Have you ever thought that the water that you use to drink or clean can be used to power an entire vehicle? Neither have I.
Well, not until this point.
More than half of our world is made of water, and this water can be used to provide electricity for the light bulbs in your house or even provide energy for your car. It’s not a complicated process, but there are a few electrochemical reactions that occur within the fuel cell. But above all, a huge benefit to using a hydrogen fuel cell to produce electricity is that the only substance you’ll need is water.
To actually use a fuel cell (a device that can produce electricity through chemical reaction) is to supply it with water. After certain processes, the fuel cell will release the same amount of water given. Not to mention, but clean water 💧.
Hydrogen Fuel Cells and batteries have very similar properties but the only difference between them is that batteries work for a limited amount of time. Whereas, fuel cells function as long as fuel is supplied. This means that a hydrogen fuel cell can work as long as water is supplied and fuel cells do NOT degrade.
Just a bit of chemistry background, Hydrogen is a gaseous non-metal element that has an atomic mass 1 dalton and an ionic charge of 1+ (number of electrons: 1). Hydrogen is one of the diatomic molecules, meaning that its molecules are composed of 2 hydrogen atoms. We engage with hydrogen on a daily basis — for instance, the element can be found in water, or even the sugar in your coffee. The most common forms of hydrogen is stored in ammonia, methane, hydrogen peroxide and hydrochloric acid.
Each one of these example consist of a different hydrogen isotope, which make the material what it is. Isotopes are atoms of the same element that have the same number of protons/electrons, but different number of neutrons. There are 3 different hydrogen isotopes: Protium, Deuterium, and Tritium.
- Protium: 1 electron, 1 proton, 0 neutron (original form of hydrogen)
- Deuterium: 1 electron, 1 proton, 1 neutron (commonly known as heavy water)
- Tritium: 1 proton, 1 electron and 2 neutrons
As one of the forms listed above, 99.9% of methane contains protium whereas tritium is artificially made and it’s radioactive. This isotope can be created in nuclear reactors during a reaction between thermal neutrons and lithium.
Deuterium and Tritium is are fuel that are used in nuclear (fission/fusion) reactions, since they produce a helium nucleus and releases an energetic neutrons. However, protium, which is the original form of hydrogen, is used for hydrogen fuel cells to produce electricity.
As I said before, hydrogen can be found in water, and 71% of the world is made of water, which can be used to fuel millions of cars over the world. Fuel cells are devices that produce electricity, and have very similar aspects of a battery. They have the same components, but the only difference is that batteries function for a limited time period, whereas fuel cells, produce electricity has long as fuel is supplied.
A fuel cell generates electricity through an electrochemical reaction, which is a process of deriving electrical energy from redox reactions. Redox reactions is short-term for Oxidation-Reduction Reactions which describes the transfer of electrons in a reaction. Oxidation Reactions are chemical reactions in which oxygen is added and/or hydrogen is removed from a compound. Meanwhile, Reduction reactions are the opposite of oxidation, meaning an element or compound gains electrons.
- Electrochemical Reaction: induces an electrical current and a chemical reaction
- Oxidation: Loss of Electrons
- Reduction: Gain of Electrons
In a Hydrogen Fuel Cell, the hydrogen atoms oxidizes into individual protons and electrons. Hydrogen (diatomic) oxidizes at the platinum catalyst near the anode (negative electrode). Meanwhile, oxygen undergoes reduction at the cathode, since it combines with oxygen to produce water.
Hydrogen Fuel Cells are made of components that have certain properties to generate and product electricity
Like every single machine in the world, there are certain components that play a role in a functioning hydrogen fuel cell. As compounds travel throughout a fuel cell, it interacts with quite a few materials. The 4 main sections of a fuel cell are: Polymer-Electrolyte Membrane, Gas Diffusion Layers, Catalysts, and Electrodes.
