Carbon-Coated Core–Shell Fe–Cu Nanoparticles as Highly Active and Durable Electrocatalysts for a Zn–Air Battery

Abstract

Understanding the interaction between a catalyst and oxygen has been a key step in designing better electrocatalysts for the oxygen reduction reaction (ORR) as well as applying them in metal-air batteries and fuel cells. Alloying has been studied to finely tune the catalysts' electronic structures to afford proper binding affinities for oxygen. Herein, we synthesized a noble-metal-free and nanosized transition metal CuFe alloy encapsulated with a graphitic carbon shell as a highly efficient and durable electrocatalyst for the ORR in alkaline solution. Theoretical models and experimental results demonstrated that the CuFe alloy has a more moderate binding strength for oxygen molecules as well as the final product, OH(-), thus facilitating the oxygen reduction process. Furthermore, the nitrogen-doped graphitic carbon-coated layer, formed catalytically under the influence of iron, affords enhanced charge transfer during the oxygen reduction process and superior durability. These benefits were successfully confirmed by realizing the catalyst application in a mechanically rechargeable Zn-air battery.

Pyrolytic Carbon‐coated Cu‐Fe Alloy Nanoparticles with High Catalytic Performance for Oxygen Electroreduction

“…The nanosizedm etal nanoparticles are uniformly dispersed on carbon matrixes ( Figure 1A). [8] The corresponding selected-areae lectron diffraction (SAED) image of FeCu@C-800s hows clear diffraction spots, indicating that the CuÀFe alloy nanoparticlesa re perfect single crystal.A s shown in Figure 1C and 1D,t he prepared CuÀFe alloy is completely encapsulatedi nacarbon shell.I no rder to further confirm the formationo ft he alloy nanoparticles, elemental mapping analysiso fF eCu@C-800i sp erformed by scanning transmissione lectron microscopy (STEM)t echnique (Figure 2A-D). [8] The corresponding selected-areae lectron diffraction (SAED) image of FeCu@C-800s hows clear diffraction spots, indicating that the CuÀFe alloy nanoparticlesa re perfect single crystal.A s shown in Figure 1C and 1D,t he prepared CuÀFe alloy is completely encapsulatedi nacarbon shell.I no rder to further confirm the formationo ft he alloy nanoparticles, elemental mapping analysiso fF eCu@C-800i sp erformed by scanning transmissione lectron microscopy (STEM)t echnique (Figure 2A-D).…”

“…The half-wavep otential for ORR over the Cu particles encapsulated in N-doped carbon shells reached0 .83 V RHE (relative to the reversible hydrogen electrode) and was 20 mV lower than that over the commercial Pt/ Cc atalyst. [8] These facts imply that the Cu-based materials may be the promising substitutes to commercialP t-based catalysts for ORR. [7] In addition, theoretical calculation hasp roved that Cu has the highest activity for oxygen reduction among the transition metals.…”

Towards a comprehensive understanding of FeCo coated with N-doped carbon as a stable bi-functional catalyst in acidic media

“…However, the formation of graphitic carbon layers on Cu surface is quite challenging. 23,38 For example, Nam et al 48 have noted that Fe catalyzes the crystallization of amorphous carbon into graphite, whereas Cu does not. Hence, we removed Cu@N-C from our list of candidates for good ORR catalysts.…”

First Principles Computational Study of Surface Reactions Toward Design Concepts of High Functional Electrocatalysts for Oxygen Reduction Reaction in a Fuel Cell System

“…It is interesting that encapsulating of the Pt-M or even non-precious catalyst with N-doped carbon shells was proposed as the promising solution [28][29][30]. The carbon shells not only tune the interaction strength between oxygen and the core metal but also close the path for surface segregation.…”