Graphene-edge-supported iron dual-atom for oxygen reduction electrocatalysts

Pyrolyzed Fe-N-C-based catalysts, particularly FeN4, are reported to show enhanced catalytic activity for some chemical reactions, particularly for the oxygen reduction reaction (ORR). Here, we present a computational study to investigate another pyrolyzed Fe-N-C-based catalyst, i.e. Fe2N6, adsorbed on graphene with special emphasis on the edges of graphene nanoribbons (both zig-zag and armchair configurations) as a candidate for Fe dual-atom catalysts (Fe-DACs). Utilizing density functional theory calculations along with microkinetic simulations, we investigate the influence of graphitic edges on the stability and ORR activity of Fe-DAC active sites. Our findings indicate that the presence of graphitic edges, particularly the zig-zag configuration, significantly lowers the formation energy of Fe-DAC active sites, making them more likely to form at the edges. Furthermore, several Fe-DAC active sites at graphitic edges exhibit exceptional ORR performance, surpassing the commonly employed FeN4 active site in SAC systems and even exceeding the benchmark Pt(111) surface. Notably, the (Fe2N6)o@z1 active site demonstrates outstanding performance in both associative and dissociative mechanisms. These results highlight the role of graphitic nanopores in enhancing the catalytic behavior of Fe-DAC active sites, providing valuable insights for designing efficient non-precious metal catalysts for ORR applications.

Computational Screening of Single-Metal-Atom Embedded Graphene-Based Electrocatalysts Stabilized by Heteroatoms

Metal-N-doped carbon is a promising replacement for non-precious-metal catalysts such as Pt for the oxygen reduction reaction (ORR) in polymer electrolyte membrane fuel cells (PEMFCs). Although these materials have relatively good catalytic activity and are cost-effective, they still have lower ORR activity than Pt, and so improving their performances is greatly required. In this study, high-throughput screening was employed based on density functional theory (DFT) calculations to search for good candidate catalysts with a transition metal atom coordinated by heteroatoms (B, N, S, O, and P) embedded in a graphene structure. In addition, coordinating a transition metal with two types of heteroatom dopants in a graphene structure was also considered. We calculated the binding energies of ORR intermediates on metal-heteroatom-based graphene structures because they are known to play a key role in ORR. Based on our results, the new group of electrocatalysts imparts excellent ORR activity for PEMFCs, and we suggest that our approach provides useful insight into exploring other promising candidate catalysts.

Ionic liquid-derived Fe, N, S, F multiple heteroatom-doped carbon materials for enhanced oxygen reduction reaction

Heteroatoms doped carbon catalysts have been intensively studied to take the place of Platinum based catalysts for oxygen reduction reaction (ORR) because of their ideal catalytic activity. Herein, the microporous-mesoporous carbon material catalysts doped with Fe, N, S and F were synthesized through a plain one-pot pyrolysis method with ionic liquid 1-butyl-3-methyli-midazolium bis((trifluoromethyl)sulfonyl)imide ([Bmim][TF₂N]) and melamine as precursors. Electrochemical analysis shows that the ORR activity and stability of the obtained catalysts are obviously better than Pt/C under alkaline condition. Meanwhile, the catalysts show similar ORR activity and much better durability in 0.1 M HClO₄comparing to Pt/C. Moreover, the tolerance of methanol in both basic and acid solutions is greatly better than Pt/C. The high activity is ascribed to the large specific surface area, porous structure and the synergistic effect between S, F, pyridine N, graphite N and Fe-N_x. The high stability possibly comes from the appropriate graphitization and the carbon-coating effect. The strategy proposed here has the advantages of facile, low cost, high efficiency and easy large-scale production, which provides new ideas for the preparation of high-performance Fe-N-C electrocatalysts.

Effect of surface defects on the interaction of the oxygen molecule with the ZnO(101̄0) surface

Strong O₂–ZnO(101̄0) interactions can only occur when the ZnO(101̄0) surface has either an O vacancy or a Zn–O dimer vacancy.