Engineering Molecular Heterostructured Catalyst for Oxygen Reduction Reaction

Abstract

Introducing a second metal species into atomically dispersed metal–nitrogen–carbon (M–N–C) catalysts to construct diatomic sites (DASs) is an effective strategy to elevate their activities and stabilities. However, the common pyrolysis-based method usually leads to substantial uncertainty for the formation of DASs, and the precise identification of the resulting DASs is also rather difficult. In this regard, we developed a two-step specific-adsorption strategy (pyrolysis-free) and constructed a DAS catalyst featuring FeCo “molecular heterostructures” (FeCo-MHs). In order to rule out the possibility of the two apparently neighboring (in the electron microscopy image) Fe/Co atoms being dispersed respectively on the top/bottom surfaces of the carbon support and thus forming “false” MHs, we conducted in situ rotation (by 8°, far above the critical angle of 5.3°) and directly identified the individual FeCo-MHs. The formation of FeCo-MHs could modulate the magnetic moments of the metal centers and increase the ratio of low-spin Fe(II)–N4 moiety; thus the intrinsic activity could be optimized at the apex of the volcano-plot (a relationship as a function of magnetic moments of metal–phthalocyanine complexes and catalytic activities). The FeCo-MHs catalyst displays an exceptional ORR activity (E 1/2 = 0.95 V) and could be used to construct high-performance cathodes for hydroxide exchange membrane fuel cells and zinc–air batteries.

Spatial engineering of single-atom Fe adjacent to Cu-assisted nanozymes for biomimetic O2 activation

“…2 i, j , the magnified iDPC-STEM images provide a much enhanced signal-to-noise ratio for the spatial characteristics of FePc@2D-Cu–N–C compared with the HAADF-STEM images. Detailed features of Fe–Cu bimetallic pairs in the vertically stacked FePc@2D-Cu–N–C are highly dependent on their orientations 42 . Additionally, HAADF-STEM with atomic-resolution electron energy-loss spectroscopy (EELS) elemental mapping was employed at a relatively low beam current 43 .…”

Harnessing single-atom catalysts for CO2electroreduction: a review of recent advances

“…In this regard, one of our recent works attempts to identify “true/false” DACs by using in situ rotation operation in AC-HAADF-STEM characterization. 172 Therefore, more precise synthesis strategies and more advanced characterization methods need to be further explored, as the precise synthesis and characterization of SACs are prerequisites for understanding their structure–function relationship.…”

Zn, Fe Dual-Atom Sites Catalyst Constructed by Metal Vacancy Strategy for Oxygen Reduction Reaction and Zn-Air Battery

“…The experimental setup of ZAB was assembled based on our previous work . First, the catalyst ink was prepared as follows: 5 mg of catalyst was dispersed in the mixture composed of 500 μL of deionized water, 450 μL of anhydrous ethanol, and 50 μL of Nafion; then, the obtained mixture was ultrasonicated for 30 min.…”