A Gas-phase Electrochemical Reactor for Carbon Dioxide Reduction back to Liquid Fuels

We report on the development of a novel electrochemical reactor working in gas phase for recycling CO2 back to liquid fuels. Operating in gas phase (without any solvent) has many benefits with respect to the conventional aqueous slurry reactors: no problems of CO2 solubility, easy and less costly recovery of the products, etc. The reaction mechanism of CO2 reduction is also quite different in gas phase and longer chains of products (oxygenates and hydrocarbons) can be obtained in comparison with C1 products in liquid phase. Particularly, competition between CO2 reduction process and water electrolysis (with generation of hydrogen) at the cathode side was investigated and discussed in this contribution. The understanding of these competitive phenomena is very significant in order to minimize H2 formation and increase the process efficiency. The electrocatalysts prepared for the cathode are based on nanostructured carbons (multiwalled carbon nanotubes) doped with suitable metal nanoparticles (such as Pt, Fe, Co and Cu). The skill of developing advanced nanostructured electrodes by modulating their properties during the synthesis allowed to improve the process performance, enhancing the productivity and also tuning the selectivity towards higher chain hydrocarbons and other chemicals. The CO2 reduction to liquid fuels by solar energy represents an attractive solution which may contribute to the alternative use of clean and renewable sources to cope with the depletion of fossil fuels. The target is to develop a sort of “artificial leaf” which may collect the solar energy as the nature does, by capturing directly CO2 and converting it back to fuels.