Carbon dioxide (CO2) is considered the main greenhouse gas, as well as the main cause of global warning. Therefore, using it as a raw material C1 to efficiently synthesise valuable chemical and industrial products, such as carbon monoxide, methanol, ethanol, formic acid, ureas and polycarbonates, among other high-value chemicals, is both an academic challenge and a social demand.
The IMEM group and the company B Braun Surgical have developed a catalyst of hydroxyapatite, which has been electrically polarised by a process of thermal stimulation to produce ethanol ecologically and selectively on the basis of CO2 and CH4. The reaction, which produces ethanol as the main product, functions efficiently at 95°C under the action of UV radiation and at 140°C in the absence of light. Although ethanol forms at the surface of the catalyst, with selectivity above 90%, through electrocatalytic reduction of CO2, the study of the reaction mechanism has revealed that the presence of water is crucial to promote the formation and stabilisation of reactive radicals. The plasticity of the catalyst means that the selectivity can be modulated, and the formation of ethanol reduced in favour of other valuable chemical products, such as formaldehyde and acetone.
As a test of concept, the proposed reaction was carried out successfully using air contaminated by road traffic. In this case, obtaining ethanol and other chemical compounds from polluted air opens up a new path to transform greenhouse gas emissions into valuable chemical products using simple catalysts based on a mineral that is abundant on Earth.