Electrochemical behaviour of naked sub-nanometre sized copper clusters and effect of CO2

The study of the electrochemical behavior (in the presence of N-2 or CO2) of size-controlled naked Cu-5 and Cu-20 nanoclusters, prepared using a combination of gas-phase cluster ion sources, mass spectrometry, and soft-landing techniques, evidences some relevant results regarding the redox behavior of these sub-nanometre sized copper particles and the effect of CO2 on them. Cu-20 nanoclusters show anodic redox processes occurring at much lower potential with respect to Cu-5 nanoclusters, which behave relatively similar to much larger Cu particles. However, Cu-5 nanoclusters coordinate effectively CO2 (hydrogen carbonate) in solution, different from Cu-20 nanoclusters and larger Cu particles. This effect, rather than the redox behavior, is apparently connected to the ability of Cu-5 nanoclusters to reduce CO2 under cathodic conditions at low overpotential. Although preliminary, these results provide rather exciting indications on the possibility of realizing low overpotential electrocatalytic conversion of CO2.