Effects of cobalt precursor on pyrolyzed carbon-supported cobalt-polypyrrole as electrocatalyst toward oxygen reduction reaction.

Xianxia Yuan,Hao-Dong Sha,Xin-Xin Hu,He Lin,Hai-Chuan Kong,Yong Yang,Xin-Long Ding,Zhi Guo,Guangxia Shen,Wen Wen,Zi-Feng Ma

doi:10.1186/1556-276x-8-478

Abstract

A series of non-precious metal electrocatalysts, namely pyrolyzed carbon-supported cobalt-polypyrrole, Co-PPy-TsOH/C, are synthesized with various cobalt precursors, including cobalt acetate, cobalt nitrate, cobalt oxalate, and cobalt chloride. The catalytic performance towards oxygen reduction reaction (ORR) is comparatively investigated with electrochemical techniques of cyclic voltammogram, rotating disk electrode and rotating ring-disk electrode. The results are analyzed and discussed employing physiochemical techniques of X-ray diffraction, transmission electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, inductively coupled plasma, elemental analysis, and extended X-ray absorption fine structure. It shows that the cobalt precursor plays an essential role on the synthesis process as well as microstructure and performance of the Co-PPy-TsOH/C catalysts towards ORR. Among the studied Co-PPy-TsOH/C catalysts, that prepared with cobalt acetate exhibits the best ORR performance. The crystallite/particle size of cobalt and its distribution as well as the graphitization degree of carbon in the catalyst greatly affects the catalytic performance of Co-PPy-TsOH/C towards ORR. Metallic cobalt is the main component in the active site in Co-PPy-TsOH/C for catalyzing ORR, but some other elements such as nitrogen are probably involved, too.

Highlights

With advantages of high power density, low-operating temperature, and low emissions, proton exchange membrane fuel cells (PEMFCs) have become new electrical sources for transportable and stationary applications in recent years
There is no doubt that oxygen reduction reaction (ORR) in the cathode of PEMFCs is a key factor determining the cell performance
PPy has been paid much more attention because of the porous structure, high surface area, high conductivity, easy synthesis and excellent environmental adaptability [18,19]. It can be used as a carrier of transition metal in the nitrogencontaining complex catalysts, where the metal particles can be fixed on its surface and physically dispersed, the interaction between PPy and metal particles can work as efficient active site for ORR [20,21]

Summary

Introduction

With advantages of high power density, low-operating temperature, and low emissions, proton exchange membrane fuel cells (PEMFCs) have become new electrical sources for transportable and stationary applications in recent years. The ORR generally proceeds by two pathways [1]: the direct four-electrontransfer reduction of oxygen that produces H2O and the two-electron-transfer reduction of oxygen yielding H2O2 which may be further reduced to H2O. PPy has been paid much more attention because of the porous structure, high surface area, high conductivity, easy synthesis and excellent environmental adaptability [18,19] It can be used as a carrier of transition metal in the nitrogencontaining complex catalysts, where the metal particles can be fixed on its surface and physically dispersed, the interaction between PPy and metal particles can work as efficient active site for ORR [20,21]. To identify the ORR mechanism, the actual ORR active site and the effects of preparation techniques/parameters on the catalytic performance of this kind of catalyst

Methods

Results

Conclusion