Overview of the 5 Main Components in a Fuel Cell:
- Anode: A type of electrode which has a negative charge
- Cathode: A type of electrode which has a positive charge
- Electrolyte: An electrically conducting compound/solution dissolved in a neutral substance and has the ability to conduct ions between electrodes. In a battery, electrolytes transfers positive ions. This is a material is essential to induce an electric current.
- Catalyst: A material that increases the rate of a chemical reaction, but doesn’t alter or can’t be consumed during a reaction
Starting off with one of the most important materials needed for a hydrogen fuel cell is the Polymer-Electrolyte Membrane which is also known as PEMs. These are materials that are normally found at the very middle of a fuel cell, and consists of hydrogen ions (positively-charged: protons) due to chemical reactions of decomposition. There are a number of hydrogen fuel cells, which depends on the material of the membrane. Hydrogen membranes are normally composed of Polymer — specifically; perfluorosulfonic-acid-type ion exchange membrane such as Nafion. Nafion has a molecular structure of polytetrafluoroethylene chain with side chains containing sulfonic acid which tend to operate at temperatures below 90 Celsius, and have a high ionic conductivity property. This means that these substances are designed to transfer certain ions, usually positive charged ions (in this case, hydrogen protons)
- Nafion: a sulfonated tetrafluoroethylene based fluoropolymer-copolymer
On both sides of the PEMs, resides two distinctive gas diffusion layers. Gas Diffusion Layers (GDLs) are located between the catalysts and the PEM. These layers have the ability to facilitate transport of reactants and products between sections of the fuel cell. The GDLs on either side are composed of carbon paper, with carbon fibers coated in polytetrafluoroethylene (PTFE). Gases, such as hydrogen or oxygen, diffuse through these layers since there are pores which are held open by hydrophobic PTFE (prevents water-buildup). The inner layers of the GDLs consists of carbon mixed with PFTE (microporous layer). Maintaining conductivity, and gas/water levels are essential for the function of a fuel cell which is conducted by the microporous layers.
Before gases enter the PEM and Diffusion layers, substances engage with catalyst, that have the ability to increase the rate of reaction and separate compounds of molecules needed for a reaction. For example, hydrogen is separated into subatomic particles and is directed to other components of the fuel cell. There are 2 catalyst found in a cell, in each electrode. The first type is the platinum catalyst that plays a role in dividing hydrogen diatomic molecules into electron and protons. Whereas, the second type is a nickel catalyst, that combined protons (H+) with electrons to recreate hydrogen molecules. Each catalyst is found near the electrodes of a fuel cell which can be classified into 2 categories: Anode and Cathodes.
Anodes have an overall charge of negative, whereas cathodes have an overall positive charge. Anodes tend to push electrons into a current, therefore a half-reaction known as oxidation occurs. On the complete opposite side of the fuel cell, lies the cathode. The cathode allows electrons to enter, allowing the half-reaction reduction to occur.
The anode and cathode are interconnected electrodes, since the anode provides the cathode with electrons to attract specific elements in the solution contained in the fuel cell. These terms are normally used to explain process such as electrolysis.
Electrolysis is a process in which compounds are separated by electricity. For example, a galvanic cell with solutions zinc sulphate and copper sulphate, can separate zinc and copper by electrolysis.
Brief Overview of Galvanic Cell (Zinc Sulphate + Copper Sulphate)
Both solutions are divided by a porous disk, and the process begins with a Zinc Anode (negative charge) transfers the 2 electrons per atom into the anode and through a load such as a light bulb. Between each solution, is a salt bridge or semi-permeable membrane that prevents the ions of the more noble metal from plating out at the other electrode.
Once the electron reach the copper cathode, the cathode transfers the electrons to the copper, since copper (II) requires 2 electrons for stability.
Hydrogen fuel cells experience electrolysis when implemented in vehicles or automobiles. For instance, in hydrogen cars, power is needed for electrolysis to occur which can be supplied by several energy sources, such as solar power, wind power, or even batteries. By providing power for a fuel cell, water, the main source of hydrogen, is separated into hydrogen ions, electrons and oxygen gas.
