Enhancing NO3- reduction on BiFeO3/Cu cathode via ferroelectric polarization: A novel strategy for surface electronic structure regulation.

The electrostatic repulsion between nitrate (NO3-) and cathode electrons significantly hindered the efficiency of electrocatalytic NO3- reduction reaction. Herein, we innovatively propose to use ferroelectric polarization to regulate the surface electronic structure of the cathode (BiFeO3/Cu), thereby enhancing NO3- adsorption and improving NO3- reduction rate. Due to the varied electronic structure and the charged reactive sites induced by the ferroelectric polarization of BiFeO3, 91.67 % of NO3- was reduced within 5 h on the polarized BiFeO3/Cu (BFO/Cu∗) cathode, surpassing that of the unpolarized BFO/Cu (72.08 %) and pure Cu (42.96 %). Moreover, BFO/Cu∗ showed improved N2 selectivity than its unpolarized counterpart. The density functional theory (DFT) calculation results revealed lower adsorption energy of NO3- and lower NO-to-N2O2 coupling energy on BFO/Cu∗, demonstrating facilitated NO3- adsorption process and improved N2 selectivity by ferroelectric polarization. The charge density differences, and the projected density of state (PDOS) further proved the enhanced interactions of NO3- and N-species on the BFO/Cu∗ surface. In-situ differential electrochemical mass spectrometry (DEMS) tests indicated that NO3- was reduced via the deoxygenation and hydrogenation processes. This study opens up a new avenue to improve the reaction rate and selectivity of electrocatalytic reactions by regulating the surface electronic structure via the ferroelectric polarization.