Modeling of electrocatalytic hydrogen evolution via high voltage alkaline electrolyzer with different nano-electrocatalysts
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Alkaline water electrolysis
Electrolysis of water
Thermal energy
Chemical energy
High-pressure electrolysis
The importance of hydrogen as a fuel will steadily increase in future, mainly due to environmental necessities. Water electrolysis is the only proven technology for hydrogen production from nonfossil fuel primary energy sources. R& D on water electrolysis have been done to improve cell performance in efficiency and operating current density, since the energy crisis of 1973. Significant improvements have been made possible and further improvements are anticipated.This paper summarizes the design features of the following three major advanced electrolyzers the advanced alkaline water electrolyzer, the solid polymer electrolyte water electrolyzer and the high temperature water vapor electrolyzer.
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Abstract To test commercially available water electrolysis systems under dynamic (close‐to‐real) operation a test area with three different electrolyzers is build up, covering the significant technologies alkaline water electrolysis, proton exchange membrane water electrolysis, and high temperature steam electrolysis using solid oxide electrolysis cells. The hydrogen outputs of the systems are in the range between 5 to 10 Nm 3 h −1 hydrogen at delivery pressures between 10 and 35 bar. Additional balance of plant is installed to demonstrate and evaluate the utilization of hydrogen for different applications.
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High-pressure electrolysis
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Abstract With the impending unavailability of oil and natural gas, hydrogen will be produced on a large scale in the United States (1) from coal, or (2) by water electrolysis using electricity derived from nuclear or solar energy. In many parts of the world which lack fossil fuels, the latter will be the only possible method. The cost of purification of hydrogen produced from fossil fuels will increase its cost to about the same level as that of electrolytic hydrogen. When hydrogen is required in relatively small quantities too, the electrolytic method is advantageous. To minimize the cost of hydrogen produced by water electrolysis, it is necessary to reduce capital costs and approach 100% energy efficiencies. Areas of research, which will be necessary to achieve these goals are: (1) maximization of surface areas of electrodes; (2) use of thin electrolyte layers; (3) increase of operating temperature in alkaline water electrolysis cells to about 120–150°C; (4) selection and evaluation of separator materials; (5) electrocatalysis of the hydrogen and oxygen electrode reaction; (6) mixed oxides as oxygen electrodes; and (7) photoelectrochemical effects. The progress made to date and proposed studies on these topics are briefly dealt with in this paper. The General Electric Solid Polymer Water Electrolyzer and Teledyne Alkaline Water Electrolysis Cells, operating at about 120–150°C, look most promising in achieving the goals of low capital cost and high energy efficiency.
Alkaline water electrolysis
High Temperature Electrolysis
Electrolysis of water
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High-pressure electrolysis
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Polymer electrolyte membrane (PEM) fuel cells are an attractive energy conversion device because of the potential for extremely high efficiency and low emissions. Hydrogen is an ideal fuel for PEM fuel cells but it is energy intensive to produce. Currently the main method of producing hydrogen is steam reforming of natural gas. This is a break from the renewable energy future promised by hydrogen fuel cells. The most obvious method of producing hydrogen is water electrolysis but that is highly energy intensive since the electrolysis requires greater than the theoretical voltage of 1.23 V and thus is somewhat inefficient. To fulfill the promise of fuel cells, less energy intensive methods of producing hydrogen must be found. Here we describe some initial exploration of the concept of replacing water in the anode electrolyzer feed with a feedstock from which hydrogen can be stripped and purified in a combined electrochemical reactor. As a first step in testing this concept, we use methanol as the feed. Oxidation of methanol to hydrogen takes place at a theoretical voltage of .03 V. This is a significantly lower over-potential than water electrolysis and since most of the operating cost is energy, it has the potential to be significantly cheaper. Of course, the methanol oxidation reaction requires substantial overpotential because of sluggish kinetics but this is only an initial study. We constructed a methanol water electrolyzer based the conventional direct methanol fuel cell architecture as shown in Figure 1. The electrolysis cell uses a Pt-Ru black catalyst in the anode and a Pt cathode with a Nafion 117 membrane. We examined the effects of several different catalyst loadings, back-pressures, temperatures, and humidity levels. Finally, we utilized electrochemical impedance spectroscopy (EIS) and a dynamic hydrogen electrode (DHE) to more accurately determine the effectiveness of the catalysis and sources of voltage loss. Figure 2 shows an initial polarization curve obtained with this cell. Hydrogen was chosen for the working electrode and methanol for the counter electrode. The counter electrode potential stays fairly steady as does the ASR, while the working and cell potentials depend somewhat on the current being drawn. Increasing polarization of the working electrode begins to have a negative effect on cell current after .6V vs DHE. Acknowledgements We gratefully acknowledge the support of the Office of Naval Research for this activity. References C. Cloutier and D. Wilkinson, International Journal of Hydrogen Energy., 35,9,(2010) S. Thomas, X. Ren, S. Gottesfeld and P. Zelenay, Electrochimica Acta., 47 (2002)
High-pressure electrolysis
Electrolysis of water
High Temperature Electrolysis
Methanol reformer
Overpotential
Power-to-Gas
Direct-ethanol fuel cell
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Hydrogen produced by water electrolysis could be cost effective over the merchant hydrogen used for generator cooling. Advanced water electrolyzers are being developed specifically for this utility application. These designs are based on solid-polymer-electrolyte and alkaline water electrolysis technologies. This paper describes the status of electrolyzer development and demonstration projects.
