Tuning the C 1 /C 2 Selectivity of Electrochemical CO 2 Reduction on Cu-CeO 2 Nanorods by Oxidation State Control.

Ceria (CeO 2 ) 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/CeO 2 interfaces and their impact on electrochemical processes remains unclear. Here, we present a Cu-CeO 2 nanorod (Cu-CeO 2 NR) selective electrochemical CO 2 reduction catalyst having a well-controlled Cu-CeO 2 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 Cu 2+ ions to (Cu 0 ,Cu 1+ ) nanoclusters. Unlike single atomic Cu, which produces C 1 products as the main product during electrochemical CO 2 reduction, the coexistence of (Cu 0 ,Cu 1+ ) clusters lowers the energy barrier for C-C coupling and enables the selective production of C 2+ hydrocarbons. As a result, the coexistence of (Cu 0 ,Cu 1+ ) in the clusters at the Cu-ceria interface results in a C 2+ 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.