Regenerative fuel cell

Last updated

A regenerative fuel cell or reverse fuel cell (RFC) is a fuel cell run in reverse mode, which consumes electricity and chemical B to produce chemical A. By definition, the process of any fuel cell could be reversed. [1] However, a given device is usually optimized for operating in one mode and may not be built in such a way that it can be operated backwards. Standard fuel cells operated backwards generally do not make very efficient systems unless they are purpose-built to do so as with high-pressure electrolysers, [2] regenerative fuel cells, solid-oxide electrolyser cells and unitized regenerative fuel cells. [3]

Contents

Process description

A hydrogen fueled proton-exchange membrane fuel cell, for example, uses hydrogen gas (H2) and oxygen (O2) to produce electricity and water (H2O); a regenerative hydrogen fuel cell uses electricity and water to produce hydrogen and oxygen. [4] [5] [6]

When the fuel cell is operated in regenerative mode, the anode for the electricity production mode (fuel cell mode) becomes the cathode in the hydrogen generation mode (reverse fuel cell mode), and vice versa. When an external voltage is applied, water at the anode side will undergo electrolysis to form oxygen and protons; protons will be transported through the solid electrolyte to the cathode where they can be reduced to form hydrogen. In this reverse mode, the polarity of the cell is opposite to that for the fuel cell mode. The following reactions describe the chemical process in the hydrogen generation mode:

At cathode: H2O + 2e− → H2 + O2−

At anode: O2− → 1/2O2 + 2e−

Overall: H2O → 1/2O2 + H2

Solid oxide regenerative fuel cell

One example of RFC is solid oxide regenerative fuel cell. Solid oxide fuel cell operates at high temperatures with high fuel-to-electricity conversion ratios and it is a good candidate for high temperature electrolysis. [7] Less electricity is required for electrolysis process in solid oxide regenerative fuel cells (SORFC) due to high temperature.

The electrolyte can be O2− conducting and/or proton (H+) conducting. The state of the art for O2− conducting yttria stabilized zirconia (YSZ) based SORFC using Ni–YSZ as the hydrogen electrode and LSM (or LSM–YSZ) as the oxygen electrode has been actively studied. [7] Dönitz and Erdle reported on the operation of YSZ electrolyte cells with current densities of 0.3 A cm−2 and 100% Faraday efficiency at only 1.07 V. [8] The recent study by researchers from Sweden shows that ceria-based composite electrolytes, where both proton and oxide ion conductions exist, produce high current output for fuel cell operation and high hydrogen output for electrolysis operation. [9] Zirconia doped with scandia and ceria (10Sc1CeSZ) is also investigated as potential electrolyte in SORFC for hydrogen production at intermediate temperatures (500-750 °C). It is reported that 10Sc1CeSZ shows good behavior and produces high current densities, with suitable electrodes. [10]

Current density–voltage (j-V) curves and impedance spectra are investigated and recorded. Impedance spectra are realized applying an ac current of 1–2A RMS (root-mean-square) in the frequency range from 30 kHz to 10−1 Hz. Impedance spectra shows that the resistance is high at low frequencies (<10 kHz) and near zero at high frequencies (>10 kHz). [11] Since high frequency corresponds to electrolyte activities, while low frequencies corresponds to electrodes process, it can be deduced that only a small fraction of the overall resistance is from the electrolyte and most resistance comes from anode and cathode. Hence, developing high performance electrodes are essential for high efficiency SORFC. Area specific resistance can be obtained from the slope of j-V curve. Commonly used/tested electrodes materials are nickel/zirconia cermet (Ni/YSZ) and lanthanum-substituted strontium titanate/ceria composite for SORFC cathode, and lanthanum strontium manganite (LSM) for SORFC anode. Other anode materials can be lanthanum strontium ferrite (LSF), lanthanum strontium copper ferrite and lanthanum strontium cobalt ferrite. Studies show that Ni/YSZ electrode was less active in reverse fuel cell operation than in fuel cell operation, and this can be attributed to a diffusion-limited process in the electrolysis direction, or its susceptibility to aging in a high-steam environment, primarily due to coarsening of nickel particles. [12] Therefore, alternative materials such as the titanate/ceria composite (La0.35Sr0.65TiO3–Ce0.5La0.5O2−δ) or (La0.75Sr0.25)0.95Mn0.5Cr0.5O3 (LSCM) have been proposed electrolysis cathodes. Both LSF and LSM/YSZ are reported as good anode candidates for electrolysis mode. [13] Furthermore, higher operation temperature and higher absolute humidity ratio can result in lower area specific resistance. [14]

See also

Related Research Articles

<span class="mw-page-title-main">Electrochemical cell</span> Electro-chemical device

An electrochemical cell is a device that generates electrical energy from chemical reactions. Electrical energy can also be applied to these cells to cause chemical reactions to occur. Electrochemical cells that generate an electric current are called voltaic or galvanic cells and those that generate chemical reactions, via electrolysis for example, are called electrolytic cells.

