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Research Paper On Hydrogen Energy Density

Marcelo Carmo | David L. Fritz | Jürgen Mergel | Detlef Stolten

Hydrogen is often considered the best means by which to store energy coming from renewable and intermittent power sources. With the growing capacity of localized renewable energy sources surpassing the gigawatt range, a storage system of equal magnitude is required. PEM electrolysis provides a sustainable solution for the production of hydrogen, and is well suited to couple with energy sources such as wind and solar. However, due to low demand in electrolytic hydrogen in the last century, little research has been done on PEM electrolysis with many challenges still unexplored. The ever increasing desire for green energy has rekindled the interest on PEM electrolysis, thus the compilation and recovery of past research and developments is important and necessary. In this review, PEM water electrolysis is comprehensively highlighted and discussed. The challenges new and old related to electrocatalysts, solid electrolyte, current collectors, separator plates and modeling efforts will also be addressed. The main message is to clearly set the state-of-the-art for the PEM electrolysis technology, be insightful of the research that is already done and the challenges that still exist. This information will provide several future research directions and a road map in order to aid scientists in establishing PEM electrolysis as a commercially viable hydrogen production solution. Copyright © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Gerda Gahleitner

An increasingly large percentage of power is being generated from renewable energy sources with intermittent and fluctuating outputs. Therefore there is a growing need for energy storage. With power-to-gas, excess electricity is converted into hydrogen by water electrolysis, which can be stored and, when needed, can be reconverted into electricity with fuel cells. Besides the energy vector for electricity, mobility and heat, hydrogen can be utilized as a raw material for the chemical industry or further be used for the synthesis of various hydrocarbon fuels such as methane. This article is an international review of numerous power-to-gas pilot plants that have either already been realized or are being planned. It provides information about their installed components and capacities as well as about operating experience that has been had with them. In many of the projects it was concluded that the design and sizing, control strategy and system integration of the power-to-gas plants have a great influence on their overall efficiency, reliability and economics. Topics for further research are the improvement of the efficiency, reliability, lifetime and costs of electrolyzers and fuel cells and better ways of dealing with power sources. In order to improve the overall performance, the reduction of auxiliary equipment and the continuous long-term operation of power-to-gas pilot plants will be necessary. The further development of codes and standards for permits to operate, as well as of hydrogen components and control strategies, would bring additional benefits for power-to-gas systems. It is also recommended that optimum system configurations and components be determined with regard to the available infrastructure and the type of application involved. Copyright © 2012, Hydrogen Energy Publications, LLC.

Lei Ge | Changcun Han | Xinlai Xiao | Lele Guo

Molybdenum disulfide (MoS 2 ) and graphitic carbon nitride (g-C 3 N 4 ) composite photocatalysts were prepared via a facile impregnation method. The physical and photophysical properties of the MoS 2 -g-C 3 N 4 composite photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microcopy (HRTEM), ultraviolet-visible diffuse reflection spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) spectroscopy. The photoelectrochemical (PEC) measurements were tested via several on-off cycles under visible light irradiation. The photocatalytic hydrogen evolution experiments indicate that the MoS 2 co-catalysts can efficiently promote the separation of photogenerated charge carriers in g-C 3 N 4 , and consequently enhance the H 2 evolution activity. The 0.5wt% MoS 2 -g-C 3 N 4 sample shows the highest catalytic activity, and the corresponding H 2 evolution rate is 23.10 μmol h -1 , which is enhanced by 11.3 times compared to the unmodified g-C 3 N 4 . A possible photocatalytic mechanism of MoS 2 co-catalysts on the improvement of visible light photocatalytic performance of g-C 3 N 4 is proposed and supported by PL and PEC results. © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights.

