scholarly journals Micro-kinetic simulations of the catalytic decomposition of hydrazine on the Cu(111) surface

2017 ◽  
Vol 197 ◽  
pp. 41-57 ◽  
Author(s):  
Saeedeh S. Tafreshi ◽  
Alberto Roldan ◽  
Nora H. de Leeuw
Keyword(s):  
Proton Exchange Membrane ◽  
Batch Reactor ◽  
Scale Up ◽  
Catalytic Decomposition ◽  
Proton Exchange ◽  
Decomposition Mechanism ◽  
Power Generators ◽  
Production Of Hydrogen ◽  
Temperature Programmed ◽  
Exchange Membrane

Hydrazine (N2H4) is produced at industrial scale from the partial oxidation of ammonia or urea. The hydrogen content (12.5 wt%) and price of hydrazine make it a good source of hydrogen fuel, which is also easily transportable in the hydrate form, thus enabling the production of H2in situ. N2H4 is currently used as a monopropellant thruster to control and adjust the orbits and altitudes of spacecrafts and satellites; with similar procedures applicable in new carbon-free technologies for power generators, e.g. proton-exchange membrane fuel cells. The N2H4 decomposition is usually catalysed by the expensive Ir/Al2O3 material, but a more affordable catalyst is needed to scale-up the process whilst retaining reaction control. Using a complementary range of computational tools, including newly developed micro-kinetic simulations, we have derived and analysed the N2H4 decomposition mechanism on the Cu(111) surface, where the energetic terms of all states have been corrected by entropic terms. The simulated temperature-programmed reactions have shown how the pre-adsorbed N2H4 coverage and heating rate affect the evolution of products, including NH3, N2 and H2. The batch reactor simulations have revealed that for the scenario of an ideal Cu terrace, a slow but constant production of H2 occurs, 5.4% at a temperature of 350 K, while the discharged NH3 can be recycled into N2H4. These results show that Cu(111) is not suitable for hydrogen production from hydrazine. However, real catalysts are multi-faceted and present defects, where previous work has shown a more favourable N2H4 decomposition mechanism, and, perhaps, the decomposition of NH3 improves the production of hydrogen. As such, further investigation is needed to develop a general picture.

(Invited) Advances in Composite Membranes Design and Scale Up for Proton Exchange Membrane Water Electrolysis

2021 ◽  
Vol MA2021-02 (44) ◽  
pp. 1367-1367
Author(s):  
Alexander Agapov ◽  
Amr Kobaisy ◽  
Christin Wilbert ◽  
Thomas Berta ◽  
Paul Kiernan
Keyword(s):  
Proton Exchange Membrane ◽  
Scale Up ◽  
Water Electrolysis ◽  
Composite Membranes ◽  
Proton Exchange ◽  
Exchange Membrane

scholarly journals Production of Hydrogen and their Use in Proton Exchange Membrane Fuel Cells

2018 ◽  
Author(s):  
Flavio Colmati ◽  
Christian Gonçalves Alonso ◽  
Tatiana Duque Martins ◽  
Roberto Batista de Lima ◽  
Antonio Carlos Chaves Ribeiro ◽  
...  
Keyword(s):  
Fuel Cells ◽  
Proton Exchange Membrane ◽  
Proton Exchange ◽  
Production Of Hydrogen ◽  
Exchange Membrane

scholarly journals Hydrogen Production through a Solar Powered Electrolysis System

2019 ◽  
pp. 1-14
Author(s):  
Deborah A. Udousoro ◽  
Cliff Dansoh
Keyword(s):  
Hydrogen Production ◽  
Proton Exchange Membrane ◽  
Renewable Energy Sources ◽  
Proton Exchange ◽  
Photovoltaic System ◽  
Photovoltaic Module ◽  
Production Of Hydrogen ◽  
Solar Powered ◽  
Exchange Membrane ◽  
Electrolysis System

Production of hydrogen from renewable energy sources is gaining recognition as one of the best energy solutions without ecological drawbacks. The present study reports hydrogen production through a solar powered electrolysis system as a means to curtail greenhouse gas emissions in the United Kingdom. The solar powered electrolysis unit is modeled to provide 58400 kg of hydrogen to run the fuel cell bus fleet in Lea interchange garage in London on a yearly basis. Experiments were conducted to determine the efficiency of the photovoltaic module and the proton exchange membrane electrolyzer. An energy balance of the electrolysis unit was calculated to give 47.82 kWh/kg and used to model a 2.98 MW photovoltaic system required to run the electrolysis process.

Synthesis and Characterization of 20% Pt-Fe/C Alloy as a Cathode Catalyst for Oxygen Reduction Reaction PEMFCs

2012 ◽  
Vol 15 (4) ◽  
pp. 241-247
Author(s):  
Sukmin Kang ◽  
Sungyeol Yoo ◽  
Jina Lee ◽  
Bonghyun Boo ◽  
Bal Chandra Yadav ◽  
...  
Keyword(s):  
Power Systems ◽  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Proton Exchange Membrane ◽  
Electrical Power ◽  
Reduction Reaction ◽  
Proton Exchange ◽  
High Price ◽  
Power Generators ◽  
Exchange Membrane

Proton exchange membrane fuel cells (PEMFCs) are highly efficient and non-polluting electrical power generators based on two electrochemical reactions. Therefore, PEMFCs are considered to be alternative electricity sources for electric vehicles, portable applications and stationary power systems due to their high power density and eco-friendly environment. However, PEMFCs are associated with many problems for their commercialization such as the high price of electrode catalyst and the slow rate of oxygen reduction reaction (ORR). In this study, two different reducing agents NaBH4 and HCHO were used in the synthesis of carbon supported Pt-Fe catalysts (Pt-Fe/C-HCHO and Pt-Fe/C-NaBH4). Both catalysts were characterized using x-ray diffraction (XRD), transmission electron microscopy (TEM) and cyclic voltametry in the range 0.05 -1.2 V vs. SHE. It was observed that reducing agent HCHO is more effective than NaBH4. In order to reduce amount of platinum, the 20% Pt-Fe/C catalyst was prepared by using Fe. The catalysts were heat treated up to 600 °C for improve the activity and stability. It was found that a temperature of 500 °C yielded the best catalyst morphology and ORR activity at 0.9 V.

