Electrochemistry – Fuel Cell

A fuel cell is an electric power generating technology that makes use of electrochemical reactions. It can generate electricity by persuading independent electrodes coupled to an external circuit to oxidise hydrogen generated by recovering natural gas or other fuels, as well as a reaction to reduce oxygen in the air. The main reaction is frequently defined as the polar opposite of water electrolysis. This is due to the electrochemical reaction that produces electric power and water from hydrogen and oxygen. In actuality, water produced during energy generation is used for ordinary everyday activities within the space vehicle in the case of fuel cells employed in space vehicles.

Different kinds of fuel cells

Fuel cells of many sorts have been produced. Because the electrolyte dictates the operational temperature of a system and, in essence, the type of fuel that could be utilised, they are normally categorised based on the electrolyte utilised.

Fuel cells with polymer electrolyte membrane

Polymer electrolyte membrane (PEM) fuel cells, also known as proton exchange membrane fuel cells, have a high power density and therefore are lighter and smaller than that of 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.

PEM fuel cells run at 80 °C (176 °F), which is a comparatively low temperature. Low-temperature operation enables them to start quicker (with shorter warm-up time) and reduces wear on system components, resulting in greater durability. This reactor is also more expensive.

USES: PEM fuel cells are most commonly employed in transportation and some permanent purposes. Vehicle applications, including cars, buses, and heavy-duty vehicles, are especially suited to PEM fuel cells.

Cells for direct Methanol Fuel

The majority of fuel cells run on hydrogen, which can be delivered directly into the system or created inside the unit by reforming hydrogen-rich fuels like methanol, ethanol, and hydrocarbon fuels. Pure methanol, which itself is commonly combined with water and shipped straight to the fuel cell anode, is used in direct methanol fuel cells (DMFCs).

As methanol has a higher efficiency than hydrogen—though not as high as gasoline or diesel fuel—direct methanol fuel cells avoid the many fuel storage issues that plague other fuel cell systems. Since it is a liquid, like gasoline, methanol is also convenient to carry and deliver to the public utilising our current infrastructure.

USES:- DMFCs are frequently used to power portable fuel cell devices like cell phones and laptop computers.

Cells for alkaline fuel

Alkaline fuel cells (AFCs) were among the earliest fuel cell technologies to be invented, and they were the first form of fuel cell frequently applied in the United States space programme to create 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. Innovative AFCs with a polymer membrane as the electrolyte have already been greatly developed. Such fuel cells are similar to traditional PEM fuel cells, except instead of an acid membrane, they have used an alkaline membrane. The great efficiency of AFCs is attributed to the fast rate of electrochemical reactions in the cell. 

Fuel cells for phosphoric acid

Liquid phosphoric acid is used as the electrolyte in phosphoric acid fuel cells (PAFCs), which are housed in a Teflon-bonded silicon carbide matrix with porous carbon electrodes and a platinum catalyst as electrodes. In the picture to the right, the electrochemical reactions that occur in the cells are depicted.

Modern fuel cells are classified as “first generation” by the PAFC. It is among the most developed cell kinds, as well as the first to be commercialised. Although PAFCs are primarily used only for stationary power generation, they have also been utilised to power big vehicles, including city buses.

As a result, these fuel cells are often bulky and heavy. PAFCs are also costly. They require far more pricey platinum catalyst loadings than that of other forms of fuel cells, which drives up the price.

Carbonate fuel cells with molten carbonate

For electrical utility, industrial, and military uses, molten carbonate fuel cells (MCFCs) are continually being made for natural gas and coal-based power plants. MCFCs are high-temperature fuel cells which use a molten carbonate salt combination contained in a porous, chemically inert ceramic lithium aluminium oxide matrix as an electrolyte. Non-precious metals can be employed as catalysts at the anode and cathode since they work at high temperatures of 650 °C (approximately 1,200 °F), lowering expenses.

Cells for solid oxide fuel

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 converter to the system.

Fuel cells that can be used in both the directions

Reversible fuel cells, like conventional fuel cells, produce electricity from hydrogen and oxygen while also generating heat and water as byproducts. Reversible fuel cell systems, on the other hand, can divide water into oxygen and hydrogen fuel using electricity from solar, wind, or other sources. This process is known as electrolysis. Reversible fuel cells can produce electricity when needed, but they can also store extra energy in the form of hydrogen during periods of high power production from other technologies (such as when high winds result in an excess of available wind power). 

Conclusion

Fuel cells are a promising technology that has the potential to play a significant part in the transition away from fossil fuels. More research and development can be done to address these technological issues. Fuel cells, despite their lengthy history, have received far less investment than batteries or combustion engines, and hence are a considerably less established technology