A Study on Hydrogen Fuel Cells Tirth Nagar SCH4U1-3A 01/09/2022 What are Fuel Cells Fuel cells function similarly to batteries, except they do not deplete or require recharging. They continuously generate power and heat if fuel is made available. A fuel cell is a device that produces energy through an electrochemical process rather than combustion. Hydrogen and oxygen are combined in a fuel cell to generate electricity, heat, and water. How do Fuel Cells Work? A fuel cell consists of two electrodes—an anode and a cathode sandwiched around an electrolyte. A fuel, such as hydrogen, is fed to the anode, and oxygen is fed to the cathode. In a hydrogen fuel cell, a catalyst at the anode separates hydrogen molecules into protons and electrons. The electrons go through an external circuit, creating a flow of electricity. The protons migrate through the electrolyte to the cathode, where they unite with oxygen and the electrons to produce water and heat. Properties of the Elements/Compounds Involved in the reaction Hydrogen: Hydrogen is the smallest chemical element because it consists of only one proton in its nucleus. Its symbol is H, and its atomic number is 1 with an average atomic weight of 1.0079 amu it is the lightest element. At standard temperature and pressure, hydrogen is a nontoxic, nonmetallic, odorless, tasteless, colorless, and highly combustible diatomic gas. Hydrogen has one proton and one electron; the most common isotope, protium (1H), has no neutrons. Hydrogen has a melting point of -259.14 °C and a boiling point of -252.87 °C. Hydrogen has a density of 0.08988 g/L, making it less dense than air. It has two distinct oxidation states, (+1, -1), which make it able to act as both an oxidizing and a reducing agent. Oxygen: At STP, two atoms of the element bind to form dioxygen, a colorless, odorless, tasteless diatomic gas with the formula O2. Its symbol is O, and its atomic number is 8 with an average atomic weight of 15.999. The density of oxygen is 1.429 grams per liter. Oxygen is a strong oxidizing agent and has the second-highest electronegativity of all reactive elements. Major classes of structural molecules in living organisms, such as proteins, carbohydrates, and fats, contain oxygen. Oxygen has a melting point of −218.4 °C and a boiling point of −183.0 °C. Water: Water is a liquid at standard temperature and pressure. Water is tasteless and odorless. Water is transparent in the visible part of the electromagnetic spectrum. Water can behave as both an acid and a base. Water is a polar covalent molecule. Water has a specific high heat capacity. It takes a lot of energy to raise the temperature of a certain amount of water by a degree, so water helps with regulating temperature in the environment. Water molecules have strong cohesive forces due to their ability to form hydrogen bonds with one another. Water also has adhesive properties that allow it to stick to substances other than itself. The Chemical Reaction in a Fuel Cell At the Anode… 2H2 → 4H+ + 4e− An Oxidation Reaction Oxidation is a reaction that occurs when there is a loss of electrons or the oxidation state of a molecule, atom, or ion is increased. At the Cathode O2 + 4H+ + 4e− → 2H2O A Reduction Reaction Reduction is a process, which occurs when there is a gain of electrons or the oxidation state of an atom, molecule, or ion decreases. The occurrence of both these reactions simultaneously is known as a redox reaction Environmental Implications of Hydrogen Fuel Cells Hydrogen fuel cells don't pollute the environment, provided that renewable sources are used in the production process. Hydrogen isn't always clean to produce. It's expensive to pull hydrogen from water. Producing hydrogen from non-renewable sources such as oil and natural gas is much cheaper. Ironically, the carbon dioxide released in the process of producing hydrogen from fossil fuels cancels out any benefits to the environment. Emissions of hydrogen can also lead to increased burdens of methane eroding the ozone layer hence contributing to global Warming. Effects of Fuel Cell Technology on Humans The two prime dangers of fuel cells and hydrogen-powered vehicles are the danger of electrical shock and the flammability of the fuel. Many fuel cell vehicle motors run on voltages exceeding 350V which is more than enough to stop a human heart. The second area of concern lies in the fuels used to power this future generation of vehicles. The hydrogen used to power a vehicle does not necessarily have to be stored on the vehicle as hydrogen. Hydrogen stored as such in a vehicle or reformed in it can also be used to power a ‘classic’ internal combustion engine. Besides reforming hydrogen in the vehicle, itself, there are several ways of storing hydrogen in a vehicle. Each has its own set of flammability issues. Effects of Fuel Cell Technology on Humans Fuel cells are typically powered by compressed hydrogen; however, a variety of liquid fuels can be employed with fuel cells. Because the hydrogen must be "Stripped" off the fuel molecule and then utilized in the fuel cell, liquid fuel types may not be as efficient as pure hydrogen depending on the system design. The hydrogen can be stripped from the fuel molecule outside or inside the fuel cell. Methanol, ethanol, and ammonia are among the fuels processed inside the fuel cell. Methanol (CH3OH) is an alcohol-based fuel with a significantly higher energy density than compressed hydrogen. Methanol is an appealing fuel for fuel cells since it is readily available in the supply chain. Approximately 90 percent of the world’s methanol is manufactured from synthesis gas from natural gas. Methanol can also be produced from non-petroleum feedstocks such as coal and biomass. Approximately 75 percent of methanol is used for chemicals, and the remaining 25 percent is used for fuels.
