A team of Czech researchers has developed a new device that converts carbon dioxide into ethanol using sunlight, achieving what they describe as a record conversion efficiency and solving a problem that has blocked similar technologies for years. The work comes from Charles University in Prague and was published in the journal Advanced Energy Materials.
At the center of the breakthrough is something the researchers call a nano-sandwich. The device is a photocathode, a material that absorbs light and drives a chemical reaction. For years, scientists have known that cuprous oxide was a promising candidate for this role. It is inexpensive, widely available, and absorbs sunlight well. The problem was that in water, under light, it degraded within minutes, making it impractical for any real application.
The Prague team, led by chemist Pavla Eliášová, solved that problem by combining cuprous oxide with a class of advanced two-dimensional materials called MXenes. Through carefully controlled heating, they created an ultrathin layer of titanium dioxide on the surface of the MXenes. That layer changes how the material behaves. The MXenes pull electric charge away from the cuprous oxide quickly, which slows the breakdown of the material while simultaneously using that charge to convert carbon dioxide into liquid fuel.
According to a report by Phys.org, Eliášová described the combination this way: "Surface-engineered MXene combined with cuprous oxide allowed us to unite the best of both materials. The copper base enables maximum utilization of light energy, while the conductive MXene framework ensures that the material remains active even after many hours of operation."
The efficiency number the team recorded, 2.74% solar-energy-to-ethanol conversion, represents a record for this type of device. But the researchers say the efficiency figure is not the only notable result. Many competing systems produce a mix of byproducts when converting CO2, which complicates any path toward industrial use. This photocathode produces only ethanol as its liquid output. That selectivity matters because it removes the need for expensive separation steps that would otherwise be required before the fuel could be used.
The work was a collaboration between Eliášová's group in the Chemistry Section of the Faculty of Science and Tomáš Hrbek from the Faculty of Mathematics and Physics, both at Charles University.
Laboratory testing showed the device remained functional over many hours of operation, a significant improvement over previous cuprous oxide systems that failed within tens of minutes. The researchers are now focused on two next steps: improving the overall stability of the photocathode further, and moving from laboratory conditions to larger-scale tests under real outdoor daylight.
Eliášová described where the research stands: "This is a major step forward for us. At the laboratory scale, the system works very well and produces ethanol over many hours. In the next step, we want to further reinforce the stability of the entire photocathode and begin testing on a larger scale and under real daylight conditions."
Converting carbon dioxide, a greenhouse gas, into a usable fuel using only sunlight has long been a target in green chemistry research. A working solar reactor that does this efficiently and without degrading quickly could eventually offer a way to produce fuel while pulling CO2 out of the atmosphere. The Charles University team's device does not yet operate at the scale needed for industrial production, but the results indicate the core material problem that blocked earlier versions of this technology may now have a workable solution.