<span class="mw-page-title-main">Fuel cell</span> Device that converts the chemical energy from a fuel into electricity

A fuel cell is an electrochemical cell that converts the chemical energy of a fuel and an oxidizing agent into electricity through a pair of redox reactions. Fuel cells are different from most batteries in requiring a continuous source of fuel and oxygen to sustain the chemical reaction, whereas in a battery the chemical energy usually comes from substances that are already present in the battery. Fuel cells can produce electricity continuously for as long as fuel and oxygen are supplied.

<span class="mw-page-title-main">Electrolysis</span> Technique in chemistry and manufacturing

In chemistry and manufacturing, electrolysis is a technique that uses direct electric current (DC) to drive an otherwise non-spontaneous chemical reaction. Electrolysis is commercially important as a stage in the separation of elements from naturally occurring sources such as ores using an electrolytic cell. The voltage that is needed for electrolysis to occur is called the decomposition potential. The word "lysis" means to separate or break, so in terms, electrolysis would mean "breakdown via electricity."

<span class="mw-page-title-main">Solid oxide fuel cell</span> Fuel cell that produces electricity by oxidization

A solid oxide fuel cell is an electrochemical conversion device that produces electricity directly from oxidizing a fuel. Fuel cells are characterized by their electrolyte material; the SOFC has a solid oxide or ceramic electrolyte.

<span class="mw-page-title-main">Alkaline fuel cell</span> Type of fuel cell

The alkaline fuel cell (AFC), also known as the Bacon fuel cell after its British inventor, Francis Thomas Bacon, is one of the most developed fuel cell technologies. Alkaline fuel cells consume hydrogen and pure oxygen, to produce potable water, heat, and electricity. They are among the most efficient fuel cells, having the potential to reach 70%.

<span class="mw-page-title-main">High-temperature electrolysis</span> Technique for producing hydrogen from water

High-temperature electrolysis is a technology for producing hydrogen from water at high temperatures or other products, such as iron or carbon nanomaterials, as higher energy lowers needed electricity to split molecules and opens up new, potentially better electrolytes like molten salts or hydroxides. Unlike electrolysis at room temperature, HTE operates at elevated temperature ranges depending on the thermal capacity of the material. Because of the detrimental effects of burning fossil fuels on humans and the environment, HTE has become a necessary alternative and efficient method by which hydrogen can be prepared on a large scale and used as fuel. The vision of HTE is to move towards decarbonization in all economic sectors. The material requirements for this process are: the heat source, the electrodes, the electrolyte, the electrolyzer membrane, and the source of electricity.

A proton-exchange membrane, or polymer-electrolyte membrane (PEM), is a semipermeable membrane generally made from ionomers and designed to conduct protons while acting as an electronic insulator and reactant barrier, e.g. to oxygen and hydrogen gas. This is their essential function when incorporated into a membrane electrode assembly (MEA) of a proton-exchange membrane fuel cell or of a proton-exchange membrane electrolyser: separation of reactants and transport of protons while blocking a direct electronic pathway through the membrane.

<span class="mw-page-title-main">Electrolysis of water</span> Electricity-induced chemical reaction

Electrolysis of water is using electricity to split water into oxygen and hydrogen gas by electrolysis. Hydrogen gas released in this way can be used as hydrogen fuel, but must be kept apart from the oxygen as the mixture would be extremely explosive. Separately pressurised into convenient 'tanks' or 'gas bottles', hydrogen can be used for oxyhydrogen welding and other applications, as the hydrogen / oxygen flame can reach approximately 2,800°C.

<span class="mw-page-title-main">Fast-ion conductor</span>

In materials science, fast ion conductors are solid conductors with highly mobile ions. These materials are important in the area of solid state ionics, and are also known as solid electrolytes and superionic conductors. These materials are useful in batteries and various sensors. Fast ion conductors are used primarily in solid oxide fuel cells. As solid electrolytes they allow the movement of ions without the need for a liquid or soft membrane separating the electrodes. The phenomenon relies on the hopping of ions through an otherwise rigid crystal structure.

