"If we can generate syngas from carbon dioxide using only solar energy, we can use it as a precursor for methanol and other chemicals and fuels. This will greatly reduce the overall carbon dioxide emissions," said mizzetian, a professor of electronic and computer engineering at the University of Michigan, who led the study published in the proceedings of the National Academy of Sciences.

Syngas is mainly composed of hydrogen, carbon monoxide and a small amount of methane. It is usually extracted from fossil fuels with the help of electricity. In addition, toxic chemicals are often added to improve production efficiency.

Roksana Rashid, the first author of the study, said: "our new process is actually very simple, but it is exciting because it is non-toxic, sustainable and very cost-effective." Rashid conducted the experiment while studying for his doctorate in electronic and computer engineering at McGill University in Canada.

In order to create a process that uses only solar energy, Mi's team overcame the difficulty of decomposing carbon dioxide molecules, which are one of the most stable molecules in the universe. To this end, they added nanoparticles to semiconductor nanowires. These nanoparticles, made of gold coated with chromium oxide, attract carbon dioxide molecules and bend them, weakening the bond between carbon and oxygen.

Gallium nitride nanowires use light energy to release electrons and the positively charged space they leave behind, namely holes. These holes split water molecules, separating protons (hydrogen) from oxygen. Then, on metal catalysts, electrons decompose carbon dioxide to produce carbon monoxide, and sometimes absorb free hydrogen to produce methane. Methods of separating oxygen from other gases are being developed.

"Our technology reveals how to build distributed syngas production from air, water and sunlight," said Zhou Baowen, the corresponding author who co wrote the study with Xiaomi, a former postdoctoral researcher at Xiaomi's laboratories at McGill University and the University of Michigan.

By changing the ratio of gold to chromium oxide in nanoparticles, Mi's team was able to control the relative amount of hydrogen and carbon monoxide produced in the reaction. This is important because the ratio of hydrogen to carbon monoxide affects the ease of producing a fuel or chemical.

"Surprisingly, the synergy between gold and chromium oxide makes the carbon dioxide emission reduction efficiency of syngas higher and adjustable. This is impossible for single metal catalysts." "This brings many exciting opportunities that have not been considered before."

Xiaomi's adjustable syngas unit adopts a standard industrial manufacturing process and is scalable. Rashid used distilled water in the experiment, and electrolyte solutions such as seawater are also expected to play a role. MI has used it in related water separation research.

"The semiconductors we use for light absorption are based on silicon and gallium nitride, which are the most common semiconductor production. We use very few materials for gallium nitride. The thickness of each nanowire is about 1 micron."

Xiaomi's next goal is to improve the efficiency of the equipment, which is currently 0.89%. When 10% of light energy is converted into chemical energy, he hopes this technology can be used for renewable energy similar to solar cells.

The project is supported by the Alberta Energy Research Institute for emission reduction at McGill University in Canada (MI's former residence). The co authors are or were associated with McGill University. Rashid is currently a postdoctoral researcher in electronic and computer engineering at the University of Waterloo, Canada. He is currently an associate professor of Mechanical Engineering Department of Shanghai Jiaotong University.

Some intellectual property rights related to this work have been authorized to NS nanotechnology company and NX fuel company jointly founded by Xiaomi. The University of Michigan and Xiaomi have economic interests in these companies.