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Perovskites Key to New Type of Hydrogen Fuel Cell

Quantum mechanics help perovskites perform well in fuel cells

2 min read
Photo: You Zhou
Photo: You Zhou

Crystals known as perovskites promise to revolutionize solar cells. Now researchers have found that they could improve fuel cells as well.

Fuel cells convert the chemical energy stored in fuels such as hydrogen into electricity. They do so by reacting the fuel with oxygen or another oxidizing agent that can strip electrons from the fuel. An electrolyte—commonly a polymer or ceramic—interposed between the fuel and oxidizer helps shuttle ions within the fuel cell.

Fuel cells are typically more efficient and environmentally friendly than heat engines, such as the internal combustion engines that usually power cars. However, fuel cells are often limited by how well their electrolytes can prevent electrons from leaking through them at the interface where the fuel and the oxidizing agent meet. Such electron conduction not only reduces fuel cell power output, but it can also lead to catastrophic fractures in the electrolyte.

Now researchers suggest that perovskites could make up a new kind of fuel cell electrolyte that can suppress electron conduction. These crystals are inexpensive and easily produced in labs, and perovskite solar cells have recently exploded in popularity in the photovoltaic world because of how quickly they have caught up to silicon-based devices in efficiency.

Fuel cell electrolytes are often chosen by how well they allow only ions to conduct through them. Instead, the researchers started with a perovskite that was very conductive to both ions and electrons.

Many perovskites are substances known as strongly correlated materials, in which each electron has a complex influence on its counterparts. By exposing a perovskite to hydrogen fuel, the scientists found that the electrons donated by the hydrogen interacted with the electrons in the perovskite. The resulting collective quantum mechanical effect suppressed electron conduction through the perovskite by nearly 100 million-fold compared to the perovskite in its pristine state.

"We have demonstrated an entirely new approach to design solid electrolytes for electrochemical energy devices," says study senior author Shriram Ramanathan, a materials scientist at Purdue University. "This opens up a new field of materials research for fuel cells and batteries."

In experiments with a perovskite samarium nickelate electrolyte, the researchers found their fuel cell reached a maximum power output of 225 milliwatts per square centimeter at 500 degrees C, which they say is comparable to the best-performing proton-conducting fuel cells in the same temperature range.

Future research will focus on developing inexpensive electrodes that can interact well with the new electrolyte, and on scaling up the system for practical power generation in applications such as vehicles and portable devices, Ramanathan says.

The scientists detailed their findings online 16 May in the journal Nature.

The Conversation (0)
This photograph shows a car with the words “We Drive Solar” on the door, connected to a charging station. A windmill can be seen in the background.

The Dutch city of Utrecht is embracing vehicle-to-grid technology, an example of which is shown here—an EV connected to a bidirectional charger. The historic Rijn en Zon windmill provides a fitting background for this scene.

We Drive Solar

Hundreds of charging stations for electric vehicles dot Utrecht’s urban landscape in the Netherlands like little electric mushrooms. Unlike those you may have grown accustomed to seeing, many of these stations don’t just charge electric cars—they can also send power from vehicle batteries to the local utility grid for use by homes and businesses.

Debates over the feasibility and value of such vehicle-to-grid technology go back decades. Those arguments are not yet settled. But big automakers like Volkswagen, Nissan, and Hyundai have moved to produce the kinds of cars that can use such bidirectional chargers—alongside similar vehicle-to-home technology, whereby your car can power your house, say, during a blackout, as promoted by Ford with its new F-150 Lightning. Given the rapid uptake of electric vehicles, many people are thinking hard about how to make the best use of all that rolling battery power.

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