Photo-catalyst material converts CO2 into renewable hydrocarbon fuels

engineers work with lab equipment

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Researchers with the Department of Mechanical Engineering are making the best use of energy waste by turning carbon dioxide (CO2) into hydrocarbon fuels that can help the environment and solve growing energy needs.

“We’re essentially trying to convert CO2 and water, with the use of the sun, into solar fuels in a process called artificial photosynthesis,” Ying Li, an associate professor and Pioneer Natural Resources Faculty Fellow III, said. “In this process, the photo-catalyst material has some unique properties and acts as a semiconductor, absorbing the sunlight which excites the electrons in the semiconductor and gives them the electric potential to reduce water and CO2 into carbon monoxide and hydrogen, which together can be converted to liquid hydrocarbon fuels.”

The first step of the process involves capturing CO2 from emissions sources such as power plants that contribute to one-third of the global carbon emissions. As of yet, there is no technology capable of capturing the CO2, and at the same time re-converting it back into a fuel source that isn’t expensive. The material, which is a hybrid of titanium oxide and magnesium oxide, uses the magnesium oxide to absorb the CO2 and the titanium oxide to act as the photo-catalyst, generating electrons through sunlight that interact with the absorbed CO2 and water to generate the fuel.

The project is still in the fundamental research stage. One of the challenges with this technology is that the current conversion efficiency of converting CO2 and water into renewable solar fuels remains low, less than a few percent. According to Li, the conversion process also takes considerable time and the material can only absorb a fraction of the emitted sunlight. For Li and his team, solving these issues revolves around engineering more efficient materials with nano-scale structures and advancing the reactor design so that the materials placed within the reactor can absorb sunlight in the most efficient manner.

“There are also other considerations,” Huilei Zhao, a doctoral student contributing to the ongoing research in Li’s research group, said. “Concentrated sunlight exposure can lead to a higher conversion efficiency and we’ve found that if we operate at a higher temperature with this reaction, the conversion efficiency can be dramatically increased.”

The project is a part of a five-year research grant and CAREER Award for Li from the National Science Foundation, and is currently in its third year. By the end of the project, Li hopes to have developed a higher level of conversion efficiency and determine if the process can be commercially viable.

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