Constructing Synergistic Zn‐N₄ and Fe‐N₄O Dual‐Sites from the COF@MOF Derived Hollow Carbon for Oxygen Reduction Reaction

Abstract

Single-atom catalysts (SACs) are getting more attention in the field of electrochemical energy storage and conversation, including oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER), due to their welldefined active centers, tunable electron structure, maximum atom-utilization efficiency, and excellent durability. [1] Pyrolysis of metal-containing precursors is one of the most frequent approaches for SACs preparation. [2] With the atomic dispersion of catalysts, however, the increasing surface free energy results in atom aggregation to form metal clusters or nanoparticles in the thermal treatment. [3] Therefore, it is a challenge to obtain SACs with a high loading rate of metal via pyrolysis. Wei et al. synthesized atomic Zn (9.3 wt%) by adopting a low annealing rate method. [4a] Jiang et al. reported a high loading Zn atoms (11.3 wt%) supported on the N-doped hollow carbon derived from ZIF-8 covered polystyrene nanospheres. [4b] Additionally, Wan et al. developed a cascade anchoring strategy to obtain SACs with a 12.1 wt% metal loading rate [4c] and Huang et al. fabricated Co atoms (15.3 wt%) on graphenelike carbons by a salt-template method. [3c] However, developing a high atomic density is still under further exploration. Compared with the solo single-atom sites, dual-metal active sites have been demonstrated to have higher catalytic activity and selectivity for ORR. [5] Nevertheless, it is difficult to build the interaction between the dual-metal sites even on the same carbon support, because the low-density distribution of metal atoms resulted in the long distance between each other, and thus trended into isolated sites rather than synergistic sites. Therefore, developing carbon supports with highly dense atom distribution is the potential to provide a template to construct dual-metal active sites with synergistic roles.

Water pumping effect over the organic ions defined graphene oxide membrane impulses high flux desalination

“…1e). The spectra contain a G-band at 1615 cm −1 , arising from the first-order scattering of sp 2 carbon atoms in a 2D hexagonal lattice, and a D-band at 1360 cm −1 , ascribed to the vibrations of carbon atoms in plane terminations of disordered graphite [30][31][32][33][34] . Compared to the pristine GO, no visible changes in G-and D-band position were observed for the ion-intercalation GO samples.…”

Tuning the Site-to-Site Interaction in Ru–M (M = Co, Fe, Ni) Diatomic Electrocatalysts to Climb up the Volcano Plot of Oxygen Electroreduction

“…Single atomic catalysts (SACs) have emerged as potential alternatives to precious-metal-based catalysts in various heterogeneous catalytic reactions. − In particular, the metal–X–C (X = N, P, and S) moieties immobilized on a carbon substrate represent a typical atom-economic catalyst that delivers ultrahigh site utilization, remarkable activity, selectivity, and durability, thereby qualifying them as the new breed of cutting-edge systems in electrocatalytic oxygen reduction reactions (ORRs). , SACs have received widespread attention and shown great performances in metal–air batteries and proton-conducting membrane fuel cells, which are distinct from their bulk or nanosized counterparts, but challenges still remain. , Recent research activities on SACs have mainly focused on solving the practical problems of single atoms; either enhancing the activity by regulating the electronic structure and local coordination environments − or achieving the production of high single-atom concentration. , More recently, the rational manipulation of binuclear metallic sites has surged as a new effective way of designing a synergistic effect that can boost the reaction activity and selectivity of isolated atomic sites, and it has even reshaped the understanding of the reaction mechanism. − However, such an exploration heavily relies on the ideal atomic structure and therefore requires an accurate synthetic strategy to ensure precise site distribution.…”

Native Ligand Carbonization Renders Common Platinum Nanoparticles Highly Durable for Electrocatalytic Oxygen Reduction: Annealing Temperature Matters

“…[1][2][3] It is known that the sluggish cathodic kinetics of the oxygen reduction reaction (ORR) greatly limits the conversion efficiency of PEMFCs. [4,5] To date, Pt (or Pt-based alloys) nanoparticles (NPs) loaded on a carbon support are still the most promising ORR catalysts due to their intrinsically high activity. [6] However, Pt catalysts typically suffer from the poor durability during long-term operation, [7] which is one of the critical issues hampering the widespread applications of PEMFCs.…”