A hydrogen fuel cell is a clean energy system which uses hydrogen fuel to produce electricity, with water as a by-product. It works by combining hydrogen and oxygen atoms in an electrochemical reaction, thereby converting chemical energy to electric power. This article discusses the hydrogen fuel cell definition, history, parts and principle; according to the following outline;
Hydrogen Fuel Cell Definition: 6 Ways to Define the Hydrogen Fuel Cell
A hydrogen fuel cell is a technology that depends on hydrogen as an energy source, to produce electricity.
It is important to consider the energy source used in a hydrogen fuel cell, because this factor is what distinguishes it from other fuel cells.
Generally, a fuel cell is a technological unit which uses chemical energy from a source (or fuel) to produce electricity in a clean and efficient way . For hydrogen fuel cells, the energy source is hydrogen.
Another factor that can be used to define a hydrogen fuel cell, is the energy conversion that takes place in this cell;
A hydrogen fuel cell is an electrochemical cell, which actively converts chemical energy to electricity, through a clean and efficient process.
As the above definition points out, the production of electricity by a hydrogen fuel cell occurs as a result of chemical reactions and energy conversion. This can be considered when defining a hydrogen fuel cell;
A hydrogen fuel cell is a cell in which hydrogen and oxygen atoms combine in a series of electrochemical redox reactions, leading to the flow of electrons and the generation of electricity, with pure water as a by-product.
Given that the only notable by product of electricity generation in a hydrogen fuel cell is water, it is convenient to describe it as a clean mechanism for producing electric power, as elaborated below;
A hydrogen fuel cell is an electricity-generation technology that produces electric power from chemical energy, in a clean and efficient process.
The above definition implies that the hydrogen fuel cell may be an applicable means of addressing environmental degradation, global warming and climate change problems that are related to energy consumption and electricity generation.
Considering that hydrogen is the fuel used in this type of energy cell, it is important to define the hydrogen fuel cell in terms of the potential sources of hydrogen fuel;
A hydrogen fuel cell is an energy technology which generates electricity from hydrogen fuel, which may be derived from both renewable and nonrenewable natural resources, including radioactive nuclides (nuclear sources), natural gas, biomass, wind and solar energy.
Lastly, hydrogen fuel cells can be defined on the basis of their similarity to energy-storage batteries;
A hydrogen fuel cell is an energy cell that works like an electric battery , by utilizing electrochemical reactions to generate electricity from chemical energy and electron flow.
History and Origin of The Hydrogen Fuel Cell
The concept of the hydrogen fuel cell can be traced back to the year 1800, when Anthony Carlisle and William Nicholson, provided a description of the process by which electricity can be used to break down water, to yield hydrogen and oxygen .
However, the first know practical use of hydrogen fuel cell technology is attributed to the Welsh inventor William Robert Grove; who demonstrated the working principle of the cell in 1839 .
Grove’s model of the hydrogen fuel cell, comprised of platinum and zinc electrodes immersed in nitric acid and zinc sulfate respectively, and was called the “gas battery” and the “Grove cell”.
The Grove cell generated electricity, but in very small amounts.
Charles Langer and Ludwig Mond, are credited with coining the term “fuel cell” in 1889 .
This achievement was based on experiments which they performed with platinum electrodes and coal-derived gas.
The model by Mond and Langer produced more electricity than that of William Grove. This marked an improvement, and influenced further research on the topic.
Baltic German chemist Wilhelm Ostwald performed a series of experiments in 1893, which helped to determine the functions and relevance of components of the fuel cell .
These experiments were the basis of subsequent modifications to the model of the hydrogen fuel cell.
Charles Thompson and Charles Alder Wright developed a fuel cell model in the late nineteenth century.
While this model by Thompson and Wright was similar in operational mechanism, to that of Mond ad Langer, they documented some of its practical limitations, such as poor containment of gases and (resultant) low power production.
Based on the electrochemical principles of the fuel cell, William W. Jacques constructed a power cell called the “carbon battery” in the year 1896 .
The cell comprised of an alkali which served as the electrolyte, and in which electrochemical reaction occurred in the presence of oxygen.
