Built-in Electric Field Promotes Interfacial Adsorption and Activation of CO for C Products over a Wide Potential Window.

The unsatisfactory adsorption and activation of CO suppress electrochemical reduction over a wide potential window. Herein, the built-in electric field (BIEF) at the CeO/InO n-n heterostructure realizes the C (CO and HCOO) selectivity over 90.0% in a broad range of potentials from -0.7 to -1.1 V with a maximum value of 98.7 ± 0.3% at -0.8 V. In addition, the C current density (-1.1 V) of the CeO/InO heterostructure with a BIEF is about 2.0- and 3.2-fold that of InO and a physically mixed sample, respectively. The experimental and theoretical calculation results indicate that the introduction of CeO triggered the charge redistribution and formed the BIEF at the interfaces, which enhanced the interfacial adsorption and activation of CO at low overpotentials. Furthermore, the promoting effect was also extended to CeO/InS. This work gives a deep understanding of BIEF engineering for highly efficient CO electroreduction over a wide potential window.