Czech scientists develop photocathode that converts CO2 into ethanol

Scientists from the Chemistry Section of the Faculty of Science at Charles University in Prague, led by Pavla Eliášová, working together with colleagues from the university's Faculty of Mathematics and Physics, have developed a new photocathode capable of converting carbon dioxide into ethanol using solar energy. The researcher shared the details herself, presenting the findings in a scientific paper.

The device is a key component of a so-called solar reactor — a system designed to turn carbon dioxide into usable fuel. The photocathode's job is to absorb light and trigger the necessary chemical reaction. According to Eliášová, using solar energy to convert CO2 in this way has long been considered the "holy grail" of modern green chemistry.

A side effect: producing alcohol

Interestingly, the technology could potentially find use not only in the chemical industry but also in food production — specifically for making distillates. Asked whether the process could be used to produce drinking alcohol, the scientist said it was indeed possible, depending on how an end producer chose to apply the process.

For a long time, copper(I) oxide was considered the ideal material for converting CO2 into alcohol: it's cheap, widely available, and absorbs sunlight extremely well. In practice, however, a major issue emerged — in water, under light exposure, it degraded very quickly, much like rusting iron, losing its properties within just a few dozen minutes.

The solution: a "nano-sandwich"

The Czech team found a way around this problem by creating a unique multilayer structure they themselves call a "nano-sandwich." They combined copper(I) oxide with cutting-edge two-dimensional materials known as MXenes, then used precisely controlled heating to form an ultrathin layer of titanium oxide on their surface.

This modified MXene is able to instantly draw electric charge away from the copper oxide, slowing down its degradation. At the same time, that charge is put to use converting carbon dioxide into liquid fuel. "The copper base ensures maximum use of light energy, while the conductive MXen structure keeps the material active even after many hours of operation," Eliášová explained.

Record efficiency and a pure end product

In laboratory tests, the new photocathode achieved a record-breaking solar-to-ethanol conversion efficiency of 2.74 percent. Crucially, the reaction yields only a single product: unlike many other systems that produce a mixture of by-products, the Czech team's device generates purely liquid ethanol, which significantly simplifies any potential industrial application of the technology.

"This is a major step forward for us. At the laboratory scale, the system performs very well and produces ethanol over many hours. The next step is to further strengthen the photocathode's stability and start testing it at a larger scale under real daylight conditions," added physical chemist Eliášová.

The research was carried out as part of the international European project DESIRED under the Horizon Europe programme, with support from Charles University's Research Centre (UNCE) and the L'Oréal-UNESCO "For Women in Science" programme.

Source: novinky.cz