Experiments conducted by Swiss scientist Emil Baur in the early 1900s, addressed the role of electrodes, electrolytes, and physicochemical conditions, on the performance of fuel cells .
This dimension of analysis used by Baur, is arguably the same which led to the adoption of the hydrogen fuel cell as a prominent type of electrochemical power cell.
The 1920s saw further research that led to the introduction of modified fuel cell principles, such as those behind the design of the solid oxide fuel cell.
Francis Bacon researched extensively into fuel cell technology .
His studies, which lasted between 1932 and 1959, led to notable improvement of the performance of the fuel cell in terms of reliability and power output.
Bacon also defined the hydrogen fuel cell as an efficient model by showing that the model was less expensive and more effective than other fuel cells.
In the 1940s, Soviet chemist O. K. Davtyan, performed experiments that were instrumental toward the development of improved-electrolyte fuel cells like the Molten Carbonate Fuel Cell (MCFC).
The late 1950s and the 1960s, saw the use of fuel cells in the automobile industry.
This commenced with the demonstration of a fuel cell-powered tractor by Harry Karl Ihrig of the Allis-Chalmers Company in 1959 .
Application of the fuel cell in the space technology field commenced in the early 1960s, with the construction of the first fuel cell-driven power system for space capsules, by General Electric .
Specifically, the hydrogen fuel cell model was used for these projects, based on earlier studies carried out by Bacon.
The end of the twentieth century was marked by an increase in the adoption of the hydrogen fuel cell as a viable electricity generation technology, with the demonstration of fuel cell-powered vehicles in the 1990s.
A similar trend has occurred since the turn of the twenty-first century.
Parts of A Hydrogen Fuel Cell
The main parts of a hydrogen fuel cell are;
- Gas Diffusion Layers
- Fuel (Hydrogen)
1). The Anode
In a hydrogen fuel cell, the anode is (electrically) negative, because of the significant accumulation of electrons on the surface of the anode, compared to the cathode.
In conventional electrochemical cells and batteries, the anode is the positive electrode . Here, oxidation occurs, as electrons are lost, and transferred to the cathode, at which reduction (electron-gain) occurs.
At the anode in a hydrogen fuel cell, oxidation occurs. However, the electrons produced are usually excessive, hence, the anode is negatively charged.
The anode of a hydrogen fuel cell acts as a catalyst for the breakdown of the hydrogen fuel. It is usually composed of platinum, platinum-based alloy, or platinum-coated metal.
When hydrogen fuel is introduced into the fuel cell, it is supplied to the anode, at which it is broken down to yield electrons and protons, as shown in the following reaction;
Anodic half reaction:
2H2(g) + 4OH-(aq) > 4H2O(l) + 4e- ___(1)
The electrons are usually produced in large numbers, and surround the anode, thereby giving it a highly-negative charge. These electrons are transferred to the cathode, to complete the electrolytic reaction.
2). The Cathode
In a hydrogen fuel cell, the cathode is positively charged with respect to the anode.
This is because the cathode usually has less electrons accumulated on its surface at any given time, than the anode.
In some cases, the cathode may be composed of platinum-coated material or platinum alloy.
These materials act as a catalyst for the reduction of oxygen to produce water.
Oxygen is usually supplied to the cathode, where it reacts with the hydrogen ions (protons), and electrons which were produced in the electrolytic reaction at the anode.
The main product of this reaction is water.
Cathodic half reaction:
O2(g) + 2H2O(l) + 4e- > 4OH-(aq) ___(2)
Overall hydrogen fuel cell electrolytic reaction:
2H2(g) + O2(g) > 2H2O(l) —(3)
An alkali is generally used as electrolyte in a hydrogen fuel cell, because of the ability of hydroxyl ions (OH-) to act as proton carriers from the anode to the cathode, thereby facilitating the generation of electric current through the cell.
In many cases, the alkali electrolyte is potassium hydroxide (KOH).
A membrane material (called a polymer electrolyte membrane) can act as the electrolyte in a hydrogen fuel cell.
This material is designed to actively conduct protons, while limiting the transmission of electrons . The result is an accumulation of un-transmitted electrons around the anode, thereby giving it a negative charge.
4). Gas Diffusion Layers
In a hydrogen fuel cell, the gas diffusion layer (GDL) is an important component which helps to manage the transport of gas and water within the cell .
