Edwin L. Aguirre
A team of researchers from the Chemistry Department
has found a way to safely, cleanly and efficiently produce hydrogen gas that can be used to power the next generation of electric vehicles.
“Hydrogen burns completely clean – it produces no carbon dioxide, only water,” says Prof. David K. Ryan
, who chairs the department and is the project’s principal investigator. “And you don’t have to burn hydrogen to generate electricity. Hydrogen can be used in fuel cells
, which combine hydrogen with oxygen from the air to produce electricity at up to 85 percent efficiency.”
According to Ryan, their technique uses only water, carbon dioxide and cobalt metal particles with surface nanostructures measuring billionths of a meter in size to produce hydrogen on demand at relatively low temperature and pressure.
“This is original research. Nobody has done this kind of work before,” notes Ryan. “Other investigators have used all kinds of methods to produce hydrogen, such as electrolysis, natural gas reforming and even metals such as zinc, iron and nickel with acids, but not catalytically with cobalt.”
Aside from Ryan, other members of the team include chemistry Ph.D. students Ahmed Jawhari, Kehley Davies and Elizabeth Farrell and chemical engineering senior and Honors student Colleen Ahern.
The Massachusetts Clean Energy Center has awarded Ryan a $25,000 seed grant to get the team started on the path of commercializing the technology; he will also be applying for state and federal funding. The invention was recently awarded a provisional patent; a full patent is still pending.
According to BBC Research, the estimated market for hydrogen is currently about $5 billion. This is expected to grow to $180 billion by 2024, according to Global Market Insights, driven by increasing demand for clean energy. “The hydrogen market is poised for worldwide expansion,” says Ryan.
Power in a Canister
Despite its advantages, hydrogen fuel technology is still not used universally because of safety concerns about the highly flammable nature of the gas. (Many people still associate hydrogen with the Hindenburg disaster in 1937, when the hydrogen-filled passenger airship ignited and went down in flames.) Special storage requirements have to be considered when carrying hydrogen in cars, since a collision can accidentally release the gas and cause an explosion.
“Moreover, hydrogen is not mined or pumped out of the ground like fossil fuels; we have to produce hydrogen. Current hydrogen production methods are expensive and inefficient,” Ryan says. “This, coupled with the lack of existing infrastructure, has hampered the transition from a petroleum economy to a hydrogen economy. Our hope is that the catalytic hydrogen technology we have developed would help solve all of these challenges.”
The researchers’ experimental setup consists of a stainless steel canister filled with cobalt. They pump a carbonate solution made from carbon dioxide and water through the canister, and then warm it up to about 150 degrees. The solution is also compressed to about three atmospheres, or 45 pounds per square inch, which is about the same pressure as in a car tire.
“Under these relatively low temperature and modest pressure conditions, we were able to produce hydrogen efficiently, to nearly 70 percent. Subsequent work has allowed us to produce hydrogen at greater than 95 percent purity,” says Ryan.
He says that in this case, the cobalt carbonate is the catalyst, not the cobalt metal: “The carbonate is involved in the reaction but it doesn’t change or get consumed; it just helps facilitate the conversion of the cobalt metal to cobalt oxide, and this conversion produces the hydrogen and carbon dioxide.”
According to Ryan, in an electric car, the hydrogen from the canister can go directly to the fuel cell, where it is mixed with oxygen from the atmosphere to produce electricity and water. The water can then be looped back into the canister and mixed with the carbonate to form the catalytic solution. The electricity produced by the fuel cell can be used to power the canister’s pump, heater and compressor, as well as the car’s electric motors, rechargeable storage battery and headlights.
“This process doesn’t store any hydrogen gas, so it’s safe and poses no storage or transportation issues. Once you stop the flow of the carbonate solution or release pressure in the reaction chamber, the hydrogen production stops, so hydrogen is produced only as needed,” Ryan says.
Nanostructured cobalt metal, which comes in powder form, is stable and relatively safe to handle, says Ryan. Cobalt is not very expensive to mine or to produce synthetically. It is widely used in steel and other alloys as well as in magnets, batteries, electroplating and glass and ceramics.
Once the cobalt metal in the canister is used up – that is, converted to cobalt oxide – the car driver can swap out the canister with a new one every 300 to 400 miles. The cobalt in the old canister can then be regenerated, using a renewable energy source such as wind or solar.
“So instead of going to a gas station to get a fill-up, you can go to a ‘refueling’ station and get a new canister. You can also bring extras for long trips,” Ryan says.
A Serendipitous Discovery
The team’s catalytic hydrogen technology was actually discovered serendipitously while working on another research project: using cobalt as a catalyst to convert carbon dioxide from the atmosphere back to hydrocarbon fuels.
The researchers’ goal is to create a renewable cycle – you burn hydrocarbons as fuel and the carbon dioxide produced by the combustion is converted back to hydrocarbons. “This technology uses nanostructured cobalt and solar energy in a photo-catalytic process to produce hydrocarbons from carbon dioxide,” explains Ryan.
“In the process of doing this experiment, we found that we can produce hydrogen catalytically and with high efficiency,” he says.