Atomically dispersed Fe ³⁺ sites catalyze efficient CO ₂ electroreduction to CO

Abstract

Currently, the most active electrocatalysts for the conversion of CO2 to CO are gold-based nanomaterials, whereas non–precious metal catalysts have shown low to modest activity. Here, we report a catalyst of dispersed single-atom iron sites that produces CO at an overpotential as low as 80 millivolts. Partial current density reaches 94 milliamperes per square centimeter at an overpotential of 340 millivolts. Operando x-ray absorption spectroscopy revealed the active sites to be discrete Fe3+ ions, coordinated to pyrrolic nitrogen (N) atoms of the N-doped carbon support, that maintain their +3 oxidation state during electrocatalysis, probably through electronic coupling to the conductive carbon support. Electrochemical data suggest that the Fe3+ sites derive their superior activity from faster CO2 adsorption and weaker CO absorption than that of conventional Fe2+ sites.

Engineering Local Coordination Environments of Atomically Dispersed and Heteroatom‐Coordinated Single Metal Site Electrocatalysts for Clean Energy‐Conversion

“…The EXAFS is sensitive to the local structure without the need of long‐range order, thus it can provide information about the coordination number and bond distance of the SACs. The X‐ray photoelectron spectroscopy (XPS) can also reflect the oxidation states, chemical environments, and bonding information of the metal centers and its surrounding heteroatoms (e.g., N and S), which is usually used to supplement and support the results of XAS analysis . For Fe‐based SACs, the 57 Fe Mössbauer spectroscopy is a fingerprint technique that reflects the local electronic structure and coordination state of the Fe metal center .…”

“…The type of coordinated N atoms is another factor to determine the oxidation states of the Fe center. In principle, the Fe 3+ ions are more active than Fe 2+ ions due to the enhanced CO 2 adsorption and CO desorption . The operando XAS technology showed that pyrrole‐type N promotes the stability of Fe 3+ more than Fe 2+ , while the pyridine‐type N has an opposite effect.…”

Heterogeneous Single Atom Electrocatalysis, Where “Singles” Are “Married”

“…Copyright 2011, 2013 and 2018, Nature Publishing Group. Reproduced with permission . Copyright 2016, 2019 and 2012, American Association for the Advancement of Science (AAAS).…”

Highly Selective Electrochemical Reduction of CO2 to Alcohols on an FeP Nanoarray

“…Iron macrocyclic complexes are one of the most extensively researched categories of molecular catalysts for selective CO 2 reduction to CO . Because of the synthetic issues of such complexes, it is challenging to effectively immobilize them onto electrodes for practical application, which can be avoided by heterogeneous alternatives . A porous Fe 3 N single crystal was reported to yield CO with a selectivity of 90 % .…”

“…Singly dispersed FeN 5 active sites supported on N‐doped graphene enables CO 2 ‐to‐CO conversion with a FE of about 97.0 % . Recent study suggests that discrete Fe 3+ ions coordinated to pyrrolic nitrogen atoms of the N‐doped carbon support have ultrahigh activity for CO 2 electroreduction to CO . Compared with CO, alcohols possess advantages of higher energy density and easier storage at atmospheric pressure, and they are also widely used to feed the direct alcohols fuel cells .…”