Li Research Group Advances Green Technologies

Artist Rendition of Chemicals in Solution
Image credit: Scott Hilliard. Image shared under a Creative Commons license.

Members of Dr. Fanxing Li’s research group have significantly boosted the efficiency of two important chemical reaction techniques: splitting water to create hydrogen gas; and splitting carbon dioxide (CO2) to create carbon monoxide (CO). The products are valuable feedstocks for clean energy and chemical manufacturing applications.

The water-splitting process converts water into hydrogen gas with 90 percent efficiency, while the CO2-splitting process converts more than 98 percent of the CO2 into CO. In addition, the process uses the resulting oxygen to convert methane into syngas, which is a feedstock used to make fuels and other products.

“These advances are made possible by materials that we specifically designed to have the desired thermodynamic properties for each process,” says Dr. Li. “These properties had not been reported before unless you used rare earth materials.”

For the CO2-splitting process, the research team developed a nanocomposite of strontium ferrite dispersed in a chemically inert matrix of calcium oxide or manganese oxide. As CO2 flows over a packed bed of the nanocomposite, the nanocomposite splits the CO2 and captures one of the oxygen atoms. This reduces the CO2, leaving only CO behind.

“Previous CO2 conversion techniques have not been very efficient, converting well below 90 percent of the CO2 into CO,” Li says. “We reached conversion rates as high as 99 percent.” “And CO is valuable because it can be used to make a variety of chemical products, including everything from polymers to acetic acid.”

Meanwhile, the oxygen captured during the CO2-splitting process is combined with methane and converted into syngas using solar energy.

For the water-splitting process, the team created iron-doped barium manganese oxide particles. Other than the difference in materials, the process is remarkably similar. As water – in the form of steam – is run over a bed of the particles, the iron-doped barium manganese oxide splits the water molecules and captures oxygen atoms. This produces pure hydrogen gas.

“Our conversion here is 90 percent, which compares very favorably to other techniques – which are often in the 10-20 percent range,” says Vasudev Haribal, a CBE Ph.D. student in Dr. Li’s group and lead author of the paper on the water-splitting work.

The oxygen captured during the water-splitting process is used to make syngas, using the same technique used in the CO2-splitting process.

“We think both of these materials and processes represent significant steps forward,” Li says. “They use relatively inexpensive materials to efficiently extract valuable feedstock from resources that are either readily available (in the case of water) or are actually greenhouse gases (in the cases of CO2 and methane).

“We are now working on developing materials that are even more efficient.” “And we’re open to working with outside groups who are interested in scaling these processes up for manufacturing.”

The CO2-splitting paper, “Perovskite Nanocomposites as Effective CO2-Splitting Agents in a Cyclic Redox Scheme,” is published in the journal Science Advances. Lead author of the paper is Junshe Zhang, a former postdoctoral researcher in Dr. Li’s group who is now at Xi’an Jiaotong University in China. The paper was co-authored by Haribal. The work was done with support from the National Science Foundation, under grants CBET-1254351 and CBET-1510900, and the Kenan Institute at NC State.

The water-splitting paper, “Iron-Doped BaMnO3 for Hybrid Water Splitting and Syngas Generation,” is published in the journal ChemSusChem. The paper was co-first authored by Feng He, one of Dr. Li’s Ph.D. graduates, and Amit Mishra, a Ph.D. student in the group. The work was done with support from NSF, under grant CBET-1254351, and the Kenan Institute at NC State.

Dr. Li is corresponding author of both papers. He is an associate professor of chemical and biomolecular engineering and a University Faculty Scholar.

The original version of this article was written by Matt Shipman, Research Communications Lead with NC State News Services. The article appears as a front-page link on NSF Science360, the official STEM news feed of the National Science Foundation.