79 to 6.17 (at 40 °C, 1 kHz) depending upon the composition of the alloy; lower value corresponds to Zn 0.75Cd0.25S:Mn2+ and the higher value corresponds to Zn0.25Cd0.75S:Mn2+. The crystallite size to exciton bohr radius ratio being <1 indicates a strong quantum confinement effect in both CdS and ZnS QDs. The quantum confinement effect exists in the sequence of ZnS:Mn2+ < Zn (1-x)CdxS:Mn2+ (x < 0.5) < ZnS < Zn(1-x)CdxS < CdS < CdS:Mn2+. © 2011 Elsevier B.V. All rights reserved.
Investigations on hydrogen storage behavior of CNT doped NaAlH4
(2005) D. Pukazhselvan; Bipin Kumar Gupta; Anchal Srivastava; O.N. Srivastava
In this paper, we have carried out investigations on admixing carbon nanotubes (CNT) to increase the desorption rate of hydrogen in NaAlH 4. So far only transition metal Ti has been attempted as the suitable dopant for making NaAlH4 (purified version) a viable hydrogen storage material by increasing the hydrogen desorption rate. Out of the various materials corresponding to NaAlH4-x mol% CNT (x = 2, 4, 6, 8 and 12), we have found that the material with x = 8 mol% is the optimum material. It shows highest desorption rate leading to 3.3 wt.% of H2 at ∼160 °C within 2 h for the first dissociation reaction. The CNT admixed NaAlH4 has also been found to exhibit good rehydrogenation characteristics (reversibility on hydrogenation up to ∼4.2 wt.%). A feasible mechanism for the improvement of hydrogen desorption characteristics has been put forward. © 2005 Elsevier B.V. All rights reserved.
Investigations on some complex hydrides
(2008) D. Pukazhselvan; M. Sterlin Leo Hudson; G. Irene Sheeja; O.N. Srivastava
[No abstract available]
Investigations on the desorption kinetics of Mm-doped NaAlH4
(2007) D. Pukazhselvan; M. Sterlin Leo Hudson; Bipin Kumar Gupta; M.A. Shaz; O.N. Srivastava
This paper reports mischmetal (Mm) as an effective catalyst for fast desorption kinetics (3.7 wt% in 60 min in which ∼3.3 wt% observed in 30 min and ∼5 wt% in 180 min at the desorption temperature of 150 °C for the 2 mol% Mm-doped material) and rehydrogenation (up to 35 cycles) of the light weight hydrogen storage material NaAlH4. In fact this catalyst Mm has been shown to be better than the presently known catalyst Ti. For Mm, its presence when admixed in NaAlH4 is discernible. Also the higher reversible hydrogen storage capacity (4.77 wt% which is 86% of the total reversible storage capacity) of the total is achievable in the 12th cycle. The possible modes of catalyst Mm for fast desorption kinetics has been outlined and the most feasible mechanism in terms of weakening of Na and AlH4 bonding has been put forward. © 2006 Elsevier B.V. All rights reserved.
One step high pressure mechanochemical synthesis of reversible alanates NaAlH4 and KAlH4
(Elsevier Ltd, 2015) D. Pukazhselvan; Duncan Paul Fagg; O.N. Srivastava
The present study suggests high pressure mechanochemical treatment is a better strategy for The synthesis of performance enhanced reversible alanates. The reactants NaH/KH + Al along with catalysts (TiCl3, TiF3 and TiO2) milled under 100 bar hydrogen pressure for 30 h effectively transforms to products (NaAlH4 and KAlH4) in a single step. The as-synthesized NaAlH4 and KAlH4 samples release hydrogen at The temperatures of ∼100 °C and 215 °C, respectively. The stability of The KAlH4 phase can be further reduced by extending The high pressure mechanochemical reaction time to 80 h. The XRD and TEM analysis of The residues observed after extracting The NaAlH4 from The TiCl3 catalyzed material confirms The presence of Ti-Al alloy and highly dispersed NaCl nanoparticles. Catalytic activity is therefore attributed to mechano-chemical activation which involves catalytically active species (for e.g. Ti-Al) and defects/vacancies/strain in The system. © 2015 Hydrogen Energy Publications, LLC.
Studies on metal oxide nanoparticles catalyzed sodium aluminum hydride
(Elsevier Ltd, 2010) D. Pukazhselvan; M. Sterlin Leo Hudson; A.S.K. Sinha; O.N. Srivastava
This paper reports the catalytic activity of several metal oxide nanoparticles such as TiO2, CeO2, La2O3, Pr2O3, Nd2O3, Sm2O3, Eu2O3 and Gd2O3 for NaAlH4. TiO2 was found to be the most effective catalyst. In order to find the size dependence of TiO2 nanoparticles on the catalytic activity, TiO2 nanoparticles of different sizes such as 5 nm, 25 nm, 150 nm and 200 nm have been used. TiO2 nanoparticles lower the desorption temperature of sodium alanate (NaAlH4) from ∼ 473 K to ∼373 K. Using 5 nm and 25 nm TiO2 catalysts ∼3 wt% hydrogen could be released within 5-7 min at 423 K. TiO2 (25 nm) catalyst lowers the activation energy of NaAlH4 to 67 kJ/mol H2, as compared to 119 kJ/mol H2 for the pristine material. This is better than Ti nanoparticles catalyst of similar size which lowers the activation energy up to 77 kJ/mol H2. The long-term reversible characteristics of 25 nm TiO2 admixed NaAlH4 up to 35 cycles and the phase structural features of the cycled samples are discussed. © 2010 Elsevier Ltd.
