Achieving Near‐Unity CO Selectivity for CO₂ Electroreduction on an Iron‐Decorated Carbon Material

Abstract

A straightforward procedure has been developed to prepare a porous carbon material decorated with iron by direct pyrolysis of a mixture of a porous polymer and iron chloride. Characterization of the material with X-ray diffraction, X-ray absorption spectroscopy, and electron microscopy indicates the presence of iron carbide nanoparticles encapsulated inside the carbon matrix, and elemental mapping and cyanide poisoning experiments demonstrate the presence of atomic Fe centers, albeit in trace amounts, which are active sites for electrochemical CO 2 reduction. The encapsulated iron carbide nanoparticles are found to boost the catalytic activity of atomic Fe sites in the outer carbon layers, rendering the material highly active and selective for CO 2 reduction, although these atomic Fe sites are only present in trace amounts. The target material exhibits near-unity selectivity (98 %) for CO 2-to-CO conversion at a small overpotential (410 mV) in water. Furthermore, the material holds potential for practical application, as a current density over 30 mA cm À 2 and a selectivity of 93 % can be achieved in a flow cell.

Engineering Atomically Dispersed FeN4 Active Sites for CO2 Electroreduction

“…However, in this work, the Fe clusters would catalyze the formation of graphitic carbon shells surrounding them (Figure S20), rendering them inactive catalytically for both the hydrogen evolution reaction (HER), a parasitic side reaction, and the CO2RR. The role of such carbon‐encapsulated Fe species is still not very clear yet for the CO2RR, although it might boost the electron transfer to the primary FeN 4 sites and act as a catalytic promoter [45] …”

“…Ther ole of such carbon-encapsulated Fe species is still not very clear yet for the CO2RR, although it might boost the electron transfer to the primary FeN 4 sites and act as acatalytic promoter. [45]…”

Highly Scalable Conversion of Blood Protoporphyrin to Efficient Electrocatalyst for CO2‐to‐CO Conversion

“…[ 29 ] Core–shell fashion NPs are also observed in analogously synthesized carbon materials. [ 30,31 ]…”

“…Dispersed Fe atoms were proved to be active sites for CO 2 RR using poisoning with cyanide ions (CN − ) (Figure S8, Supporting Information). [ 31 ] At the same time, Fe and Fe 3 C NPs are known to be active for HER in aqueous electrolytes. Nevertheless, increased Fe‐based NP formation for H@C‐ T at T > 800 °C is not problematic in this respect because once these NPs become wrapped by carbon layers, HER is suppressed.…”

“…[ 29 ] In fact, FeC 3 NPs wrapped in carbon have recently been shown to promote CO 2 RR activity of atomic Fe sites decorated on the outer layer. [ 31 ]…”