High-pressure electrolysis
Electrolysis of water
Alkaline water electrolysis
High Temperature Electrolysis
Electrolytic cell
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Alkaline water electrolysis
High Temperature Electrolysis
Power-to-Gas
Electrolysis of water
High-pressure electrolysis
Energy carrier
Capital cost
Separator (oil production)
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Hydrogen is a promising energy vector for the future. Among the different methods of its production, the electrolysis of water has attracted great attention because it is a sustainable and renewable chemical technology. Thus, hydrogen represents a suitable energy vector for the storage of intermittent energies. This chapter is devoted to the hydrogen generation by water electrolysis as an important part of both existing and emerging industrial electrochemical processes. It aims to give an insight into the theoretical foundations of the operating principles of different types of electrolyzers. Also, it is developed in this chapter, the thermodynamic and kinetic aspects of the reactions taking place at the electrodes of water electrolysis. The evolution reaction of hydrogen has a rapid kinetics, and thus, the polarization of the cathode is not critical. On the other hand, the evolution reaction of oxygen is characterized by a very slow kinetics and is thus responsible for most of the overvoltage in the electrolysis of water. The most important technologies of water electrolysis are addressed: alkaline electrolysis, proton exchange membrane electrolysis, and solid oxide high-temperature electrolysis.
Electrolysis of water
High-pressure electrolysis
Alkaline water electrolysis
High Temperature Electrolysis
Power-to-Gas
Oxygen evolution
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Water electrolysis is accepted as direct method for hydrogen production from water. The emission pathway of hydrogen is related to the source of electric energy and process of water electrolysis just define energy efficiency or amount of hydrogen produced from energy supplied. For green hydrogen production almost exclusively, renewable energy sources are necessary. But unstable production is typical for most frequently mentioned wind and solar power station. Currently four types of water electrolyzers are available: Proton exchange membrane water electrolysis (PEMWE), Alkaline water electrolysis (AWE), Membrane alkaline water electrolysis (MAWE) and high temperature solid oxide water electrolysis (SOWE). Each of mentioned type exhibits different properties and requirements if operated in combination with renewable power sources. Proper selection of electrolyzer type and its size is crucial for economic production of hydrogen. PEMWE shows higher flexibility in operation changes. Its warming up to operating temperature is only few minutes or seconds due to the high current densities, thin ion conductive membrane and circulation only of demineralized water. Its production range is limited by hydrogen permeation through membrane at low production and electrolyzer stability at high production. The production range starts usually from 5% and finish at short term 120% of designed capacity. AWE represents oldest technology with high durability proved by large number of installations. But old electrolysers were designed for continual operation with limited possibility to moderate its production. Newly developed units are better adapted to intermittent operation. Parasitic currents in electrolyte distribution channels are main reason for efficiency decrease at low loading. Their minimum operation range varies from 1% up to 30% depending of manufacturer and size. Despite it, the request for circulation of concentrated hydroxide and low conductivity of separator make warm up period significantly slower with low efficiency. Therefore, frequent phase off and on affect the total amount of produced hydrogen. MAWE is newest electrolyzer type. It combines the concept of ion selective membrane usage as separator and alkaline environment to avoid platinum metals need. Thanks to the ion-selective membrane the startup dynamics is faster but durability of membrane limits its operation temperature. SOWE as process with operating temperature 800 °C is not suitable for irregular operation. But it high efficiency make this process interesting for combination of power sources to keep permanent run. Nuclear and renewable power sources are one of possible combination. Mathematical model capable to calculate actual and integral production of hydrogen on the base of known power sources production and elektrolyzer parameters was created. Input data of elektrolyzer behavior for the model come from an in-house measurement and from literature. Various data of for unstable power sources involve a photovoltaic power-plant and train recuperation energy from braking on the 15 min interval were taken. Created model indicates production capacity of given combination and also the running time and amount of utilized energy. With consideration of investment cost i tis able to estimate most suitable sizes. Acknowledgment: This project is financed by the Technology Agency of the Czech Republic under grant TO01000324, in the frame of the KAPPA programme, with funding from EEA Grants and Norway Grants.
High-pressure electrolysis
Electrolysis of water
Alkaline water electrolysis
Electrolytic process
High Temperature Electrolysis
Power-to-Gas
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Alkaline water electrolysis is the one of technologies of hydrogen production through decomposition of water by an electric power. The present study aims at improvement of hydrogen production in 'water electrolysis from viewpoint of generated bubbles' behavior, which interrupts the electric current between two electrodes. The measurement of electric current and the visualization of bubbly flow are practiced simultaneously to discuss the influence of the two-phase flow structure onto the water electrolysis. The paper describes two experiments on the micro-channel water electrolysis and on the water electrolysis by use of vibrating electrodes.
Electrolysis of water
Alkaline water electrolysis
High Temperature Electrolysis
High-pressure electrolysis
Electric current
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High-pressure electrolysis
Electrolysis of water
Alkaline water electrolysis
Power-to-Gas
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