Lanthanum strontium cobalt ferrite (LSCF), also called lanthanum strontium cobaltite ferrite is a specific ceramic oxide derived from lanthanum cobaltite of the ferrite group. It is a phase containing lanthanum(III) oxide, strontium oxide, cobalt oxide and iron oxide with the formula La
xSr
1-xCo
yFe
1-yO
3, where 0.1≤x≤0.4 and 0.2≤y≤0.8.

<span class="mw-page-title-main">Lanthanum strontium manganite</span>

Lanthanum strontium manganite (LSM or LSMO) is an oxide ceramic material with the general formula La1−xSrxMnO3, where x describes the doping level.

Genoa Joint Laboratories (GJL) is a scientific research activity founded in 2002, combining expertise in electroceramics and electrochemistry of three facilities: National Research Council - Institute for Energetics and Interphases (CNR-IENI), Department of Chemical and Process Engineering with University of Genova (DICHeP), and the Department of Chemistry and Industrial Chemistry with University of Genova (DCCI), all located in Genoa, Italy.

The Glossary of fuel cell terms lists the definitions of many terms used within the fuel cell industry. The terms in this fuel cell glossary may be used by fuel cell industry associations, in education material and fuel cell codes and standards to name but a few.

<span class="mw-page-title-main">Solid oxide electrolyzer cell</span> Type of fuel cell

A solid oxide electrolyzer cell (SOEC) is a solid oxide fuel cell that runs in regenerative mode to achieve the electrolysis of water by using a solid oxide, or ceramic, electrolyte to produce hydrogen gas and oxygen. The production of pure hydrogen is compelling because it is a clean fuel that can be stored, making it a potential alternative to batteries, methane, and other energy sources. Electrolysis is currently the most promising method of hydrogen production from water due to high efficiency of conversion and relatively low required energy input when compared to thermochemical and photocatalytic methods.

<span class="mw-page-title-main">Alkaline anion-exchange membrane fuel cell</span>

An alkaline anion-exchange membrane fuel cell (AAEMFC), also known as anion-exchange membrane fuel cells (AEMFCs), alkaline membrane fuel cells (AMFCs), hydroxide-exchange membrane fuel cells (HEMFCs), or solid alkaline fuel cells (SAFCs) is a type of alkaline fuel cell that uses an anion-exchange membrane to separate the anode and cathode compartments.

<span class="mw-page-title-main">Proton exchange membrane electrolysis</span> Technology for splitting water molecules

Proton exchange membrane(PEM) electrolysis is the electrolysis of water in a cell equipped with a solid polymer electrolyte (SPE) that is responsible for the conduction of protons, separation of product gases, and electrical insulation of the electrodes. The PEM electrolyzer was introduced to overcome the issues of partial load, low current density, and low pressure operation currently plaguing the alkaline electrolyzer. It involves a proton-exchange membrane.

Gadolinium-doped ceria (GDC) (known alternatively as gadolinia-doped ceria, gadolinium-doped cerium oxide (GCO), cerium-gadolinium oxide (CGO), or cerium(IV) oxide, gadolinium-doped, formula Gd:CeO2) is a ceramic electrolyte used in solid oxide fuel cells (SOFCs). It has a cubic structure and a density of around 7.2 g/cm3 in its oxidised form. It is one of a class of ceria-doped electrolytes with higher ionic conductivity and lower operating temperatures (<700 °C) than those of yttria-stabilized zirconia, the material most commonly used in SOFCs. Because YSZ requires operating temperatures of 800–1000 °C to achieve maximal ionic conductivity, the associated energy and costs make GDC a more optimal (even "irreplaceable", according to researchers from the Fraunhofer Society) material for commercially viable SOFCs.

<span class="mw-page-title-main">Mars Oxygen ISRU Experiment</span> Mars 2020 electrochemical experiment

The Mars Oxygen In-Situ Resource Utilization Experiment (MOXIE) was a technology demonstration on the NASA Mars 2020 rover Perseverance investigating the production of oxygen on Mars. On April 20, 2021, MOXIE produced oxygen from carbon dioxide in the Martian atmosphere by using solid oxide electrolysis. This was the first experimental extraction of a natural resource from another planet for human use. The technology may be scaled up for use in a human mission to the planet to provide breathable oxygen, oxidizer, and propellant; water may also be produced by combining the produced oxygen with hydrogen.

<span class="mw-page-title-main">Mixed conductor</span>

Mixed conductors, also known as mixed ion-electron conductors(MIEC), are a single-phase material that has significant conduction ionically and electronically. Due to the mixed conduction, a formally neutral species can transport in a solid and therefore mass storage and redistribution are enabled. Mixed conductors are well known in conjugation with high-temperature superconductivity and are able to capacitate rapid solid-state reactions.

