Nanospheres help scale up fuel production from H2O and CO2.
McIntosh wants to do that by using the smallest of materials, nanoscale dots of cadmium sulfite, to help make fuel cheaply from water and carbon dioxide.
“The holy grail of energy is, ‘Can you take water and carbon dioxide and convert them to fuel?’” he says. A real-world solution, he adds, must be practical, renewable and inexpensive.
To find a scalable solution, McIntosh and Prof. Bryan Berger of chemical engineering try to coax bacteria to produce 2-nm spheres of cadmium sulfite that could help harness the energy in sunlight to produce fuel from water and carbon dioxide.
These small semiconductor particles, known as quantum dots, aren’t new. They are produced using toxic chemicals processed at high temperature, and can be bought for about $4,500 per gram – too expensive to be commercially useful, McIntosh says.
He and Berger work with common bacteria purified from soil on Lehigh’s campus that they evolved to convert toxic chemicals in their environment into quantum dots. The process happens in water, with salts, a small amount of sugar and a cadmium source, and without environmentally risky processing, McIntosh says.
With a seed grant from Lehigh, they have shown that the process can produce large quantities of cadmium sulfite quantum dots cheaply. “We can get a beaker full with a few hours of an undergraduate’s time and about $20,” he says.
When stimulated by light the quantum dots split off electrons with a lot of energy. “If you design quantum dots right, they have enough energy to split water into hydrogen atoms and to reduce CO2 to CO,” McIntosh says. “If you bind the components back together, you can potentially make methanol,” a liquid hydrocarbon fuel that could be used for transportation.
Various pieces of the puzzle – catalyzing the reactions with quantum dots and recombining the products into fuel – have been demonstrated in labs. The challenges that remain are to understand how the pieces can be made to work together and to ramp up production of the cadmium sulfite and enable affordable energy production.
McIntosh, Berger and Prof. Christopher Kiely of materials science and engineering are seeking a grant from the Advanced Research Projects Agency-Energy to produce quantum dots more efficiently and with the right properties for fuel cells.
“We think this is a potentially scalable way to make them,” McIntosh says. “If we can say [to the research community], ‘They’re basically free; what can you do with them?’ that would be huge.”
McIntosh also studies materials for solid oxide fuel cells, a technology that efficiently converts the energy in fuels to electricity. As a postdoc, he did neutron diffraction at Oak Ridge National Laboratory to understand the crystal structure of the materials he works with. Most neutron diffraction work is done at very low temperatures and under a vacuum, but the metal oxides McIntosh studies for fuel cell applications are active at high temperatures. The best he could do was to take room temperature readings and make calculations about higher temperature behavior.
“What does room temperature tell you about what happens at 700 degrees Celsius? Anything can happen in between.” So he worked with Oak Ridge scientists to develop a special component of their neutron beam apparatus that can take in-situ samples.
McIntosh enjoys the multifaceted challenge that being a Lehigh professor presents – the rhythm of research and teaching.
“I like to teach classes. Selfishly, it’s almost an instant reward.”
He tries to make undergraduate classes relaxed and interesting. “If I’m presenting material differently than I conceived it in advance, if I’m drawing things on the board I hadn’t planned, that to me is a good class,” he says. “Undergraduates aren’t expected to know the concepts already. They’re supposed to struggle. It’s my job to help them over the bar.”
With graduate students, McIntosh is more of a manager and authority figure. “They’re putting a large part of their future in your hands,” he says. “Their publication track – which I have guided – is what they live on.”
Combining these core roles “isn’t multitasking,” McIntosh says. “It’s more convergent skill sets. It’s how I keep myself challenged.”