Development and Diagnosis of a 1-kW Self-Sustainable Proton Exchange Membrane Fuel Cell System With a Methanol Reformer

2013 ◽  
Vol 10 (3) ◽  
Author(s):  
Chen-Yu Chen ◽  
Sui-Wei Hsu ◽  
Wei-Mon Yan ◽  
Wei-Hsiang Lai ◽  
Keng-Pin Huang ◽  
...  
Keyword(s):  
Fuel Cell ◽  
Proton Exchange Membrane ◽  
Performance Test ◽  
Cell System ◽  
Proton Exchange ◽  
Normal Operation ◽  
Peak Power Output ◽  
Fuel Cell System ◽  
Power Generators ◽  
Exchange Membrane

A reformed methanol fuel cell system is one of the most practical of all types of fuel cell systems. It is regarded as one of the best candidates for stationary applications, such as residential power generators, uninterruptible power supply systems, power generators for cell base stations, or power generators in outlying areas. In this research, a 1-kW self-sustainable proton exchange membrane fuel cell system with a methanol reformer is designed and tested. The system performance test and in situ stack monitoring show that the system is stable and reliable. During normal operation, the maximum voltage deviation among the individual cells, which is caused by a nonuniform temperature distribution in the proton exchange membrane fuel cell stack, is 25 mV. The peak power output of the system reaches 1.4 kW. The maximum electrical efficiency is 65.2% at a system power of 1 kW. The system is operated at 1 kW for 4 h, during which the decay rate of the stack power is 0.94%. During the stability test, voltage fluctuation occurs in a certain cell because of a flooding phenomenon. A demonstration is also presented in this paper to show the system’s practicability and commercial potential.

scholarly journals Earth-Abundant Electrocatalysts in Proton Exchange Membrane Electrolyzers

2018 ◽  
Author(s):  
Xinwei Sun ◽  
Kaiqi Xu ◽  
Christian Fleischer ◽  
Xin Liu ◽  
Mathieu Grandcolas ◽  
...  
Keyword(s):  
Noble Metal ◽  
Proton Exchange Membrane ◽  
Water Electrolysis ◽  
Metal Catalysts ◽  
Proton Exchange ◽  
Widespread Application ◽  
Noble Metal Catalysts ◽  
Production Of Hydrogen ◽  
Earth Abundant ◽  
Exchange Membrane

Water electrolysis provides efficient and cost-effective production of hydrogen from renewable energy. Currently, the oxidation half-cell reaction relies on noble-metal catalysts, impeding widespread application. In order to adopt water electrolyzers as the main hydrogen production systems, it is critical to develop inexpensive and earth-abundant catalysts. This review discusses the proton exchange membrane (PEM) water electrolysis (WE) and the progress in replacing the noble-metal catalysts with earth-abundant ones. Researchers within this field are aiming to improve the efficiency and stability of earth-abundant catalysts (EACs), as well as to discover new ones. The latter is particularly important for the oxygen evolution reaction (OER) under acidic media, where the only stable and efficient catalysts are noble-metal oxides, such as IrOx and RuOx. On the other hand, there is significant progress on EACs for the hydrogen evolution reaction (HER) in acidic conditions, but how many of these EACs have been used in PEM WEs and tested under realistic conditions? What is the current status on the development of EACs for the OER? These are the two main questions this review addresses.

Innovative Approach to Leak Detection Solves Several Problems for Plant Operators

2006 ◽  
Author(s):  
John Speranza
Keyword(s):  
Power Plants ◽  
Proton Exchange Membrane ◽  
Proton Exchange ◽  
Innovative Approach ◽  
Power Generators ◽  
Hydrogen Flow ◽  
Large Bulk ◽  
Hydrogen Supply ◽  
Plant Personnel ◽  
Exchange Membrane

Power plants operating hydrogen cooled generators face a few challenges regarding the safe and reliable supply of hydrogen to their electric power generators. The mode of hydrogen supply differs from plant to plant depending on such things as distance from the central hydrogen supply or permit restrictions on the amount of stored hydrogen. There are number of plants that utilize single cylinders or transportable cradles of six, twelve, or eighteen cylinders. Others utilize large bulk systems that are either stationary high or low pressure tanks or transportable high pressure tube trailers. Subsequently the volume of hydrogen on a particular power plant site can vary from a couple hundred cubic feet to over a hundred thousand cubic feet. One of the chief safety concerns that many plant operators are faced with is the possibility that a major generator casing leak or facility piping leak occurs while a large volume of hydrogen is “lined up” to continuously feed hydrogen to the generator. The operator is faced with few options to mitigate this safety risk. One method used to mitigate this risk is to isolate the hydrogen supply and manually feed hydrogen into the generator when monitored closely by plant personnel. Other approaches include the implementation of mass flow meters to monitor the flow of hydrogen and alarm if a prescribed limit is exceeded and excess flow valves that are designed to limit the amount of hydrogen flow going through them. An alternate and innovative approach has been implemented at a handful of power plants recently utilizing a Proton Exchange Membrane (PEM) hydrogen generator. The generator not only makes the hydrogen needed to maintain pressure and purity within the generator casing, but also has the inherent ability to monitor demand and alert plant operators if a hydrogen leak occurs.

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