<span class="mw-page-title-main">Reversible solid oxide cell</span>

A reversible solid oxide cell (rSOC) is a solid-state electrochemical device that is operated alternatively as a solid oxide fuel cell (SOFC) and a solid oxide electrolysis cell (SOEC). Similarly to SOFCs, rSOCs are made of a dense electrolyte sandwiched between two porous electrodes. Their operating temperature ranges from 600°C to 900°C, hence they benefit from enhanced kinetics of the reactions and increased efficiency with respect to low-temperature electrochemical technologies.

References

  1. ↑ "Reversible fuel cell learning kit". Ecosoul.org. Archived from the original on May 11, 2008. Retrieved 2009-09-24.
  2. ↑ "2001-High pressure electrolysis – The key technology for efficient H.2" (PDF). Retrieved 2009-09-24.[ permanent dead link ]
  3. ↑ "Microsoft Word - E-14264 Layout.doc" (PDF). Archived from the original (PDF) on 2009-06-29. Retrieved 2009-09-24.
  4. ↑ "Electrolyzer and Reversible Fuel Cell". Nfcrc.uci.edu. Archived from the original on 2009-06-18. Retrieved 2009-09-24.
  5. ↑ "Proton Exchange Membrane- based Electrochemical Hygrogen Generator". European Commission. 2005-10-01. Retrieved 2021-10-18.
  6. ↑ "Hydrogen-oxygen PEM regenerative fuel cell" (PDF). Archived from the original (PDF) on 2011-03-03. Retrieved 2009-09-24.
  7. 1 2 Laguna-Bercero, M. A.; Campana, R.; Larrea, A.; Kilner, J. A.; Orera, V. M. (30 July 2010). "Performance and Aging ofMicrotubular YSZ-based Solid Oxide Regenerative Fuel Cells" (PDF). Fuel Cells. 11: 116–123. doi:10.1002/fuce.201000069. hdl: 10261/53668 . S2CID   33333495.
  8. ↑ Dönitz, W.; Erdle, E. (1985). "High-temperature electrolysis of water vapor—status of development and perspectives for application". International Journal of Hydrogen Energy. 10 (5): 291–295. doi:10.1016/0360-3199(85)90181-8.
  9. ↑ zhu, Bin; Ingvar Albinsson; Camilla Andersson; Karin Borsand; Monika Nilsson; Bengt-Erik Mellander (20 February 2006). "Electrolysis studies based on ceria-based composites". Electrochemistry Communications. 8 (3): 495–498. doi:10.1016/j.elecom.2006.01.011.
  10. ↑ Laguna-Bercero, M.A; S.J. Skinnera; J.A. Kilner (1 July 2009). "Performance of solid oxide electrolysis cells based on scandia stabilised zirconia" (PDF). Journal of Power Sources. 192 (1): 126–131. Bibcode:2009JPS...192..126L. doi:10.1016/j.jpowsour.2008.12.139. hdl: 10044/1/13889 .
  11. ↑ Brisse, Annabelle; Josef Schefold; Mohsine Zahida (October 2008). "High temperature water electrolysis in solid oxide cells". International Journal of Hydrogen Energy. 33 (20): 5375–5382. doi:10.1016/j.ijhydene.2008.07.120.
  12. ↑ Marina, O. A.; Pederson, L. R.; Williams, M. C.; Coffey, G. W.; Meinhardt, K. D.; Nguyen, C. D.; Thomsen, E. C. (22 March 2007). "Electrode Performance in Reversible Solid Oxide Fuel Cells" (PDF). Journal of the Electrochemical Society. 154 (5): B452. Bibcode:2007JElS..154B.452M. doi:10.1149/1.2710209.
  13. ↑ Laguna-Bercero, M.A.; J.A. Kilner; S.J. Skinner (2011). "Development of oxygen electrodes for reversible solid oxide fuel cells with scandia stabilized zirconia electrolytes". Solid State Ionics. 192: 501–504. doi:10.1016/j.ssi.2010.01.003.
  14. ↑ Hauch, A.; S. H. Jensen; S. Ramousse; M. Mogensen (18 July 2006). "Performance and Durability of Solid Oxide Electrolysis Cells". Journal of the Electrochemical Society. 153 (9): A1741. Bibcode:2006JElS..153A1741H. doi:10.1149/1.2216562. S2CID   98331744.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.