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

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.