CO2 electroreduction on Cu operates via an alternative chain growth mechanism to form C–C bonds at elevated temperature and pressure

Future practical applications of the electrochemical CO₂ reduction reaction will probably involve the use of higher pressures and temperatures. However, most research on the copper-catalysed electrochemical CO₂ reduction reaction-the most widely studied system due to its C-C coupling ability-is typically performed under ambient conditions, and hence the mechanistic conclusions drawn also pertain to those conditions. Using a custom high-pressure, high-temperature electrochemical cell, we show here that on copper electrodes, the C-C coupling mechanism changes from the typical CO dimerization mechanism at low temperatures to a Fischer-Tropsch-like chain growth mechanism at temperatures above 125 °C (also requiring higher pressure). These results show that temperature and pressure are crucial parameters to consider in applied and mechanistic studies of the electrochemical reduction of CO₂ because they can open up alternative reaction pathways and alter known mechanisms.