Chemical Kinetic Method for Active-Site Quantification in Fe-N-C Catalysts and Correlation with Molecular Probe and Spectroscopic Site-Counting Methods

Atomically Dispersed Metal–Nitrogen–Carbon Catalysts for Electrochemical Nitrogen Transformations to Ammonia and Beyond

“…The set of atomically dispersed mono- and bimetallic M–N–C catalysts experimentally utilized in this study are synthesized via the sacrificial support method (SSM), which is a hard templating method that mixes a metal-containing precursor with a sacrificial nanoporous silica that can be removed upon acid etching to yield a self-supporting catalyst. The SSM was first applied to M–N–C materials and reported by our group in 2008 and since then has undergone several optimizations. − A significant advantage of SSM-based catalysts is its tunable hierarchical pore structure, producing a significant portion of the active M–N x sites in its mesoporous volume, generating highly reactant accessible sites, in both the gas and liquid phase. , The general SSM synthesis procedure is shown in Figure a, where a metal salt precursor is mixed with a carbon–nitrogen-containing precursor (nicarbazin) and a variety of nanoporous silica. The nicarbazin carbon–nitrogen precursor is selected due to its low melting point, enabling it to melt into the porous structure of the silica prior to decomposition (observed by in situ scanning transmission electron microscopy, STEM) imparting the SSM’s characteristic hierarchical pore structure with a leading mesoporosity, as recently visualized via several in situ and operando technqiues. , After mechanical mixing, the catalyst is pyrolyzed under a reductive atmosphere.…”

The Effect of Sulfur and Nitrogen Doping on the Oxygen Reduction Performance of Graphene/Iron Oxide Electrocatalysts Prepared by Using Microwave-Assisted Synthesis

“…In the literature, many articles report how the introduction of heteroatoms (e.g., N, S, B, and P) into a carbon framework is able to effectively enhance the overall electrochemical activity for the ORR, as non-precious carbon-based catalysts [14][15][16][17][18]. Notably, co-doping has also been found to generally produce more active sites than single-atom doping, with a more efficient absorption capacity of oxygen molecules and, in the case of doping with S, leads to a better desorption of OH* [19].…”

A single-atom iron catalyst on hierarchical N-doped carbon for highly efficient oxygen reduction in Zn–air batteries

“…Among them, single-atom Fe–N–C catalysts with atomically dispersed Fe–N 4 active sites have garnered significant interest. 21–30 This attention can be attributed to their exceptional intrinsic activity, remarkable stability, abundant availability, 100% atom utilization, and cost-effectiveness, making them a potentially viable alternative to commercial Pt/C. 31–40 Nevertheless, it is worth highlighting that the pyrolysis process employed for synthesizing iron single-atom catalysts often leads to the formation of inactive Fe species and agglomerated components like nanoparticles.…”