Abstract
Single-atom catalysts, in particular the Fe–N–C family of materials, have emerged as a promising alternative to platinum group metals in fuel cells as catalysts for the oxygen reduction reaction. Numerous theoretical studies have suggested that dual atom catalysts can appreciably accelerate catalytic reactions; nevertheless, the synthesis of these materials is highly challenging owing to metal atom clustering and aggregation into nanoparticles during high temperature synthesis treatment. In this work, dual metal atom catalysts are prepared by controlled post synthetic metal-coordination in a C2N-like material. The configuration of the active sites was confirmed by means of X-ray adsorption spectroscopy and scanning transmission electron microscopy. During oxygen reduction, the catalyst exhibited an activity of 2.4 ± 0.3 A gcarbon−1 at 0.8 V versus a reversible hydrogen electrode in acidic media, comparable to the most active in the literature. This work provides a novel approach for the targeted synthesis of catalysts containing dual metal sites in electrocatalysis.
Highlights
Nitrogen doped coordinated single metal atom catalysts have attracted widespread attention in the eld of electrochemistry owing to their well-de ned active sites, high metal utilisation, and catalytic activity.[1,2,3,4,5] In particular, iron–nitrogen–carbon catalysts have emerged as a potentially more sustainable alternative to platinum group metals (PGMs) in the oxygen reduction reaction (ORR),[6,7] the largest cause of overpotential in fuel cells
Numerous theoretical studies have suggested that dual atom catalysts can appreciably accelerate catalytic reactions; the synthesis of these materials is highly challenging owing to metal atom clustering and aggregation into nanoparticles during high temperature synthesis treatment
C2N-Like materials were prepared by pyrolysis of a crosslinked complex comprising hexaketocyclohexane and urea in the presence of magnesium chloride at temperatures between 700 and 1000 C (Scheme 1)
Summary
At the active site, surrounded by more inert elements (Au, C, N, S, Hg, etc.) could yield more optimal scaling relations between *OOH and *OH.[14,15,16,17] As such, dual metal atom catalysts should in principle require negligible overpotential to achieve high current densities, or orders of magnitude higher activity at a given overpotential These materials are inspired by the structure of enzymes active sites, which display two earthabundant metals, such as Fe, in atomic proximity, such as the cytochrome c oxidase.[18,19,20] While our theoretical understanding of the class of this materials has advanced enormously,[21,22,23,24,25] experimental progress has been more limited. The performance of the catalysts for the ORR was evaluated in acidic media, using rotating disk electrode measurements
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