Issue 22, 2018

The chemical identity, state and structure of catalytically active centers during the electrochemical CO2 reduction on porous Fe–nitrogen–carbon (Fe–N–C) materials

Abstract

We report novel structure–activity relationships and explore the chemical state and structure of catalytically active sites under operando conditions during the electrochemical CO2 reduction reaction (CO2RR) catalyzed by a series of porous iron–nitrogen–carbon (FeNC) catalysts. The FeNC catalysts were synthesized from different nitrogen precursors and, as a result of this, exhibited quite distinct physical properties, such as BET surface areas and distinct chemical N-functionalities in varying ratios. The chemical diversity of the FeNC catalysts was harnessed to set up correlations between the catalytic CO2RR activity and their chemical nitrogen-functionalities, which provided a deeper understanding between catalyst chemistry and function. XPS measurements revealed a dominant role of porphyrin-like Fe–Nx motifs and pyridinic nitrogen species in catalyzing the overall reaction process. Operando EXAFS measurements revealed an unexpected change in the Fe oxidation state and associated coordination from Fe2+ to Fe1+. This redox change coincides with the onset of catalytic CH4 production around −0.9 VRHE. The ability of the solid state coordinative Fe1+–Nx moiety to form hydrocarbons from CO2 is remarkable, as it represents the solid-state analogue to molecular Fe1+ coordination compounds with the same catalytic capability under homogeneous catalytic environments. This finding highlights a conceptual bridge between heterogeneous and homogenous catalysis and contributes significantly to our fundamental understanding of the FeNC catalyst function in the CO2RR.

Graphical abstract: The chemical identity, state and structure of catalytically active centers during the electrochemical CO2 reduction on porous Fe–nitrogen–carbon (Fe–N–C) materials

Supplementary files

Article information

Article type
Edge Article
Submitted
30 Jan 2018
Accepted
02 Mey 2018
First published
03 Mey 2018
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2018,9, 5064-5073

The chemical identity, state and structure of catalytically active centers during the electrochemical CO2 reduction on porous Fe–nitrogen–carbon (Fe–N–C) materials

N. Leonard, W. Ju, I. Sinev, J. Steinberg, F. Luo, A. S. Varela, B. Roldan Cuenya and P. Strasser, Chem. Sci., 2018, 9, 5064 DOI: 10.1039/C8SC00491A

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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