Researchers from Charles University, Prague, Have Developed a New Photocathode for Efficient Conversion of CO2 into Ethanol

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.

Přf UK: Researchers from Charles University, Prague, Have Developed a New Photocathode for Efficient Conversion of CO2 into Ethanol

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.

Article

Surface-Engineered Ti3C2Tx MXene/Cu2O Photocathodes for Highly Selective Photoelectrocatalytic CO2 Reduction to Ethanol

Luis A. M. Carrascosa, Magdaléna Linková, Monika Remzová, Tomáš Hrbek, Pavla Eliášová

Adv. Energy Mater., 2026, 16, e71469

https://doi.org/10.1002/aenm.71469

licenced under CC-BY 4.0

Abstract

Cu₂O is an inexpensive p-type semiconductor that promotes the photoelectrocatalytic CO₂ reduction reaction (PEC CO₂RR). While its low bandgap enables photoexcitation by visible light, long-term stability remains limited due to quick charge recombination and photocorrosion. Here, we enhanced charge separation and extraction by combining Cu₂O with surface-engineered MXenes. In this novel architecture, TiO₂ grows in situ on the surface of Ti₃C₂T_x and serves as a charge-transport layer, forming a junction with Cu₂O. On the other side, the outer TiO₂ surface exposed to the CO₂-saturated electrolyte offers catalytically active sites for CO₂ reduction. Acting as a central layer, the MXene conductive backbone provides an electronically continuous pathway for electron transport. In PEC CO₂RR, the photocathode containing 50 wt.% of MXene and a balanced amount of TiO₂ on the Ti₃C₂ surface outperformed the best Cu/Cu_xO-based systems operating in non-organic electrolytes reported in the literature. The FTO/Cu₂O/ml-Ti₃C₂T_x-350-N₂ photocathode reached 8.4 µmol cm⁻² h⁻¹ ethanol production rate and 2.74% solar-to-ethanol efficiency after 2 h. Moreover, pairing TiO₂-MXene with Cu₂O significantly stabilized the photocathode, which maintained 76% of the ethanol production rate after 6 h. Overall, our results establish surface-engineered Cu₂O/TiO₂-MXene heterostructures as a solid platform for highly selective, visible-light-driven ethanol production with significantly improved operational stability.