Crucial role of hydroxyl in CO selectivity for integrated CO2 capture and electrocatalytic reduction

Abstract As an integrated CO2 capture and utilization (ICCU) process, direct electrochemical reduction of amine captured-CO2 reduction reaction (cCO2RR) has enormous advantages in energy efficiency and operating cost. The low product selectivity is an urgent issue. Here, we found that the hydroxyl (-OH) on CeO2 can significantly enhance CO selectivity. After hydroxyl modification, the CO faraday efficiency (FECO) was surprisingly increased by 188% (relative increase rate). The correlation coefficient between -OH quantity and FECO is as high as 0.98. Further study indicated that the presence of -OH can lead to a more compact electrochemical double layer (EDL) and charge transfer resistance by proton transfer. The -OH can also enhance CO2 adsorption and stabilize the intermediate species (*COOH). DFT results further demonstrate that the rate-determining step was proton transfer from the surface -OH to MEACOO−, -OH modification can reduce the energy barrier to as low as 0.39 eV. This work provides additional insights into improving selectivity in amine-based cCO2RR, advancing the development of ICCU technology.