Edge-located Fe-N4 sites on porous Graphene-like nanosheets for boosting CO2 electroreduction

Abstract

• Various atomic Fe catalysts with adjustable porous architecture have been synthesized. • Electrochemical measurements indicate the CO 2 RR activity has positively relation to the number of e-ND-Fe(II). • The j CO of A-Fe@NG-Li 1 K 3 reaches an industrial-level value of 97 mA cm −2 at −0.45 V vs RHE in flow cell. • DFT calculations and in situ ATR-IR experiments reveal the intrinsic mechanism of CO 2 -to-CO conversion. The N-modified divacancies (NDs) configurations are critical to the intrinsic activity of Fe sites in Fe-N-C catalysts towards CO 2 reduction reaction (CO 2 RR), whereas the corresponding fundamental research is still challenging and insufficient. Herein, we report the synthesis of various atomic Fe catalysts A-Fe@NG-Li x K y with adjusted porous architecture. Electrochemical measurements indicate the CO 2 RR activity has positively relation to the ratio of edge-ND trapped Fe(II) sites [e-ND-Fe(II)] and center-ND trapped Fe(II) sites [c-ND-Fe(II)]. Theory calculations demonstrate e-ND-Fe(II) are energetically favorable for accelerating CO 2 RR, since the higher electron density around the Fe sites of e-ND-Fe(II) lowers the bonding of CO on the metal sites, which is confirmed by in situ attenuated total reflection-infrared spectroscopy experiments. The optimized sample A-Fe@NG-Li 1 K 3 exhibits ultrahigh activity for CO 2 RR with a small overpotential of 340 mV to achieve a CO partial current density at industrial application level (97 mA cm −2 ) with a CO Faradaic efficiency of 93%.