Czech researchers from Charles University, Prague, led by Pavla Eliášová, have developed an advanced photocathode that helps convert the greenhouse gas carbon dioxide into pure ethanol using sunlight. The new technology solves a long-standing problem of material degradation in water, achieves record conversion efficiency, and opens the way toward sustainable production of green fuels.
Converting carbon dioxide (CO2) into useful fuels using solar energy represents the holy grail of modern green chemistry. The device enabling this conversion is called a solar reactor. Its key element is a photocathode: a material that absorbs light and enables the chemical reaction. Cuprous oxide long appeared to be an ideal material because it is inexpensive, readily available, and excels at capturing solar rays. In practice, however, it faced a fundamental obstacle: in an aqueous environment under light, it transforms and degrades extremely rapidly—much like iron undergoing swift corrosion—and loses its functionality within just tens of minutes.
The team from the Chemistry Section of the Faculty of Science, CU, led by Pavla Eliášová, in collaboration with Tomáš Hrbek from the Faculty of Mathematics and Physics, CU, resolved this issue by creating a unique "nano-sandwich". The scientists combined cuprous oxide with advanced two-dimensional materials called MXenes and, through precisely controlled heating, created an ultrathin layer of titanium dioxide on their surface. MXene modified in this way can rapidly drain electric charge from the cuprous oxide, thereby slowing down its decomposition. At the same time, it uses the charge further to convert carbon dioxide into liquid fuel.
"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," explains research team leader Pavla Eliášová from the Chemistry Section of the Faculty of Science, Charles University.
In laboratory tests, the new photocathode achieved a record solar-energy-to-ethanol conversion efficiency of 2,74 %. A crucial improvement is the formation of only a single product. While other systems often produce a mixture of byproducts, the material designed by the research team produces pure ethanol as its sole liquid product, which significantly simplifies its potential industrial application.
"This is a major step forward for us. On our 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," adds physical chemist Pavla Eliášová.
The research was conducted within the international European project DESIRED (Horizon Europe), with support from the Charles University Research Centre (UNCE) and the L'Oréal-UNESCO For Women in Science program.
Bibliographic Citation: Carrascosa, L. A. M., Linková, M., Remzová, M., Hrbek, T., & Eliášová, P. (2026). Surface-Engineered MXene/Cu2O Photocathodes for Selective Ethanol Production. Advanced Energy Materials. https://doi.org/10.1002/aenm.71469