Studies on synthesis and dehydrogenation behavior of magnesium alanate and magnesium-sodium alanate mixture
(2007) M. Sterlin Leo Hudson; D. Pukazhselvan; G. Irene Sheeja; O.N. Srivastava
Magnesium alanate (Mg (AlH4)2) has been synthesized by mechanochemically activated metathesis reaction involving MgCl2 and NaAlH4. Its dehydrogenation kinetics and storage capacity has been studied by using Sievert's type apparatus. We have obtained dehydrogenation capacity of 2.7 wt% H2 from Mg (AlH4)2 + 2 NaCl during the first decomposition step at 140 {ring operator} C and 1.1 wt% H2 during second step decomposition at 280 {ring operator} C. Efforts were carried out to reduce NaCl content from the product using Soxhlet extraction technique. The Soxhlet extracted product gives the total dehydrogenation capacity of 4.7 wt% H2. To enhance the storage capacity, we have synthesized a complex hydride consisting of mixture: x Mg (AlH4)2 + y NaAlH4(0 < x < 1, y ≥ 1) . In the alanate mixture 0.5 Mg (AlH4)2 + NaAlH4, the dehydriding temperature of NaAlH4 gets lowered by ∼ 50 {ring operator} C (from 190 {ring operator} C to 140 {ring operator} C) with 4 times faster desorption kinetics. The total hydrogen liberated in 180 min from NaAlH4 + 0.5 Mg (AlH4)2 (+ NaCl) mixture at 140 {ring operator} C has been observed to be 3.7 wt% H2. © 2007 International Association for Hydrogen Energy.
Studies on the synthesis and characterization of Zn1-xCd xS and Zn1-xCdxS:Mn2+ semiconductor quantum dots
(2011) R. Sakthi Sudar Saravanan; D. Pukazhselvan; C.K. Mahadevan
Quantum dots (3-4 nm) of Zn1-xCdxS (both free of Mn2+ and with Mn2+ incorporated) were synthesized through a novel solvothermal-microwave irradiation technique. Detailed structural analysis of the Zn1-xCdxS and Zn1-xCd xS:Mn2+ (x = 0, 0.25, 0.5, 0.75 and 1) materials was carried out using powder X-ray diffraction technique. For all the compositions, the crystallite size was controlled to less than 1.5 nm. The optical energy gap for Zn1-xCdxS was found to vary from 3.878 to 2.519 eV and for Zn1-xCd1-xS:Mn2+ it varies from 3.830 to 2.442 eV when x is increased from 0 to 1. Overall, the optical energy gap could be tuned from a minimum of 2.442 eV to a maximum of 3.878 eV. DC conductivity analysis (from 40C to 150°C) and electrical energy gap analysis for all the compositions were also performed. The dc conductivity for Zn 1-xCd1-xS solid solutions varies from 0.3840 × 10-10 to 8.7782 × 10-10 mho/m at 150°C and for Zn1-xCd1-xS:Mn2+ it varies from 0.5751 × 10-10 to 9.8078 × 10-10 mho /m at 150°C (for x = 0 to x = 1). The method of synthesis and the results observed in this investigation may assist in the fabrication of optical devices when the required operational performance falls under the range observed in the study. © 2010 2011 Taylor & Francis.
Studies on the synthesis of cubic ZnS quantum dots, capping and optical-electrical characteristics
(2012) R. Sakthi Sudar Saravanan; D. Pukazhselvan; C.K. Mahadevan
This paper presents a comparative analysis of ZnS QDs synthesized by conventional and microwave heating techniques using zinc acetate and sodium sulphide reactants. The size of the quantum dots achieved by the latter technique (∼3 nm) is at least 30 times smaller than the former technique. Incorporation of excess Na 2S and microwave treatment are the important factors responsible for controlling the size of ZnS nanocrystals. Furthermore, the distribution of quantum dots is highly influenced by the addition of small amount of NaOH. The UV-vis analysis reveals that the band gap can be widened up to 3.94 eV (correspond to ∼3 nm ZnS) from 3.67 eV (correspond to bulk ZnS). Surprisingly better conductivity is observed for the widest band gap ZnS of the present study; this could be due to defects/vacancies present in the system and its influence in the band structure. The higher conductivity value is supported by the smaller activation energy value, smaller dielectric constant and higher dielectric loss, etc. The conduction is further explained by thermionic emission mechanism. © 2011 Elsevier B.V.
Studies on TiO2 nanoparticles as catalyst for enhanced desorption characteristics of NaAlH4
(2011) D. Pukazhselvan; A.S.K. Sinha; O.N. Srivastava
TiO2 (np) has been found to be an effective catalyst over ZrO2 (np) for improving the hydrogen storage characteristics of NaAlH4. TiO2 catalyst reduces the activation energy of NaAlH4 to a better extent than ZrO2. In the reversibly hydrogenated materials, a substantial reduction in the dehydrogenation temperature could be achieved using TiO2 catalyst. Such effect was not observed through ZrO2. The activation energy of the reversibly hydrogenated NaAlH4 catalyzed by TiO2 nanoparticles obtained in the present study (60 kJ/mol H2) is smaller than that of TiO2:NaAlH4 starting material (101.9 kJ/mol H 2). The stability of the intermediate phase Na3AlH 6 in the presence of TiO2 catalyst was studied through TPD and TPA analysis. XRD analysis confirms that only TiO2 gets reduced during dehydrogenation; therefore, the observed effect is attributed to the consequence of reduction of TiO2. © 2011 World Scientific Publishing Company.