Site‐Specific Axial Oxygen Coordinated FeN₄ Active Sites for Highly Selective Electroreduction of Carbon Dioxide

Abstract

Regulating the coordination environment via heteroatoms to break the symmetrical electronic structure of M-N 4 active sites provides a promising route to engineer metal-nitrogen-carbon catalysts for electrochemical CO 2 reduction reaction. However, it remains challenging to realize a site-specific introduction of heteroatoms at atomic level due to their energetically unstable nature. Here, this paper reports a facile route via using an oxygen-and nitrogen-rich metal-organic framework (MOF) (IRMOF-3) as the precursor to construct the Fe-O and Fe-N chelation, simultaneously, resulting in an atomically dispersed axial O-coordinated FeN 4 active site. Compared to the FeN 4 active sites without O coordination, the formed FeN 4 -O sites exhibit much better catalytic performance toward CO, reaching a maximum FE CO of 95% at −0.50 V versus reversible hydrogen electrode. To the best of the authors' knowledge, such performance exceeds that of the existing Fe-N-C-based catalysts derived from sole N-rich MOFs. Density functional theory calculations indicate that the axial O-coordination regulates the binding energy of intermediates in the reaction pathways, resulting in a smoother desorption of CO and increased energy for the competitive hydrogen production.

Engineering the Interfacial Microenvironment via Surface Hydroxylation to Realize the Global Optimization of Electrochemical CO2 Reduction

“…All potentials were referred to the RHE with E RHE = E 0 Ag/AgCl + E Ag/AgCl + 0.059 × pH. 32,33 A BioLogic VMP3 electrochemical workstation was used to perform electrochemical experiments.…”

“…The electrocatalytic performance was characterized in a three-electrode H-type cell system with two-compartments separated by a Nafion N-117 membrane, including a reference electrode (Ag/AgCl electrode), a counter electrode (Pt plate), and a working electrode (catalyst-loaded carbon paper). All potentials were referred to the RHE with E RHE = E 0 Ag/AgCl + E Ag/AgCl + 0.059 × pH. , A BioLogic VMP3 electrochemical workstation was used to perform electrochemical experiments.…”

Controlled Modification of Axial Coordination for Transition‐Metal Single‐Atom Electrocatalyst

“…The carbon supported five‐coordinated Ni SACs (Ni−N 4 −O/C) exhibited a maximum FE about 100 % at −0.9 V. DFT calculations elucidated that the axial O ligands modulated the electronic structures of Ni sites and decreased the activation energy barriers of CO 2 RR, promoting the kinetics of CO 2 RR. In another work, an axial O was applied to modulate the electronic structure of Fe SACs with Fe−N 4 moieties, the newly formed FeN 4 O exhibited enhanced CO 2 RR activity and high selectivity towards CO compared with FeN 4 [39a] . Figure 4d showed the corresponding EXAFS fitting curves and configuration of the catalyst.…”

Regulating electron configuration of single Cu sites via unsaturated N,O-coordination for selective oxidation of benzene

“…The k 3 -weighted FT-EXAFS (Fig. 3b 2b, c), the Cu atom was presumed to be coordinated by a mixed structure of Cu-O and Cu-N [52][53][54] . The quantitative FT-EXAFS fitting analysis (Fig.…”