To understand how copper produces a broad range of products in electrochemical CO2 reduction, it is vital to grasp how a CO2 molecule coordinates with the surface's Cu atom. On treating such a problem, Sakaki et al. used molecular orbitals approaches to study CO2 transition metal complexes, showing the carbon atom of a CO2 molecule is favorable for coordination with the transition metal atom. This led to the common belief that a CO2 molecule coordinates with the copper metal surface through carbon atom. However, there seems to be a challenge of forming a copper-carbon bond, as binary carbides for copper are unknown in mineral or laboratory settings. A recent study revealed experimentally that supercritical CO2 can oxidize copper metal to CuxO species, suggesting that CO2 molecules coordinated to copper metal surface must be through the oxygen atom, not the carbon atom.