D. J. Durbin | C. Malardier-Jugroot

Hydrogen gas is increasingly studied as a potential replacement for fossil fuels because fossil fuel supplies are depleting rapidly and the devastating environmental impacts of their use can no longer be ignored. H 2 is a promising replacement energy storage molecule because it has the highest energy density of all common fuels by weight. One area in which replacing fossil fuels will have a large impact is in automobiles, which currently operate almost exclusively on gasoline. Due to the size and weight constraints in vehicles, on board hydrogen must be stored in a small, lightweight system. This is particularly challenging for hydrogen because it has the lowest energy density of common fuels by volume. Therefore, a lot of research is invested in finding a compact, safe, reliable, inexpensive and energy efficient method of H 2 storage. Mechanical compression as well as storage in chemical hydrides and absorption to carbon substrates has been investigated. An overview of all systems including the current research and potential benefits and issue are provided in the present paper. © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Ibrahim Dincer | Canan Acar

© 2014 Hydrogen Energy Publications, LLC. This paper examines various potential methods of hydrogen production using renewable and non-renewable sources and comparatively assesses them for environmental impact, cost, energy efficiency and exergy efficiency. The social cost of carbon concept is also included to present the relations between environmental impacts and economic factors. Some of the potential primary energy sources considered in this study are: electrical, thermal, biochemical, photonic, electro-thermal, photo-electric, and photo-biochemical. The results show that when used as the primary energy source, photonic energy based hydrogen production (e.g., photocatalysis, photoelectrochemical method, and artificial photosynthesis) is more environmentally benign than the other selected methods in terms of emissions. Thermochemical water splitting and hybrid thermochemical cycles (e.g. Cu-Cl, S-I, and Mg-Cl) also provide environmentally attractive results. Both photoelectrochemical method and PV electrolysis are found to be least attractive when production costs and efficiencies are considered. Therefore, increasing both energy and exergy efficiencies and decreasing the costs of hydrogen production from solar based hydrogen production have a potential to bring them forefront as potential options. The energy and exergy efficiency comparisons indicate the advantages of fossil fuel reforming and biomass gasification over other methods. Overall rankings show that hybrid thermochemical cycles are primarily promising candidates to produce hydrogen in an environmentally benign and cost-effective way.

M. Z.F. Kamarudin | S. K. Kamarudin | M. S. Masdar | W. R.W. Daud

Direct ethanol fuel cells have attracted much attention recently in the search for alternative energy resources. As an emerging technology, direct ethanol fuel cells have many challenges that need to be addressed. Many improvements have been made to increase the performance of direct ethanol fuel cells, and there are great expectations for their potential. However, many improvements need to be made in order to enhance the potential of direct ethanol fuel cells in the future. This paper addresses the challenges and the developments of direct ethanol fuel cells at present. It also presents the applications of DEFC. Copyright © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Shao Wen Cao | Yu Peng Yuan | Jun Fang | Mohammad Mehdi Shahjamali | Freddy Y.C. Boey | James Barber | Say Chye Joachim Loo | Can Xue

Well dispersed CdS quantum dots were successfully grown in-situ on g-C 3 N 4 nanosheets through a solvothermal method involving dimethyl sulfoxide. The resultant CdS-C 3 N 4 nanocomposites exhibit remarkably higher efficiency for photocatalytic hydrogen evolution under visible light irradiation as compared to pure g-C 3 N 4 . The optimal composite with 12 wt% CdS showed a hydrogen evolution rate of 4.494 mmol h -1 g -1 , which is more than 115 times higher than that of pure g-C 3 N 4 . The enhanced photocatalytic activity induced by the in-situ grown CdS quantum dots is attributed to the interfacial transfer of photogenerated electrons and holes between g-C 3 N 4 and CdS, which leads to effective charge separation on both parts. Copyright © 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Ke Jing Huang | Lan Wang | Yu Jie Liu | Yan Ming Liu | Hai Bo Wang | Tian Gan | Ling Ling Wang

Layered molybdenum disulfide (MoS 2 )-graphene composite is synthesized by a modified L-cysteine-assisted solution-phase method. The structural characterization of the composites by energy dispersive X-ray analysis, X-ray powder diffraction, Fourier transform infrared spectroscopy, XPS, Raman, and transmission electron microscope indicates that layered MoS 2 -graphene coalescing into three-dimensional sphere-like architecture. The electrochemical performances of the composites are evaluated by cyclic voltammogram, galvanostatic chargeedischarge and electrochemical impedance spectroscopy. Electrochemical measurements reveal that the maximum specific capacitance of the MoS 2 egraphene electrodes reaches up to 243 F g -1 at a discharge current density 1 A g -1 . The energy density is 73.5 Wh kg -1 at a power density of 19.8 kW kg -1 . The MoS 2 -graphene composites electrode shows good long-term cyclic stability (only 7.7% decrease in specific capacitance after 1000 cycles at a current density of 1 A g -1 ). The enhancement in specific capacitance and cycling stability is believed to be due to the 3D MoS 2 -graphene interconnected conductive network which promotes not only efficient charge transport and facilitates the electrolyte diffusion, but also prevents effectively the volume expansion/ contraction and aggregation of electroactive materials during chargeedischarge process. Taken together, this work indicates MoS 2 -graphene composites are promising electrode material for high-performance supercap acitors. Copyright © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

