Synergistic Coupling Derived Cobalt Oxide with Nitrogenated Holey Two-Dimensional Matrix as an Efficient Bifunctional Catalyst for Metal–Air Batteries

Abstract

Developing cost-effective, efficient bifunctional electrocatalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is the heart of metal−air batteries as a renewable-energy technology. Herein, welldistributed nanopolyhedron (NP) Co 3 O 4 grown on iron (Fe) encapsulated in graphitic layers on a nitrogenated, porous two-dimensional (2D) structure, namely, a C 2 N matrix, (NP Co 3 O 4 /Fe@C 2 N), presents an outstanding bifunctional catalytic activity with a comparable overpotential and Tafel slope to those of benchmark Pt/C and IrO 2 . The rationally designed atomic configuration of Co 3 O 4 on the C 2 N matrix has a well-controlled NP morphology with a (111) plane, leading to bifunctional activities for the ORR and OER. Interestingly, the specific interaction between the NP Co 3 O 4 nanoparticles and the C 2 N matrix introduces synergistic coupling and changes the electronic configuration of Co atoms and the C 2 N framework. Benefiting from the synergistic coupling of Co 3 O 4 with the C 2 N matrix, the NP Co 3 O 4 /Fe@C 2 N electrocatalyst exhibits exceptionally high stability and an even lower charge−discharge overpotential gap of 0.85 V at 15 mA cm −2 than that of the Pt/C+IrO 2 catalyst (1.01 V) in Zn−air batteries. This work provides insights into the rational design of a metal oxide on a C 2 N matrix for bifunctional, low-cost electrochemical catalysts.

Nanostructured Carbon Based Heterogeneous Electrocatalysts for Oxygen Evolution Reaction in Alkaline Media

“…The transition metal centers coordinated with N atoms are demonstrated as the primary active sites for the OER. Ideally, the transition metal would be achieved at the single‐atom level during the preparation . The transition metals include Ni, Co, and Fe, which can be integrated with nanocarbon materials via a variety of synthetic methods, such as pyrolysis, MOF‐derived treatment, and impregnation‐carbonization strategy, etc.…”

“…Among these transition metal compounds, transitional metal oxides (TMO x ) as one of the most common substitutes of noble metal based electrocatalysts for OER have been extensively explored because of their abundant raw material reserves and promising electrocatalytic properties in alkaline media . However, the electrocatalytic activities of traditional TMO x for OER are normally limited by the low conductivity, slow mass transport, and inadequate active sites . Combining highly conductive carbon materials with TMO x is a valid method to obtain efficient charge transport channels and the increased available active sites to enhance the electrocatalytic activity .…”

Bimetallic Iron–Cobalt Catalysts and Their Applications in Energy-Related Electrochemical Reactions

“…A similar trend due to the synergistic effect can also be observed in hybrids of metallic nanoparticles with metal oxides. Kim et al [81] rationally designed a cost-effective and efficient ORR catalyst. Well-distributed nanopolyhedron Co 3 O 4 grows on nitrogenated graphitic porous two-dimensional layers (C 2 N), which encapsulates Fe nanoparticles.…”

Molten‐Salt Media Synthesis of N‐Doped Carbon Tubes Containing Encapsulated Co Nanoparticles as a Bifunctional Air Cathode for Zinc‐Air Batteries

“…It was reported recently that the deposition of TM catalysts onto carbon‐based materials could effectively enhance their electrocatalytic performance due to both excellent electrical conductivity of the supports and synergistic effects between TM and carbon . For example, Co nanoparticles supported on nitrogen‐doped graphene were tested as bifunctional electrocatalysts for ORR and OER . Fe nanoparticles distributed within N‐doped mesoporous carbon fibre (CF) were prepared through electrospinning and a hydrogen‐activation method, and the obtained Fe/CF material exhibited excellent electrocatalytic activity towards ORR with long‐term durability comparable to that of a Pt/C catalyst .…”