Fuel Cells

Some of the most advanced technologies ever created derive their power from something so insignificant in comparison to them. As a result, grasping the entire technology at one sitting becomes difficult. Cells and batteries are an example of such inventions. While we have discussed cells in general in previous sections, we will focus on fuel cells in this one.

A fuel cell is a small device that uses a chemical reaction to generate electricity. It generates electricity when two electrodes are present. In 1839, Sir William Grove developed the first fuel cell. He just believed that if electricity could divide water into hydrogen and oxygen, then reversing the process would yield the opposite outcome.

Introducing Fuel Cells

A fuel cell is an electrochemical cell that creates electrical energy from fuel through an electrochemical process. These cells require a constant fuel supply and an oxidizing agent to maintain the reactions that generate electricity (generally oxygen). As a result, these cells will continue to create electricity even if their fuel and oxygen supplies are turned off. 

A fuel cell is similar to an electrochemical cell in that it has a cathode, an anode, and an electrolyte. In these cells, the electrolyte allows protons to move about.

A hydrogen-powered generator differs from batteries in that it requires an uninterruptible/continuous supply of fuel as well as oxygen to keep its chemical reaction alive and well. The chemicals placed in batteries, on the other hand, react continually to generate electricity. In a nutshell, a fuel cell can continue to produce electricity as long as the reactants are available, whereas batteries eventually run out of power.

In the early 1840s, a fuel cell was discovered. NASA utilized a commercial fuel cell to launch space shuttles for the first time. Fuel cells are being employed as a power backup for industries, commercial dwellings, and even some vehicles, such as motorbikes, submarines, and boats, as well as forklifts.

How Do Fuel Cells Work? 

The reaction between hydrogen and oxygen can be used to generate power in a fuel cell. Such a hydrogen-oxygen fuel cell was utilized in the Apollo space program and fulfilled two main purposes: as a supply of fuel and as a drinking water source. 

This hydrogen-oxygen fuel cell worked by transferring hydrogen and oxygen into a concentrated sodium hydroxide solution via carbon electrodes. The cells’ response can be written as follows:

• Cathode Reaction – O2 + 2H2O + 4e– → 4OH–

• Anode Reaction – 2H2 + 4OH– → 4H2O + 4e–

• Net Cell Reaction – 2H2 + O2 → 2H2O

This electrochemical response, on the other hand, has a slow reaction rate. This difficulty can be solved by using a catalyst such as platinum or palladium. Before being inserted into the electrodes, the catalyst is finely split.

Different Kinds Of Fuel Cells

Fuel cells come in a variety of shapes and sizes, even though they all work in the same way. In this part, we’ll look at a few of these fuel cell kinds.

– Polymer Electrolyte Membrane (PEM) Fuel Cell:

Polymer electrolyte membrane (PEM) fuel cells, also known as proton exchange membrane fuel cells, have a high power density and are lighter and smaller than other fuel cells. A solid polymer electrolyte and porous carbon electrodes with a platinum or platinum alloy catalyst are used in PEM fuel cells. 

To function, they simply require hydrogen, oxygen from the air, and water. Pure hydrogen from storage tanks or reformers is usually used to power them.

– Phosphoric Acid Fuel Cell

The electrolyte of phosphoric acid fuel cells (PAFCs) is liquid phosphoric acid, which is housed in a Teflon-bonded silicon carbide matrix, while the electrodes are porous carbon electrodes with a platinum catalyst. In the diagram to the right, the electrochemical reactions that occur in the cell are depicted. 

Modern fuel cells are classified as “first generation” by the PAFC. It is one of the most developed cell kinds, as well as the first to be commercialized. Although PACs are primarily used for stationary power generation, they have also been utilized to power big vehicles such as city buses.

– Alkaline Fuel Cell

Alkaline fuel cells (AFCs) were one of the earliest fuel cell technologies to be invented. They were the first form of fuel cell widely employed in the United States space program to produce electrical energy and water on-board spacecraft. 

The electrolyte in these fuel cells is a solution of potassium hydroxide in water, and the anode and cathode can be made of a variety of non-precious metals. 

Novel AFCs with a polymer membrane as the electrolyte have been developed in recent years. These fuel cells are similar to traditional PEM fuel cells, except instead of an acid membrane, they use an alkaline membrane.

– Solid Oxide Fuel Cell

The electrolyte of solid oxide fuel cells (SOFCs) is a hard, non-porous ceramic composition. The efficiency of SOFCs in converting fuel to electricity is roughly 60%. Overall fuel consumption efficiency could reach 85 percent in systems that capture and use the system’s waste heat (cogeneration). 

SOFCs operate at extremely high temperatures, up to 1,000 degrees Celsius (1,830 degrees Fahrenheit). The use of a high-temperature operation eliminates the requirement for a precious-metal catalyst, lowering costs. It also allows SOFCs to reform fuels internally, allowing them to use a wider range of fuels while lowering the expense of adding a reformer to the system.

– Molten Carbonate Fuel Cell

For electrical utility, industrial, and military uses, molten carbonate fuel cells (MCFCs) are currently being developed for natural gas and coal-based power plants. MCFCs are high-temperature fuel cells that use an electrolyte made up of molten carbonate salts floating in a porous, chemically inert ceramic lithium aluminum oxide matrix as an electrolyte.

Non-precious metals can be used as catalysts at the anode and cathode because they operate at high temperatures of 650°C (roughly 1,200°F). This saves money.

Working of HOFC

At Anode:

H2 gas is injected into the anode. The platinum layer on the anode acts as a catalyst, assisting in the conversion of hydrogen to hydrogen cations and free electrons. Because the passage of electrons produces electricity, this free electron goes from anode to cathode across the entire connected circuit and gives power to the bulb/load connected to the circuit.

Anodic reaction: 2H2 → 4H+ + 4e−

The Oxidation Reaction is named after the loss of electrons at the anode. 

At Cathode:

The H+ ion produced at the anode travels through the electrolyte to reach the cathode. The oxygen at the cathode combines with electrons from the anode and the H+ ion to produce heat and water, which is then expelled from the cell.

Cathodic Reaction: O2 + 4H+ + 4e− → 2H2O + Heat

The Reduction reaction is named as electrons are acquired at the cathode.

The Benefits of Using Fuel Cells 

– Hydrogen and oxygen, the reactants of a hydrogen-oxygen fuel cell, are readily available. 

– It does not pollute the environment. 

– It is safe for the environment. 

– It is used to power rockets. 

– This gasoline is quite effective. 

– A hydrogen fuel cell is a renewable energy source. 

– Because low-temperature fuel cells release less heat, they can be used in military applications. 

– It has a longer operating period than batteries; therefore, it can save a country time and money. 

The Drawbacks Of Using Fuel Cells

– The process of manufacturing is costly. 

– A hydrogen oxygen fuel cell is difficult to keep track of. 

– It is extremely flammable. 

– It relies on fossil fuels to keep it separate from nature. 

– A hydrogen fuel cell can’t hold a large amount of fuel at once. 

– It releases nitrogen dioxide into the atmosphere.

Conclusion

To summarise, fuel cells are a viable technology that has the ability to play a significant part in the transition away from fossil fuels.

The benefits of hydrogen fuel cells as one of the finest renewable energy sources are obvious. However, there are still a number of obstacles to overcome before hydrogen can fully realise its promise as a crucial facilitator for a future decarbonized energy system.

Hydrogen could be the best option for our future energy needs, but it will take political determination and investment to make it happen. However, when fossil fuels become scarce, hydrogen fuel cells may become an important source of energy for the world’s population.