As hydrogen enters a cell into the anode catalyst, it is split into oxygen gas, hydrogen ions (protons), and electrons. The electrons along with the protons travel to the cathode and become hydrogen gas when combined, meanwhile oxygen gas exits the anode for storage.
When the vehicle is in use, the process occurs but just in reverse!
Hydrogen gas is brought into the fuel cell, and is separated into 2 electrons and 2 protons that are transferred to the anode, and combines to oxygen gas to form water, and is taken out of the fuel cell.
Note that during discharge the cathode is positive and the anode is negative. However, during charge the anode is positive, and the cathode is negative. In this case, when the fuel cell is being powered by energy sources, the anode becomes positive — allowing hydrogen to move from anode to cathode. When the vehicle is working on its own, the process is reversed since hydrogen diatomic molecules move from cathode to anode.
So, how does this all relate to a hydrogen fuel cell?
The process begins with hydrogen as a diatomic molecules entering the anode of a fuel cell and into a gas diffusion layer (GDL) which is a porous layer composed of carbon. The catalyst the anode of a fuel cell, which is made of a platinum powder, decomposes the hydrogen atoms, and into 1 proton and electron.
The hydrogen protons travel through the electrolyte which transfers the protons to the cathode section. There are several different types of electrolyte with distinct materials. In most hydrogen fuel cells, polymer electrolyte membrane (PEM) are used, and for this reason, they are called PEM Fuel Cell. The electrolyte conducts the protons to the cathode catalyst, which is normally made of nickel and converts the ions into waste chemicals.
Since particles of an atom always aim to achieve stability, negative particles tend to be attracted to positive particles. Therefore, the electrons travel to the cathode by the help of a circuit, since they can’t travel through the electrolyte (which is specifically designed to transport protons).
The circuit is connected to a load, for instance a light bulb, and as the electrons pass through the circuit, it produces an electric current or (flow of electron) which provides electricity for the light bulb.
After the electrons have passed through the light bulb, it travels to the nickel catalyst in the cathode. The electrons are attracted to the protons because of its electronegativity, and this produces the atom hydrogen (1 proton + 1 electron). At the same time, oxygen gas (diatomic molecule) enters the cathode and passes through the gas diffusion layer. As the molecule splits into individual atoms, the nickel catalyst combines the 1 oxygen atom (charge of -1) with 2 hydrogen atoms (each have a charge of -1) in a process known as covalent bonding.
- Covalent Bonding: A bond between two non-metals that share an electron instead of transferring. Elements aim to have full valence shells (Full shells: 2 electrons in the first shell or 8 electrons in the last shell of an element)
The bond of oxygen and 2 hydrogen atoms in a fuel cell create the compound water, making it the product of the reaction. Since there is a combination of elements, in this case ~ oxygen and hydrogen, 110 kilojoules per mole of energy (in the form of heat) is produced.
There are two types of reactions involving heat: Exothermic and Endothermic
- Exothermic: reactions that release energy (Ex. Combustion reactions such as burning a candle)
- Endothermic: reaction that absorb energy (Ex. photosynthesis)
The binding of oxygen and hydrogen in fuel cells is an example of exothermic reactions, and this can be proven since the reaction exhausts heat. Therefore the products of a fuel cell are water and heat.
Along with substances that contribute to chemical reactions in a fuel cell, there are hardware components required to power the MEA (Membrane Electrode Assembly) which where electrochemical reactions. All these parts of a fuel cell listed above (is part of the MEA, and hardware components are needed to enable energy efficiency — which includes; Biopolar plates & Gaskets
- Biopolar Plates
In a regular hydrogen fuel cell, around 1 V of energy is produced, therefore cells are stacked together to produce higher amounts of energy. Fuel cells have individual chemical reactions, This is possible since each cell in a stack are placed between two bipolar plates to separate it from the other cells. Bipolar Plates are normally made of metal, carbon or any material that has the ability to conduct electricity between cells, by allowing electrons or ions to travel through flow fields. These flow fields look very much like tunnels, and the materials that travel across can act like trains. Bipolar plates support the fuel cell, and are the backbones of each cell.
