Scientists in the United States have developed tiny, low-temperature methane fuel cells that could soon power laptops.

Reliability, temperature, and cost have remained as the obstacles in using solid-oxide fuel cells (SOFCs) to charge laptops and phones or drive the next generation of cars and trucks. Fuel cells operate by converting chemical energy -- from hydrogen or a hydrocarbon fuel such as methane -- into an electric current.

Researchers led by Shriram Ramanathan at the Harvard School of Engineering and Applied Sciences (SEAS) are increasingly optimistic about the commercial viability of the new technology.

The researchers have demonstrated a methane-fueled micro-SOFC operating at less than 500 degree Celsius. Traditional SOFCs have been operating at about 800 degree Celsius and using them to power up a smartphone is not feasible. Currently, laptops and smartphones primarily use lithium-ion batteries.

When fuel cells operate at lower temperatures, material reliability is less critical -- allowing, for example, the use of less expensive ceramics and metallic interconnects -- and the start-up time can be shorter. Low temperature is a holy grail in this field. If you can realize high-performance solid-oxide fuel cells that operate in the 300 degree Celsius range, you can use them in transportation vehicles and portable electronics, and with different types of fuels, said Ramanathan.

Until recently, hydrogen has been the primary fuel for SOFCs. Pure hydrogen, however, requires a greater amount of processing and is expensive to make, which limits the range of applications.

As methane begins to take over as the fuel of choice, the advances in temperature, reliability, and affordability should continue to reinforce each other.

Methane is a chemical compound whose relative abundance makes it an attractive fuel. However, it is a relatively potent greenhouse gas and compared with carbon dioxide, with a high global warming potential.

Future research at SEAS will explore new types of catalysts for methane SOFCs, with the goal of identifying affordable, earth-abundant materials that can help lower the operating temperature even further, Ramanathan said.

The study appears in the Journal of Power Sources this month.