Scientists turn CO2, water into fuel copying plants
WASHINGTON, May 25: Water and carbon dioxide. That's all that plants need to create fuel for themselves by converting them, with the aid of sunlight, into glucose, which they then use to sustain themselves. What if we used these chemicals through an artificial form of photosynthesis to create not glucose but propane and other natural fuels?
Two scientists at the University of Illinois in the United States have done that by developing a process that relies on the same green light portion of the visible light spectrum that plants use to convert CO2 and water into liquified fuels.
As a result, they say, we could have another method for sucking excess CO2 out of the atmosphere and putting it to good use. We could fall back on such fuel when solar power is limited for lack of adequate sunshine or else when power demands peak. Converting CO2 into liquid fuel could also be a boon to green energy technology.
"The goal here is to produce complex, liquefiable hydrocarbons from excess CO2 and other sustainable resources such as sunlight," says Prashant Jain, a professor of chemistry who was a co-author of a study the two researchers have published in the journal Nature Communications. "Liquid fuels are ideal because they are easier, safer and more economical to transport than gas and, because they are made from long-chain molecules, contain more bonds, meaning they pack energy more densely," Jain adds.
By help of catalysts covered in gold nanoparticles, which can absorb sunlight well and do not easily degrade, green light from the sun is absorbed in order for electrons and protons to aid in the chemical reactions between CO2 and water. Essentially, they function as the pigment chlorophyll during natural photosynthesis.
Energy stored in the bonds of hydrocarbon fuel thus gained can then be freed in several ways. Simply burning the liquid fuel to free up the energy in it, however, would end up producing more CO2. That would be "counterproductive to the notion of harvesting and storing solar energy in the first place," Jain says.
"There are other, more unconventional potential uses from the hydrocarbons created from this process," he explains. "They could be used to power fuel cells for producing electrical current and voltage. There are labs across the world trying to figure out how the hydrocarbon-to-electricity conversion can be conducted efficiently."
Their work is not done yet, however. "We need to learn how to tune the catalyst to increase the efficiency of the chemical reactions," Jain notes. "Then we can start the hard work of determining how to go about scaling up the process. And [as with] any unconventional energy technology, there will be many economic feasibility questions to be answered as well."
Liquid fuels are better than gas as they are easier to transport, safer and pack in more energy, said scientists. Natural photosynthesis is the process by which green plants uses energy from the sun as well as water in the soil and carbon dioxide in the air to make food in the form of energy-dense glucose - a form of sugar.
Chlorophyll is the catalyst behind the reaction, as well as being the pigment that makes plants green and also absorbs sunlight. Instead of chlorophyll, however, scientists are replicating the reaction in the lab using a metal to absorb light energy.
This energy drives the transfer of electrons and protons in the chemical reactions between CO2 and water. The researchers from Illinois at Urbana-Champaign, found that gold nanoparticles work particularly well as a catalyst in artificial photosynthesis.
Their surfaces interact well with carbon dioxide and are efficient at absorbing light. Furthermore, due to gold's lack of reactivity, it does not break down or degrade after multiple rounds of use like other metals.
Dr Prashant Jain, co-author of the study said: 'Liquid fuels are ideal because they are easier, safer and more economical to transport than gas and, because they are made from long-chain molecules, contain more bonds - meaning they pack energy more densely.'
There are several ways in which the energy stored in hydrocarbons can be captured and turned into fuel. However, the conventional method of combustion - burning carbon dioxide - ends up producing more carbon dioxide, Dr Jain said.
'They could be used to power fuel cells for producing electrical current and voltage. There are labs across the world trying to figure out how the hydrocarbon-to-electricity conversion can be conducted efficiently,' Jain said.
Currently, the artificial photosynthesis process is nowhere near as efficient as it is in plants and the scientists admit they still need to fine tune the catalyst to increase the efficiency of the chemical reactions.
After this, they will think about making the process commercially viable. Dr Jain added: 'Then we can start the hard work of determining how to go about scaling up the process. 'And, like any unconventional energy technology, there will be many economic feasibility questions to be answered, as well.'
Previously, researchers at the University of Illinois at Urbana-Champaign and the University of California, Berkeley collaborated to make plants soak up the sun more quickly, which could lead to better crop yields. The report is published in the journal Nature Communications.