Temperature Effect of CO2Reduction Electrocatalysis on Copper: Potential Dependency of Activation Energy

The electrochemical CO(2)reduction reaction (CO2RR) has gathered widespread attention in the past decade as an enabling component to energy and fuel sustainability. Copper (Cu) is one of the few electrocatalysts that can convert CO(2)to higher-order hydrocarbons. We report the CO2RR on polycrystalline Cu from 5 degrees C to 45 degrees C as a function of electrochemical potential. Our result shows that selectivity shifts toward CH(4)at low temperature and H(2)at high temperature at the potential values between -0.95 V and -1.25 V versus reversible hydrogen electrode (RHE). We analyze the activation energy for each product and discuss the possible underlying mechanism based on their potential dependence. The activation barrier of CH(4)empirically obeys the Butler-Volmer equation, while C(2)H(4)and CO show a non-trivial trend. Our result suggests that the CH(4)production proceeds via a classical electrochemical pathway, likely the proton-coupled electron transfer of surface-saturated COad, while C(2)H(4)is limited by a more complex process, likely involving surface adsorbates. Our measurement is consistent with the view that the adsorbate-adsorbate interaction dictates the C(2+)selectivity.