Built-in Electric Field Promotes Interfacial Adsorption and Activation of CO 2 for C 1 Products over a Wide Potential Window.

The unsatisfactory adsorption and activation of CO 2 suppress electrochemical reduction over a wide potential window. Herein, the built-in electric field (BIEF) at the CeO 2 /In 2 O 3 n-n heterostructure realizes the C 1 (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 1 current density (-1.1 V) of the CeO 2 /In 2 O 3 heterostructure with a BIEF is about 2.0- and 3.2-fold that of In 2 O 3 and a physically mixed sample, respectively. The experimental and theoretical calculation results indicate that the introduction of CeO 2 triggered the charge redistribution and formed the BIEF at the interfaces, which enhanced the interfacial adsorption and activation of CO 2 at low overpotentials. Furthermore, the promoting effect was also extended to CeO 2 /In 2 S 3 . This work gives a deep understanding of BIEF engineering for highly efficient CO 2 electroreduction over a wide potential window.