Tuning the C1 /C2 Selectivity of Electrochemical CO2 Reduction on Cu-CeO2 Nanorods by Oxidation State Control.

Ceria (CeO2 ) is one of the most extensively used rare earth oxides. Recently, it has been used as a support material for metal catalsts for electrochemical energy conversion. However, to date, the nature of metal/CeO2 interfaces and their impact on electrochemical processes remains unclear. Here, we present a Cu-CeO2 nanorod (Cu-CeO2 NR) selective electrochemical CO2 reduction catalyst having a well-controlled Cu-CeO2 interface. Using in operando analysis and computational techniques, we found that, on the application of a reductive electrochemical potential, Cu undergoes an abrupt change in solubility in the ceria matrix. In this window, Cu undergoes a transition from the thermodynamically less stable randomly dissolved single atomic Cu2+ ions to (Cu0 ,Cu1+ ) nanoclusters. Unlike single atomic Cu, which produces C1 products as the main product during electrochemical CO2 reduction, the coexistence of (Cu0 ,Cu1+ ) clusters lowers the energy barrier for C-C coupling and enables the selective production of C2+ hydrocarbons. As a result, the coexistence of (Cu0 ,Cu1+ ) in the clusters at the Cu-ceria interface results in a C2+ partial current density/unit Cu weight 27-times that of a corresponding Cu-carbon catalyst under the same conditions. This article is protected by copyright. All rights reserved.