San Ping Jiang | Xinbing Chen

Intermediate temperature solid oxide fuel cells (IT-SOFCs) using chromia-forming alloy interconnect requires the development of cathode not only with high electrochemical activity but also with the high resistance or tolerance towards Cr deposition and poisoning. This is due to the fact that, at SOFC operating temperatures, volatile Cr species are generated over the chromia scale, poisoning the cathodes such as (La,Sr)MnO 3 (LSM) and (La,Sr)(Co,Fe)O 3 (LSCF) and causing a rapid degradation of the cell performance. Thus, a fundamental understanding of the interaction between the Fe-Cr alloys and SOFC cathode is essential for the development of high performance and stable SOFCs. The objective of this paper is to critically review the progress and particularly the work done in the last 10 years in this important area. The mechanism and kinetics of the Cr deposition and Cr poisoning process on the cathodes of SOFCs are discussed. Chromium deposition at SOFC cathodes is most likely dominated by the chemical reduction of high valence Cr species, facilitated by the nucleation agents on the electrode and electrolyte surface and/or at the electrode/electrolyte interface, i.e., the nucleation theory. The driving force behind the nucleation theory is the surface segregation and migration of cationic species on the surface of perovskite oxide cathodes. Overwhelming evidences indicate that the surface segregation plays a critical role in the Cr deposition. The prospect of the development in the Cr-tolerant cathodes for SOFCs is presented. Copyright © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Sebastian Schiebahn | Thomas Grube | Martin Robinius | Vanessa Tietze | Bhunesh Kumar | Detlef Stolten

© 2015 Hydrogen Energy Publications, LLC. The issue of limited fossil fuels combined with the vast technological improvements in recent years has initiated numerous installations of renewable power production, particularly in form of photovoltaic cells and wind turbines. Since the volatile character of wind and solar radiation leads to a fluctuating power production, these renewables are incapable of providing reliable base load power. To enable the transition to a renewable energy system, large-scale energy storage is required to compensate for short-term and seasonal imbalances and to save temporary excess power. Due to the order of magnitude involved, this can best be achieved by converting electricity into hydrogen via electrolysis, a process that is also called "power to gas". Hereby, hydrogen can serve as a link combining the electricity, traffic and heating sector into one energy market. This paper presents the process chains of different power-to-gas paths, including different transformation technologies, which it evaluates with regard to their suitability for applications, the optional methanation step including the necessary production of CO 2 , distribution options and geological storage options as well as end-user applications. Finally, the use of hydrogen and methane in transportation and reconversion to power are compared from the economic point of view.

Fariba Safizadeh | Edward Ghali | Georges Houlachi

© 2014 Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. This review provides an overview of some important investigations performed on the development of efficient electrocatalysts in the presence of alkaline solutions. The efficient electrocatalysts must encounter different characteristics such as low overpotential for hydrogen evolution reaction (HER), good catalytic activity, high stability and low cost. This review provides basic information, particularly about the development and properties of some of the most investigated electrocatalysts, namely from the iron group elements (iron, nickel or cobalt). A great interest to investigate a morphous alloys can be found in literature because of their superior properties towards HER. Amorphous alloys show many interesting properties such as electrochemical and good mechanical properties along with high corrosion resistance. Molybdenum and phosphorous, as most promising elements offering great amorphization capability, were widely investigated in the literature. The induced co-deposition of molybdenum and phosphorous was particularly considered in this review. Other metal groups such as pure metals, some rare-earth elements etc. were also discussed as alloyed composites. A focus was made on electrodeposition method used for the alloys preparation, especially for chlor-alkali industry applications.