It is used in proton exchange membrane (PEM) fuel cells, where a membrane serves as the electrolyte.
There are various forms in which the gas diffusion layers can occur. Generally, they are composed of fibrous, porous materials , where carbon is often a primary constituent.
The electrodes/catalysts, membrane and gas diffusion layers in a hydrogen fuel cell combine to form the membrane electrode assembly (MEA) .
In a hydrogen fuel cell, the fuel is usually gaseous or liquid hydrogen.
Due to the low energy density of hydrogen, is can be stored as a highly compressed gas or a cryogenic liquid .
It is important to note that in a hydrogen fuel cell, the hydrogen fuel is not ‘burnt’ or made to undergo combustion, but is rather put through electrolytic reactions that result in electricity generation.
Also, it is believed that the use of hydrogen in a fuel cell does not produce any significant greenhouse gas emissions . For this reason, hydrogen fuel cell technology is viewed as a clean potential solution to energy problems.
Aside the five main components described above, other components of the hydrogen fuel cell include gaskets and bipolar plates , which are part of the membrane electrolyte assembly (MEA).
How Does A Hydrogen Fuel Cell Work?
A hydrogen fuel cell works in a series of four steps, which are; hydrogen introduction, hydrogen dissociation, electron propagation, and water formation.
These steps are discussed below;
1). Hydrogen Introduction
Hydrogen is introduced at the anode of a hydrogen fuel cell .
The physical characteristics of the hydrogen fuel used in a fuel cell, depend on the working principle of the cell and the required attributes to work efficiently.
Hydrogen fuel may be introduced either as a gas, or as a liquid.
2). Hydrogen Dissociation
In this second step, the hydrogen fuel is broken down to produce positively-charged hydrogen ions and negatively-charged electrons.
In order to facilitate the oxidation and ionization of hydrogen, the cathode is usually plated with, or composed of platinum, which acts as a catalyst.
3). Electron Propagation
The protons and electrons produced from the oxidation of hydrogen, are propagated through different pathways in the hydrogen fuel cell.
For the electrons, they are transmitted through an external circuit, thereby producing electricity from current-flow. Heat is often a by-product of this conversion of chemical energy to electric power.
The protons (hydrogen ions) migrate through the electrolyte or porous membrane, to the cathode .
4). Water Formation
When the protons reach the cathode in a hydrogen fuel cell, they react with oxygen and electrons to form molecules of water .
The oxygen involved in this reaction is introduced at the cathode, and the reaction is also driven catalysts, which may be platinum or nickel, among others.
Because water is the sole product of the electrochemical process in a hydrogen fuel cell, the cell is considered a clean energy technology.
Is The Hydrogen Fuel Cell a Renewable or Nonrenewable Technology?
The hydrogen fuel cell is not a renewable energy, because most of the sources of hydrogen fuel which is used in the cell, are nonrenewable.
Hydrogen does not exist freely as a native element therefore it cannot be accessed without limits. Rather, it must be derived from other resources. This is why the hydrogen fuel cell is not a renewable technology.
However, there is a bit of confusion as to whether a hydrogen fuel cell is renewable or nonrenewable. This is because the sources from which hydrogen can be derived, include renewable and nonrenewable resources.
Renewable natural resources from which hydrogen fuel can be derived include;
Nonrenewable natural resources which can be used as sources of hydrogen fuel include;
- Natural gas
- Radioactive Materials
Although hydrogen fuel cell is not a renewable technology, it is clean and environment-friendly, since the main product of the electricity generation process is water.
A hydrogen fuel cell is an electricity generation unit which oxidizes hydrogen fuel to produce electric power, with water a by-product.
The five main parts or components of a hydrogen fuel cell are;
- The Anode
- The Cathode
- Gas Diffusion Layers
A hydrogen fuel cell works based on four main steps, which are;
- Hydrogen Introduction
- Hydrogen Dissociation
- Electron Propagation
- Water Formation
Although the hydrogen fuel cell is not a renewable technology, it can be powered by hydrogen fuel derived from both renewable and nonrenewable sources, such as petroleum, natural gas, biomass, solar, wind and geothermal energy.
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