Porous Carbon‐Hosted Atomically Dispersed Iron–Nitrogen Moiety as Enhanced Electrocatalysts for Oxygen Reduction Reaction in a Wide Range of pH

Abstract

As one of the alternatives to replace precious metal catalysts, transition-metal-nitrogen-carbon (M-N-C) electrocatalysts have attracted great research interest due to their low cost and good catalytic activities. Despite nanostructured M-N-C catalysts can achieve good electrochemical performances, they are vulnerable to aggregation and insufficient catalytic sites upon continuous catalytic reaction. In this work, metal-organic frameworks derived porous single-atom electrocatalysts (SAEs) were successfully prepared by simple pyrolysis procedure without any further posttreatment. Combining the X-ray absorption near-edge spectroscopy and electrochemical measurements, the SAEs have been identified with superior oxygen reduction reaction (ORR) activity and stability compared with Pt/C catalysts in alkaline condition. More impressively, the SAEs also show excellent ORR electrocatalytic performance in both acid and neutral media. This study of nonprecious catalysts provides new insights on nanoengineering catalytically active sites and porous structures for nonprecious metal ORR catalysis in a wide range of pH.

Carbon‐Supported Single Atom Catalysts for Electrochemical Energy Conversion and Storage

“…Consistent results have also been observed in other studies . However, it has been noted that in Fe‐NC materials, the presence of Fe and peroxide (an ORR intermediate) may cause degradation of organic ionomers and fuel cell membranes due to Fenton reaction .…”

“…In fact, this method has been adopted as a generic strategy for the synthesis of SACs in a carbon matrix. For instance, Ni and Fe SACs on NC have been prepared by confining Ni 2+ and Fe 3+ within the ZIF‐8 pores, respectively . Interestingly, when ZIF‐8 is replaced with Co‐containing BMOFs, FeCl 3 can still be encapsulated in the cavities, producing (Co,Fe)‐NC SACs .…”

“…In recent years, SACs have also found significant applications in electrochemical energy conversion and storage, in particular, ORR, OER, HER, and CO 2 RR, and the results suggest that the supporting substrates such as carbon‐based materials not only provide anchoring sites for the single metal atoms, offer good electrical conductance with the graphitic skeletons, but also manipulate the charge density and electronic structure of the metal atoms because of strong interfacial interactions between the metal atoms and adjacent carbon atoms. Such attributes may be exploited for the enhancement of the electrocatalytic performance due to generation of an increasing number of active sites.…”

When Nanozymes Meet Single‐Atom Catalysis

“…[47,48] Thes patial confinement strategy accomplishes the atomic dispersion of metal precursors with the help of porous nanomaterials. [49,50] Furthermore,elements such as nitrogen, oxygen, and sulfur form strong interactions with metal atoms,which can be used to rationally design coordination sites that bind metal atoms. [51][52][53] Meanwhile,s ome innovative approaches,s uch as electrochemical corrosion, [54] sacrificial templates, [55] photocatalytic reduction, [37] and thermal transformation [56] have been utilized to prepare SACs.O ptimization of these synthetic strategies has taken the metal loading of SACs to ahigh level-from 12.1 up to 20 wt %which is very promising for practical applications.…”

When Nanozymes Meet Single‐Atom Catalysis

“…Where the defect engineering strategy is concerned, richly concentrated defects in the support serve as “traps” capture metal irons with vacancies and unsaturated coordination sites . The spatial confinement strategy accomplishes the atomic dispersion of metal precursors with the help of porous nanomaterials . Furthermore, elements such as nitrogen, oxygen, and sulfur form strong interactions with metal atoms, which can be used to rationally design coordination sites that bind metal atoms .…”