Metal organic framework-modified nitrogen-doped graphene oxygen reduction reaction catalyst synthesized by nanoscale hig
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Research Letter
Metal organic framework-modified nitrogen-doped graphene oxygen reduction reaction catalyst synthesized by nanoscale high-energy wet ball-milling structural and electrochemical characterization Shiqiang Zhuang, Bharath Babu Nunna, and Eon Soo Lee, Department of Mechanical and Industrial Engineering, New Jersey Institute of Technology, Newark, New Jersey 07102, USA Address all correspondence to Eon Soo Lee at [email protected] (Received 27 July 2017; accepted 4 December 2017)
Abstract Nitrogen-doped graphene (N-G) is a promising non-platinum group metal catalyst for oxygen reduction reaction. A new N-G/metal organic framework (MOF) catalyst is derived by the modification of MOF on N-G catalysts to enhance the electrochemical performance of N-G by increasing the surface area and porosity in this paper. The characterization confirmed that the Brunauer–Emmett–Teller surface areas of N-G/MOF catalysts are 13–66 times larger than the original N-G catalyst. The highest current density (5.02 mA/cm2) and electron transfer number (3.93) of N-G/MOFs are higher than the N-G catalyst. The current density of N-G/MOF catalyst is even higher than 10 wt% Pt/C catalyst.
Introduction Over the past decades, a multitude of researches was performed on the investigation of the synthesis methodology and the catalysis mechanism of electrochemical catalysts with high catalytic performance and low material cost for the oxygen reduction reaction (ORR).(1,2) To reduce the physical cost of the fuel cell stacks, the alternative catalytic materials have been extensively studied, and a significant recent advance in non-platinum group metal catalysts has emerged with the advent of new carbon structures including carbon nanowires, nanotubes, and graphenes doped with nitrogen.(3–5) The advantages of carbon-based catalysts, such as low cost, and good ORR activity, stability, and selectivity, make them become promising ORR catalysts for electrochemical systems like proton exchange membrane fuel cells.(6) Recently, it has been demonstrated that the ORR catalytic activity of nitrogen-doped graphene (N-G) catalysts can be comparable to Pt catalysts.(7) The published electrochemical characterization results of N-G catalysts generated by the nanoscale high-energy wet (NHEW) ball-milling method are shown in Fig. S4. It shows that the ORR electron transfer number of N-G catalyst has reached to 3.87, which is comparable to the 3.95 of the 10 wt% Pt/C catalyst.(7) The synthesis mechanism and processing control of N-G catalysts have been well understood in the recently published paper.(7,8) Based on the previous research, an approach for the improvement of the catalytic performance of N-G catalysts was newly investigated. The approach is using the metal–organic framework (MOF) material to modify N-G catalysts with NHEW ball-milling method.
The MOF, such as Zeolitic imidazolate framework-8 (ZIF-8), is a new composite material. It consists of metal ions or clusters coordinated to often rigid organic molecules to form one-dimensional (1D), 2D, or 3
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