Nurhidayatullaili Muhd Julkapli | Samira Bagheri

© 2014 Hydrogen Energy Publications, LLC. The unique properties of two-dimensional structure, great intrinsic carrier, well developed porosity, active surface area, outstanding electronic properties and promising mechanical and thermal stability make graphene as the current support key material in the heterogeneous catalyst system. Accordingly, graphene plays a pivotal role in most heterogeneous catalysts ranging from single to bi-functional, hybrid, oxide and nano systems. This combination also inspires and widens the heterogeneous catalyst application areas, including chemical conversion, photocatalyst, electrochemical sensor, fuel cell, energy storage and others. This review highlights the advantages and limitations of carbon materials as catalyst support materials, addresses recent progress on synthesis routes with technological advances in the characterization of graphene, and follows the properties dependent of graphene as a superior catalyst support material.

Paul E. Dodds | Iain Staffell | Adam D. Hawkes | Francis Li | Philipp Grünewald | Will McDowall | Paul Ekins

Copyright © 2014, The Authors. Published by Elsevier Ltd on behalf of Hydrogen Energy Publications, LLC. The debate on low-carbon heat in Europe has become focused on a narrow range of technological options and has largely neglected hydrogen and fuel cell technologies, despite these receiving strong support towards commercialisation in Asia. This review examines the potential benefits of these technologies across different markets, particularly the current state of development and performance of fuel cell micro-CHP. Fuel cells offer some important benefits over other low-carbon heating technologies, and steady cost reductions through innovation are bringing fuel cells close to commercialisation in several countries. Moreover, fuel cells offer wider energy system benefits for high-latitude countries with peak electricity demands in winter. Hydrogen is a zero-carbon alternative to natural gas, which could be particularly valuable for those countries with extensive natural gas distribution networks, but many national energy system models examine neither hydrogen nor fuel cells for heating. There is a need to include hydrogen and fuel cell heating technologies in future scenario analyses, and for policymakers to take into account the full value of the potential contribution of hydrogen and fuel cells to low-carbon energy systems.

Anirban Kundu | Jaya Narayan Sahu | Ghufran Redzwan | M. A. Hashim

Bio-electrohydrogenesis through Microbial Electrolysis Cell (MEC) is one of the promising technologies for generating hydrogen from wastewater through degradation of organic waste by microbes. While microbial activity occurs at anode, hydrogen gas is evolved at the cathode. Identifying a highly efficient and low cost cathode is very important for practical implication of MEC. In this review, we have summarized the efforts of different research groups to develop different types of efficient and low cost cathodes or cathode catalysts for hydrogen generation. Among all the materials used, stainless steel, Ni alloys Pd nanoparticle decorated cathode are worth mentioning and have very good efficiency. Industrial application of MEC should consider a balance of availability and efficiency of the cathode material. © 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Yu Chuan Lin

Glycerol, a byproduct derived from the production of biodiesel, is currently in an oversupply crisis worldwide. One approach to alleviate this problem is to transform glycerol into valuable chemicals such as hydrogen and syngas. Pyrolysis, steam reforming, partial oxidation, autothermal reforming, and aqueous-phase reforming are promising routes for the catalytic conversion of glycerol. However, certain challenges are still limiting their development. Recent advances in catalyst design, reactor engineering, and theoretical chemistry have enabled us to understand glycerol valorization on macro- and microscopic scales, and may help overcome existing thresholds. With the synergistic efforts of these tools, glycerol may no longer be a burden, but a valuable resource of hydrogen and syngas in the near future. Copyright © 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

N. N. Smirnov | V. B. Betelin | R. M. Shagaliev | V. F. Nikitin | I. M. Belyakov | Yu N. Deryuguin | S. V. Aksenov | D. A. Korchazhkin

Computer aided design of new effective and clean hydrogen rocket engines needs mathematical tools for supercomputer modeling of hydrogen-oxygen components mixing and chemically reacting in rocket combustion chambers. The paper presents the results of computer code developing, verification and validation, making it possible to simulate unsteady processes of ignition and combustion of hydrogen fuel in rocket engines. Restrictions on unsteady gas dynamics working cycles supercomputer simulations due to accumulations of errors are developed. © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Canan Acar | Ibrahim Dincer

