Built-in Electric Field Promotes Interfacial Adsorption and Activation of CO₂ for C₁ Products over a Wide Potential Window

The unsatisfactory adsorption and activation of CO2 suppress electrochemical reduction over a wide potential window. Herein, the built-in electric field (BIEF) at the CeO2/In2O3 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 CeO2/In2O3 heterostructure with a BIEF is about 2.0- and 3.2-fold that of In2O3 and a physically mixed sample, respectively. The experimental and theoretical calculation results indicate that the introduction of CeO2 triggered the charge redistribution and formed the BIEF at the interfaces, which enhanced the interfacial adsorption and activation of CO2 at low overpotentials. Furthermore, the promoting effect was also extended to CeO2/In2S3. This work gives a deep understanding of BIEF engineering for highly efficient CO2 electroreduction over a wide potential window.