The chemical identity, state and structure of catalytically active centers during the electrochemical CO2 reduction on porous Fe–nitrogen–carbon (Fe–N–C) materials. Issue 22 (18th May 2018)

• Record Type: Journal Article
• Authors: Leonard, Nathaniel; Ju, Wen; Sinev, Ilya; Steinberg, Julian; Luo, Fang; Varela, Ana Sofia; Roldan Cuenya, Beatriz; Strasser, Peter
• Is Part Of: Chemical science. Volume 9:Issue 22(2018)
• Page Start: 5064
• Page End: 5073
• Publication Date: 2018-05-18
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/c8sc00491a
• Languages: English
• ISSNs: 2041-6520

Abstract

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 (CO2 RR) catalyzed by a series of porous iron–nitrogen–carbon (FeNC) catalysts. 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 (CO2 RR) 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 CO2 RR 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–N x 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 Fe 2+ to Fe 1+ . This redox change coincides with the onset of catalytic CH4 production around −0.9 VRHE . The ability of the solid state coordinative Fe 1+ –N x moiety to form hydrocarbons from CO2 is remarkable, as it represents the solid-state analogue to molecular Fe 1+ 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 CO2 RR.