Unlocking direct CO2 electrolysis to C3 products via electrolyte supersaturation

The electroreduction of CO2 has recently achieved notable progress in the formation of C2 products such as ethylene and ethanol. However, the direct synthesis of C3 products is considerably limited by the C2–C1 coupling reaction and the faradaic efficiency has remained low. Here we present a supersaturation strategy for the electrosynthesis of 2-propanol from CO2 in highly carbonated electrolytes. By controlling the CO2 concentration above the saturation limit, we have developed a co-electrodeposition method with suppressed galvanic replacement to obtain a CuAg alloy catalyst. In supersaturated conditions, the alloy achieved high performance for the production of 2-propanol with a faradaic efficiency of 56.7% and at a specific current density of 59.3 mA cm−2. Our investigations revealed that the presence of dispersed Ag atoms in Cu weakens the surface binding of intermediates in the middle position of the alkyl chain and strengthens the C–O bonds, which favours the formation of 2-propanol over 1-propanol. Direct CO2 electroreduction on Cu-based catalysts has been used to produce C2 products but yields of C3 products have remained low. Here a CO2 supersaturation strategy is used to promote electrodeposition of a highly alloyed CuAg electrode and its subsequent selectivity towards 2-propanol.