In this study, we present a comparative environmental impact assessment of possible hydrogen production methods from renewable and non-renewable sources with a special emphasis on their application in Turkey. It is aimed to study and compare the performances of hydrogen production methods and assess their economic, social and environmental impacts, The methods considered in this study are natural gas steam reforming, coal gasification, water electrolysis via wind and solar energies, biomass gasification, thermochemical water splitting with a Cu-Cl and S-I cycles, and high temperature electrolysis. Environmental impacts (global warming potential, GWP and acidification potential, AP), production costs, energy and exergy efficiencies of these eight methods are compared. Furthermore, the relationship between plant capacity and hydrogen production capital cost is studied. The social cost of carbon concept is used to present the relations between environmental impacts and economic factors. The results indicate that thermochemical water splitting with the Cu-Cl and S-I cycles become more environmentally benign than the other traditional methods in terms of emissions. The options with wind, solar and high temperature electrolysis also provide environmentally attractive results. Electrolysis methods are found to be least attractive when production costs are considered. Therefore, increasing the efficiencies and hence decreasing the costs of hydrogen production from solar and wind electrolysis bring them forefront as potential options. The energy and exergy efficiency comparison study indicates the advantages of biomass gasification over other methods. Overall rankings show that thermochemical Cu-Cl and S-I cycles are primarily promising candidates to produce hydrogen in an environmentally benign and cost-effective way. Copyright © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

W. Y. Wong | W. R.W. Daud | A. B. Mohamad | A. A.H. Kadhum | K. S. Loh | E. H. Majlan

The emergence of fuel cell technology has created a new tool for the generation of clean, high efficiency alternative energy for humans. The research and development of new catalysts to replace the expensive and rare platinum (Pt) to reduce the overall cost of fuel cells is ongoing in this area. Nitrogen-doped carbon and its composites possess great potential for fuel cell catalyst applications especially at the oxygen reduction cathode. It is proposed that the reaction mechanisms of nitrogen-doped carbon catalysts for oxygen reduction involve adsorption of oxygen at the partially polarised carbon atoms adjacent to the nitrogen dopants, different from the mechanism at platinum catalysts, which utilise d-bands filling at oxygen adsorption sites. Nitrogen doping in both carbon nanostructures and its composites with active metals or ceramics are reviewed. Nitrogen-doped carbon without composite metals, displays high catalytic activity in alkaline fuel cells and exhibits significant activity in proton exchange membrane fuel cells and direct methanol fuel cells. Pt-based catalysts with nitrogen-doped carbon supports show enhanced catalytic activity towards oxygen reduction, attributed to the enhanced anchoring of Pt to the support that results in better dispersion and stability of the electrodes. For nitrogen-doped carbon composites with non-noble metals (Fe, Co, etc), enhanced activity is seen in both proton exchange and alkaline fuel cells. There are many ongoing debates about the nature of nitrogen-carbon bond in catalysis. Pyrrole- and pyridinic-type nitrogen generally considered to be responsible for the catalytic sites in acidic and alkaline media, respectively. In recent years, significant efforts have been made towards increasing the stability of nitrogen-doped carbon catalysts in acidic media through the formation of composites with ceramic or metal oxide materials. This article reviews the progress in the area of this new class of catalysts and their composites for greater enhancement of oxygen reduction activity and stability in various fuel cell applications. Copyright © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Helton José Alves | Cícero Bley Junior | Rafael Rick Niklevicz | Elisandro Pires Frigo | Michelle Sato Frigo | Carlos Henrique Coimbra-Araújo

Several factors have led to growing interest in a hydrogen energy economy, especially for transportation. A successful transition to a major role for hydrogen will require much greater cost-effectiveness, fueling infrastructure, consumer acceptance, and a strategy for its basis in renewable energy feedstocks. Despite modest attention to the need for a sustainable hydrogen energy system in several countries, in most cases in the short to mid term hydrogen will be produced from fossil fuels. This paper surveys the global status of hydrogen energy research and development (R&D) and public policy, along with the likely energy mix for making it. The current state of hydrogen energy R&D among auto, energy and fuel-cell companies is also briefly reviewed. Just two major auto companies and two nations have specific targets and timetables for hydrogen fuel cells or vehicle production, although the EU also has an aggressive, less specific strategy. Iceland and Brazil are the only nations where renewable energy feedstocks are envisioned as the major or sole future source of hydrogen. None of these plans, however, are very certain. Thus, serious questions about the sustainability of a hydrogen economy can be raised.

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