2D Boron Imidazolate Framework Nanosheets with Electrocatalytic Applications for Oxygen Evolution and Carbon Dioxide Reduction Reaction.

Abstract

Ultrathin 2D materials possess unique properties that translate to enhanced efficiency as electrocatalysts, stimulating research toward methodologies that support their preparation. Herein, a two-step strategy is reported that involves the preparation of the new boron imidazolate framework (BIF-73) which is subsequently utilized as a precursor to yield the crystalline 2D nanosheet material (Fe@BIF-73-NS) via post-synthetic modification. This new electrocatalytic material stabilizes ultra-small (Fe2 O3 ) fragments resulting in an excellent electrocatalytic performance for the oxygen evolution reaction (OER: lower overpotential with 291 mV at the current density of 10 mA cm-2 ) and carbon dioxide reduction reaction (faradaic efficiency of CO reaching 88.6% at -1.8 V vs Ag/AgCl) without the need for noble metals. Additionally, theoretical calculations and microscopy reveal that the superior OER performance can be attributed to the increased exposure of binding sites within the material to which the catalytically active Fe3+ centers are bound through a post-synthetic modification procedure. A red-shift of the Fermi level around the valence band is observed and is proposed to be a result of the aforementioned interactions. This work opens an avenue toward the development of 2D functional metal organic framework nanosheets for energy conversion applications.