Compared to gas-powered engines, fuel cells are greener because electricity is produced in these cells without burning up hydrogen (or other fuel) that empowers them. But they cannot be manufactured on a commercial scale because they are very expensive.
Researchers have been successful today in creating a fuel cell, which operates at a midrange temperature. Thus, researchers have developed an inexpensive, powerful version of fuel cells, which boosts chances of developing abundant green energy.
Most fuel cells operate at temperatures, which are either too hot or too cool; therefore, they cannot be manufactured at a reasonable price. Polymer electrolyte membrane (PEM) cells are used to empower cars and buses, which are operated at about 100°C.
Solid oxide fuel cells (SOFCs) provide power backup generators for hospitals and other buildings, and they typically operate at 1000 °C. The essential chemical reactions continue at a sluggish rate when PEM cells are operated at a lower temperature.
Expensive metal catalysts, such as platinum, are required to speed up these chemical reactions. Moreover, SOFCs have feverish temperatures, implying that even if they don’t need pricy catalysts, they can be built from expensive metal alloys that withstand scorching operating temperatures.
In recent years, fuel cell researchers have implemented Goldilocks strategy . With this strategy, fuel cells can be operated at about 500 °C, which is a midrange temperature. Chemical reactions driving fuel cells can occur quickly at this temperature; moreover, fuel cells can be built from cheaper metals, such as stainless steel.
Scientists have tried to build cells with catalysts borrowed from SOFCs. Although the devices worked well, only 200 milliwatts of power per square centimeter (mW/cm2) was generated from the electrode surface area. This power was less than the performance of PEM fuel cells and SOFCs.
To develop fuel cells on a commercial scale, fuel cells must produce at least 500 mW/cm2; this requirement has been mandated by the U.S. Department of Energy (DOE). According to a paper presented last year in the journal Science, material scientists have produced a fuel cell with intermediate operating temperature.
This fuel cell can produce power of 455 mW/cm2. Another research group had also successfully produced a fuel cell that operated at a temperature of 500 °C, which was reported last year in Nature. Both PEM fuel cells and SOFCs are like batteries, and they have two electrodes that are separated with an ion-conducting electrolyte.
At one electrode, fuel molecules are stripped off negatively charged electrons. These electrons pass through an external circuit and move to a second electrode. Meanwhile, protons are ripped off from fuel molecules, which move to the second electrode through the electrolyte. Here, they recombine with traveling electrons.
There is a weak connection between anode and electrolyte, which blocks protons from zipping through cathode. A thin but dense layer of catalyst was atop the bulk of anode catalyst, and protons would easily undergo a transition and move into the electrolyte.
Researchers investigated the composition of ceramic electrodes, making them more stable in presence of steam and carbon dioxide. According to a report submitted in the journal Nature Energy, the devices produced nearly 550 mW/cm2 at 500 °C. These cells were stable for several hours of operation , and these cells showed hardly any signs of degradation.
Few issues still need to be solved before introducing these devices into commercial market. Presently, cells are small in size. They have diameter of few centimeters. Researchers need to make cells of much larger diameter. Pulsed laser deposition technique was used to form a dense coating on the anode, but it is difficult to perform this technique on a large commercial scale.
All ceramic electrodes and electrolytes are extremely brittle in nature, so they are less durable for use in real-world conditions. If these limitations are overcome, then intermediate range fuel cells would function as renewable sources of energy.
These fuel cells would not only generate electricity but the generated electricity would be converted into hydrogen and other fuels for the purpose of storage. This energy would be later converted into electricity. Thus, the biggest challenge associated with renewable energy would be solved. These innovative fuel cells would store energy when the sun is not shining and when the wind is still.