ASU researchers look to photosynthesis as blueprint for fuels
In a recent paper posted in Nature Chemistry, the researchers said they used the idea of photosynthesis to convert sunlight into fuel and store it.
Chemistry professor Vladimiro Mujica said the work behind this Nature Chemistry publication is an excellent example of how theory and experiment need to talk to each other to advance knowledge on complex problems whose solution can have a considerable societal impact.
Mujica’s research is centered on modeling the behavior of complex physical and chemical systems.
“In this particular case, advanced theoretical and computational modeling was needed to understand key electron paramagnetic resonance, or EPR, experiments that clarify the nature of the proton and electron transfer in the system,” he said.
Chemistry professor Devens Gust said the idea behind this project is to learn how to use sunlight to split water and make hydrogen.
The work began when a group of researchers started collaborating in the early 1980s. In 2009, ASU faculty joined together to apply for a grant to the department of energy.
“We wanted to make a system which would take sunlight and make it fuel,” Gust said. "Since there isn’t any technologically useful system of that type in existence, we started to use for guidance natural technology which does the same thing.”
Gust said their idea was to try and learn the basic science of how photosynthesis works and use that information to make artificial systems and design fuels for humans rather than plants.
“Photosynthesis uses sunlight," he said. "It oxidizes water and makes fuels. Those are the fuels that humans use today like coal, oil and natural gas. About 85 percent of our energy comes from those sources.”
Photosynthesis is a system that makes fuel and does so with various components. There are components that absorb light and there are components that use the light energy to make electric chemical energy.
There are also components called catalysts that use the chemical energy to oxidize water and make hydrogen fuel.
Gust and his research team created a center called BISFuels that involves only ASU faculty. They sometimes collaborate with other research centers to bring in resources they don’t normally have to solve the problem.
Gust said they collaborated with some researchers from Argonne on their research paper because they were familiar with some areas that his team was not.
“That’s pretty common in science these days,” he said. “Solving really hard problems and have people working together who are familiar with other disciplines and can get the job done.”
Gust’s team has been trying to develop a system that utilizes all those components.
“We developed a system like that very recently and we’re currently trying to make it better and more efficient,” he said.
To make it more efficient they looked at how photosynthesis works.
“We made an artificial version of that and used those ideas in the simpler system that does the same thing,” Gust said. “It proves the efficiency of getting electrons out of water.”
Gust said they could do the basic process, but the key to making a useful system is making an efficient system so that as much energy as possible goes into the final fuel.
“We also have to make the system inexpensive, because we need to compete with fossil fuels,” he said. “Right now, the system we have that works best uses a couple of rare metals such iridium, which is extremely rare. The system also uses platinum, which is expensive."
The team’s goal is to ultimately make a system that produces enough energy to have an impact on the world while simultaneously making it inexpensive. Gust said there are a number of different research groups using ideas from natural systems to make artificial ones.
“We look back at photosynthesis, and we see what that process uses, and it uses cheaper metals like manganese, iron and nickel,” he said. “We need to find a system that uses those metals.”
Gust said it is important to find alternative fuel sources, because not only will fossil fuels eventually run out, they are also bad for the environment.
“When we burn fossil fuels, they release carbon dioxide, a gas that contributes to global warming, and it leads to pollution and possible problems with fracking for natural gas,” he said. “Those are the prices we pay for using fossil fuels, and we’d like to avoid those prices.”
Sometimes the resources aren’t located in the same areas, which causes geopolitical problems.
Alternative fuel sources like wind and solar also have their shortcomings.
“The problem with solar is that you can only make solar electricity when the sun is out, so at night, you don’t have any solar electricity,” said Gust. “Though there is plenty of it, there is more striking the earth than humans could possibly use. The trouble is you can’t use it to power anything directly and reasonably."
Gust said it will take a long time to develop alternative fuel sources because the energy enterprise of humans is one of the biggest and most complicated systems.
“We have to change all of that,” he said. "Changing all of that is a very long-term operation. It takes replacing all of the refineries and gas stations. That’s been a major hurdle we’ve been working on.”
Chemistry professor Ana Moore also worked on the project. She said one approach the team had taken to artificial photosynthesis is mimicry of the steps used by photosynthetic organisms to convert solar energy into chemical energy.
“We have a good structure now,” she said. “We know where the molecules are.”
She said the fuel they are focused on right now is hydrogen.
“Hydrogen is a good fuel," she said. "It produces a lot of water and fuel and heat that’s good, that is what is issued with fuel. It doesn’t produce anything but water. It doesn’t pollute.”
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