Effect of carbon support on the catalytic activity of copper-based catalyst in CO2 electroreduction

Climate change caused by carbon dioxide anthropogenic emissions has turned into one of the most important environmental concerns of our society. Among the different actions proposed for mitigation of CO2 emissions, electrocatalytic reduction appears as a very promising technology for recycling CO2 to synthetic fuels and other valuable products. One of the most important challenges of this technology is the development of catalysts that allow obtaining high efficiencies in the reduction of the CO2 molecule. This work is focused in the development of Cu based nanostructured catalysts deposited on carbon supports. Supercritical fluid deposition (SFD) technique has been used for the copper deposition on three different carbon supports: carbon black (CB), carbon nanotubes (CNT) and reduced graphene oxide (rGO). SFD is an environmentally friendly technology that has demonstrated good results in the synthesis of nanomaterials. Results obtained in this work show that SFD technique allows a homogeneous deposition of copper nanoparticles on the different carbon supports used with deposition yields close to 90%. The average size of copper nanoparticles formed is between 13 and 19 nm. The activity of these catalysts (Cu/CB, Cu/CNT and Cu/rGO) in the electrocatalytic reduction of carbon dioxide has been carried out in gas phase in a PEM type electrochemical cell. Results show a higher CO2 conversion rate (around 40%) when using Cu/CNT catalyst. In every case, CO, formic acid and methane are the main reaction products obtained from the CO2 reduction. Nevertheless, Cu/CNT and Cu/CB catalysts promote the formation of CO, whereas formic acid is the main reaction product with Cu/rGO. This could be attributed to the presence of oxygenated groups observed in the rGO based catalyst. These results point out that the interaction between the copper nanoparticles and the carbon support plays an important role in the CO2 electrocatalytic reduction process.