Interpenetrating Triphase Cobalt‐Based Nanocomposites as Efficient Bifunctional Oxygen Electrocatalysts for Long‐Lasting Rechargeable Zn–Air Batteries

Abstract

Rational construction of atomic‐scale interfaces in multiphase nanocomposites is an intriguing and challenging approach to developing advanced catalysts for both oxygen reduction (ORR) and evolution reactions (OER). Herein, a hybrid of interpenetrating metallic Co and spinel Co3O4 “Janus” nanoparticles stitched in porous graphitized shells (Co/Co3O4@PGS) is synthesized via ionic exchange and redox between Co2+ and 2D metal–organic‐framework nanosheets. This strategy is proven to effectively establish highways for the transfer of electrons and reactants within the hybrid through interfacial engineering. Specifically, the phase interpenetration of mixed Co species and encapsulating porous graphitized shells provides an optimal charge/mass transport environment. Furthermore, the defect‐rich interfaces act as atomic‐traps to achieve exceptional adsorption capability for oxygen reactants. Finally, robust coupling between Co and N through intimate covalent bonds prohibits the detachment of nanoparticles. As a result, Co/Co3O4@PGS outperforms state‐of‐the‐art noble‐metal catalysts with a positive half‐wave potential of 0.89 V for ORR and a low potential of 1.58 V at 10 mA cm−2 for OER. In a practical demonstration, ultrastable cyclability with a record lifetime of over 800 h at 10 mA cm−2 is achieved by Zn–air batteries with Co/Co3O4@PGS within the rechargeable air electrode.

Multidimensional Ordered Bifunctional Air Electrode Enables Flash Reactants Shuttling for High‐Energy Flexible Zn‐Air Batteries

“…As for the lat tice fringes in Figure 2h, they reveal the characteristic lattice spacing of 0.205 nm corresponding to Co (111) plane, which is also in accord with the XRD analysis ( Figure S9, Supporting Information). [18,19,37] These micropores and mesopores in MPZCC@CNT are expected to elongate oxygen molecules trapping periods and enhance its interactions with catalytically active sites. [35] The dif fusion of carbon atoms start around the Co nanoparticles embedded in nanoridges at high temperature, and then the supersaturation of the dissolved carbon atoms induces the for mation of CNTs.…”

Hollow Multivoid Nanocuboids Derived from Ternary Ni–Co–Fe Prussian Blue Analog for Dual‐Electrocatalysis of Oxygen and Hydrogen Evolution Reactions

“…The advantages of MOF‐derived active materials in advanced energy conversion and storage applications have been recently applied to efficient electrocatalysts for fuel cells, metal–air batteries, and electrolyzers . For example, Gadipelli et al recently reported a design route for the synthesis of MOF‐derived electrocatalysts, in which zeolitic imidazolate framework was used as the template .…”

Tuning Interfacial Structures for Better Catalysis of Water Electrolysis

“…As demonstrated by Chen and co-workers, Janus Co/Co 3 O 4 NPs stitched into porous graphitised shells( Co/Co 3 O 4 @PGS) can be produced through at hreestep process ( Figure 5A and B). [35] ZIF-8 NSs were firstly synthesised as the precursor,t hen the reaction between ZIF-8 and cobalt nitrate hexahydrate in ethanolr esulted in partial ion exchange between Co II and Zn II in the Zn metal-organic framework (MOF) matrix, andc oordination between Co II and unsaturated N-atom groupso nt he Zn MOF surface. During the final pyrolysis process, cobalt(II) nitrate adsorbed on the surfaceo f MOFs was oxidised to Co 3 O 4 with the assistance of nitrate anions, whereas Co II within the MOF matrix was reduced to metallicc obalt throughar edox reactionw ith the organic ligands.I nt his way, Janus-structured Co/Co 3 O 4 catalysts were constructed.…”