MOF-Derived Isolated Fe Atoms Implanted in N-Doped 3D Hierarchical Carbon as an Efficient ORR Electrocatalyst in Both Alkaline and Acidic Media

Abstract

In order to improve the catalytic performance of oxygen reduction reaction (ORR), it is pivotal to increase the density and accessibility of the active sites. Herein, we have developed a template-free melamine-assisted cocalcined strategy to afford Fe-embedded and N-doped carbons (Fe–N–C) with not only high density of atomically dispersed Fe–N x active sites but also abundant three-dimensional interconnected mesopores by directly pyrolyzing Fe-ZIF-8 covered with a controllable melamine layer. It is demonstrated that the introduction of melamine in the precursor plays a key role in constructing various carbonized products with controllable morphology, porosity, and components. With an optimal mass ratio 1:1 of melamine to Fe-ZIF-8, the resultant Fe@MNC-1 exhibits excellent ORR activity and stability, which exceeds 20 wt % commercial Pt/C catalyst (with a half-wave potential of 0.88 V vs 0.85 V) in an alkaline electrolyte and is even comparable to the commercial Pt/C catalyst (with a half-wave potential of 0.78 V vs 0.80 V) in an acidic electrolyte. To the best of our knowledge, Fe@MNC-1 can be ranked among the best nonprecious metal electrocatalysts for ORR in both alkaline and acidic media. The present synthetic strategy may provide a new opportunity for the design and construction of metal–organic framework-derived nanomaterials with rational composition and a desired porous structure to boost their electrocatalytic performance.

A Wet Impregnation Strategy for Advanced FeNi‐Based Electrocatalysts towards Oxygen Evolution

“…[56] Generally, the catalytic activity of an electrocatalyst is mainly influenced by two factors, the intrinsic activity of catalytic sites and the exposed site number (that is related to the electrochemically active surface area). [57][58] In our case, it is proposed that the strong synergistic interaction between iron and nickel sites induce optimized electronic structures for active centers, thus causing improved catalytic activity. On the other hand, the relatively higher electrochemical active area would also contribute to the activity enhancement.…”

Single‐Atom and Dual‐Atom Electrocatalysts Derived from Metal Organic Frameworks: Current Progress and Perspectives

“…ZIF‐8 is a good precursor to prepare SACs owing to its N‐containing ligands, regular morphology and readily preparation at ambient temperatures [64–71] . Using Fe‐doped ZIF‐8 as precursors, Wu and co‐workers prepared atomically dispersed Fe in N‐doped carbons for ORR.…”

“…Coincidentally, Li et. al also used Fe(acac) 3 as Fe source in ZIF‐8 to prepare Fe−N x −C catalysts for ORR [68] . Moreover, they also used melamine to encapsulate ZIF‐8 to extend the porosity of the prepared catalysts.…”

“…ZIF-8 is a good precursor to prepare SACs owing to its Ncontaining ligands, regular morphology and readily preparation at ambient temperatures. [64][65][66][67][68][69][70][71] Using Fe-doped ZIF-8 as precursors, Wu and co-workers prepared atomically dispersed Fe in Ndoped carbons for ORR. In addition, the size of ZIF-8 was systematically adjusted from 20 to 1000 nm to investigate the size effect of carbon supports.…”

Soybean straw biomass-derived Fe–N co-doped porous carbon as an efficient electrocatalyst for oxygen reduction in both alkaline and acidic media

“…In this work, the RRDE measurements were carried out in a 0.1 M KOH and 0.1 M HCIO 4 solution under saturated oxygen conditions with a constant potential of 0.5 V (vs. SCE) on the ring electrode. The H 2 O 2 yield and the number of electrons transferred during the ORR reaction were calculated using the following equations: 18,19…”