From the source article:
Employing a catalyst made of copper nanoparticles embedded in spikes of carbon, the team found that electricity applied at just 1.2 volts was sufficient to convert CO2 suspended in water into ethanol.<p>From the abstract:
Herein we report a common element, nanostructured catalyst for the direct electrochemical conversion of CO2 to ethanol with high Faradaic efficiency (63 % at −1.2 V vs RHE) and high selectivity (84 %) that operates in water and at ambient temperature and pressure.