Activity of N-coordinated multi-metal-atom active site structures for Pt-free oxygen reduction reaction catalysis: Role of *OH ligands

Abstract

We report calculated oxygen reduction reaction energy pathways on multi-metal-atom structures that have previously been shown to be thermodynamically favorable. We predict that such sites have the ability to spontaneously cleave the O2 bond and then will proceed to over-bind reaction intermediates. In particular, the *OH bound state has lower energy than the final 2 H2O state at positive potentials. Contrary to traditional surface catalysts, this *OH binding does not poison the multi-metal-atom site but acts as a modifying ligand that will spontaneously form in aqueous environments leading to new active sites that have higher catalytic activities. These *OH bound structures have the highest calculated activity to date.

Engineering Single‐Atom Cobalt Catalysts toward Improved Electrocatalysis

“…In this study, we show the direct evidences of the cobalt–adsorbate interactions and cobalt‐containing sites in SAC. Interestingly, our observations are further supported by the recent theoretical studies that the ORR adsorbates can serve as modifying ligands for metal sites, which could account for the highest calculated activity . Such strategies and insights may also be helpful in further performance enhancement and catalysts design of various SAC, which has shown promising prospects in many fields…”

“…It is generally believed that the favorable adsorption of adsorbates on catalytic sites is the crucial step toward effective ORR. Recently, the ORR‐related adsorbates have been demonstrated to be able to serve as a coordination ligand on surface metal sites . Therefore, such a downshift of unoccupied 3d orbitals toward lowered energy levels may favor the electronic interaction between the atomically dispersed cobalt sites and adsorbate ligands, leading to the facilitated charge transfer between the cobalt sites and adsorbates, and the consequent effective adsorption and reduction.…”

Computational and experimental evidence for a new TM–N3/C moiety family in non-PGM electrocatalysts

“…Configurations DV-Fe-N 2 (C1, C2) and DV-Fe-N 4 are shown in Fig. 42 Our results suggest that it should be easier to differentiate between V-Fe-N 3 /DV-Fe-N 4 , DV-Fe-N 3 , and DV-Fe-N 2 defects since their spectral features are predicted to be 0.4-0.6 eV apart. 4), rendering the correlation of spectral features and defect chemistry/geometry challenging.…”

Improving the Activity of M−N4 Catalysts for the Oxygen Reduction Reaction by Electrolyte Adsorption

“…The resulting increase in catalytic rate can then compensate for the reduced number of catalytic sites available, and can lead to an overall increase in activity. The presence of a ligand on one side of the active site has been indicated by experiments, and several theoretical reports have investigated the effect of spontaneously evolved ORR intermediates, as well as CN − , pyridine, Cl − , NH 2 , and NH 3 on the ORR activity . More recently, the effect of anions from the electrolyte was considered, and calculated adsorption energies were shown to correlate with the experimentally observed increase in ORR activity for an Fe−N/C catalyst in solutions of H 3 PO 4 and CH 3 COOH …”