2. Gaskets
Gaskets are embedded in both sides of a fuel cell, enabling a gas-tight seal to prevent gases or substances from exiting the cell. This is like the security guards of the cell, since it prevents unknown gases to come in or go out. The most usual material used for gaskets are thin layers of rubbery polymer, and have an outlined shape.
In a fuel cell stack, the electricity produced is in the form of DC (direct current), and if the energy needs to be converted to AC (alternate current), there needs to be an inverter. The amount of energy produced depends on the type of cell, size, operation temperature, and pressure of gases. These can be modified by systems in a fuel cell:
- Processor — removes impurities in the fuel
- Power Conditioners — control current, voltage and frequency
- Humidifiers — A thin membrane that keeps the PEM hydrated for it to work (PEM doesn’t work when it is dry)
- Air Compressors — alters pressure of reactant gases (Hydrogen)
The hardest part of the fuel cell doesn’t have much to do with its components or reactions, but instead collecting hydrogen from certain sources.
Hydrogen makes up 14% of the Earth’s Crust
This means that it’s an abundant element, however hydrogen can be combined with other elements to create other products. Our most common contact with hydrogen is water which is a compound of 2 hydrogen atoms and 1 oxygen atom. Hydrogen can be obtained by electrolysis, which is the a recognized method since 72% of earth is covered in water.
In other products such as hydrocarbons, hydrogen can detach from carbons based on the type of product. For instance natural gases like oil have a chemical formula of C8H18 can undergo a Reforming Reactions to produce hydrogen. Reforming reactions such as steam reforming is a type of method that involves separation of hydrocarbons by combining with water to produce hydrogen and carbon oxide (strongly endothermic: absorbs energy in the reaction)
Companies, like shell, have began developing hydrogen vehicles that can use a viable hydrogen source. Shell obtains hydrogen from it’s own oil refinement processes, and uses methods to separate products for hydrogen. Other facilities, such as NASA has been using hydrogen as a source to power space shuttles and aircrafts into space since 1958 which is provided by natural gases in reforming processes. The average cost of hydrogen purchased by Nasa is around $1.65 per gallon.
There’s definitely an opportunity here to use sustainable fuel to power electricity around the world, since approximately 10 million metric tons of hydrogen is produced in the States alone. Whereas globally, 75 million tonnes of pure hydrogen is produced. According to the IEA, it is estimated that there will be a decrease in hydrogen cost of about 30% by 2030. Currently, the cost of hydrogen production can range between $5–7 USD per kg.
In processes involving electrolysis, prices may increase to USD$10–15 per kg. One of the cheapest methods of producing hydrogen is steam methane reforming, in which 50% of the world’s hydrogen is produced at around 700–1100°C and an efficiency of 65–75%.
Hydrogen is a promising source of fuel that can power millions of vehicles and provide electricity from products in a sustainable method. Unlike other energy sources such as solar, wind or nuclear, there are several safety hazard, while other depend on weather condition such as the amount of UV radiation provided (which is inconsistent), and let’s just say it’s not always windy. The point is, hydrogen provides us with energy that is efficient, and doesn’t depend on other factors to produce energy. Believe it or not, but in a couple of years, your own light bulb might be powered from just the water you drink!
Hey, you made it to the end! I’m Sanvi, and I’ve been working on hydrogen as a fuel for automobiles in order to adapt to a sustainable environment. You know what’s a great idea (other than solving climate change) — connecting!
Let’s Connect!
Email: Sanviiraoo@gmail.com
Linkedin: https://www.linkedin.com/in/sanvi-rao/
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