Cobalt and Nitrogen Codoped Graphene with Inserted Carbon Nanospheres as an Efficient Bifunctional Electrocatalyst for Oxygen Reduction and Evolution

Abstract

It is highly desirable but remains challenging to develop efficient bifunctional electrocatalysts for both the oxygen reduction and oxygen evolution reactions (ORR/OER) in rechargeable metal–air batteries and unitized regenerative fuel cells. Herein, we developed a facile and cost-effective strategy to prepare a cobalt and nitrogen codoped three-dimensional (3D) graphene catalyst through inserting carbon nanospheres into the interlayers of graphene sheets. The catalyst exhibited not only excellent ORR performance but also excellent OER performance, and both were greatly enhanced by the insertion of carbon nanospheres. Its activities for the ORR/OER ranked among the best for doped carbon catalysts thus far reported. Its overall oxygen electrode activity parameter (ΔE) was as low as 0.807 V, which was much lower than that of Pt/C, and made it comparable with the best nonprecious metal based catalysts to date. Furthermore, the catalyst exhibited excellent stability toward ORR and OER, making it a new noble-metal-free bifunctional catalyst for future applications in the fields of alternative energy conversion and storage systems.

Opening Two‐Dimensional Materials for Energy Conversion and Storage: A Concept

“…[117,[119][120][121] Other than the carbon-based nanomaterials, MoS 2 has also been reported that its edges are preferred sites for O 2 chemisorption. Generally, Co 3+/4+ and Ni 3+/4+ are known as active centers to incorporate with graphene for enhanced OER and ORR performance.…”

“…[128] Copyright 2014, American Chemical Society. [119] Copyright 2016, American Chemical Society. a,d) TEM image of Co-N-GCI.…”

Co Nanoparticles Confined in 3D Nitrogen‐Doped Porous Carbon Foams as Bifunctional Electrocatalysts for Long‐Life Rechargeable Zn–Air Batteries

“…have been widely reported due to their excellent bifunctional oxygen electrode activity. For instance, Co nanoparticles (NPs) and N‐codoped 3D graphene were synthesized via thrusting carbon nanospheres into the interlayers of graphene nanosheets and exhibited superior bifunctional oxygen electrode activity (Δ E = 0.81 V) . Very recently, Deng's group constructed an efficient and stable bifunctional oxygen electrode catalyst (Δ E = 0.80 V) by anchoring Fe NPs on N‐doped nanocarbon‐intercalated graphene .…”

“…Then, FeCo alloy NPs adhered on the inside wall of N‐doped carbon nanotubes were prepared by Ci and co‐workers and achieved a peak power density of 152 mW cm −2 in rechargeable Zn–air battery . This is because porous carbon materials typically possess excellent conductivity and rich porous structure, and thereby can facilitate the transfer of electrons and prevent the agglomeration of transition metal NPs . In addition, it was demonstrated that doping porous carbon materials with transition metal and nitrogen can form more effective active catalytic sites and further enhance the bifunctional catalytic activity .…”

A Novel Metal–Organic Framework Route to Embed Co Nanoparticles into Multi-Walled Carbon Nanotubes for Effective Oxygen Reduction in Alkaline Media

“…In recent years, as a result of the global energy crisis and environmental pollution, the search for cheap, efficient, and environmentally friendly alternative energy conversion and storage systems has aroused huge and sustained interest [1,2]. Hydrogen is a clean energy source, and fuel cells are the best way to utilize it.…”