Multifunctions of carbon dots in CeO2/Cu2O complex catalyst for the regulation of carbon dioxide reduction

Abstract

For electrocatalytic reactions, the charge transfer is a very complex process and also closely related to the chemical reaction process. Herein, taking the CO2 reduction reaction (CO2RR) as an example, we report the regulation of the CeO2/Cu2O-carbon dots (Ce-Cu-CDs) on CO2RR, and show the roles of the multifunctions of CDs in this complex catalyst system. The CeO2/Cu2O (Ce-Cu) catalyst exhibits the faraday efficiency (FE) for methane exceeding 50 % across a wide potential range (-1.2 V - -1.7 V vs. RHE) in the CO2RR. The acquired Ce-Cu-CDs catalyst reveals the transformation route of CDs with the ability to store electrons and regulate the CO2RR process. The electrocatalytic performance test with Ce-Cu-CDs shows that the FE of methane is potential dependent after the addition of CDs. The combination of transient photovoltage, transient potential scanning, density functional theory calculations and in-situ infrared spectroscopy has elucidated the multifunctions of CDs in the regulation of route in CO2RR, including the enhanced charge storage, the weakening of CO2 activation, the reduction of CO2 adsorption, the increase of the energy barrier of the rate-determining step of CO2 conversion to methane, the reduction of slow electron transfer and the reduction of slow electron transfer, thus altering the path of CO2RR process. This work unveils the ability of CDs to regulate the pathway of complex electrocatalytic process and provides a new example for the application of CDs in electrochemical reactions.