The effect of carbon support on the oxygen reduction activity and durability of single-atom iron catalysts
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The effect of carbon support on the oxygen reduction activity and durability of single-atom iron catalysts Jin-Cheng Li, Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, PR China; Fok Ying Tung Research Institute, Hong Kong University of Science and Technology, Guangzhou 511458, PR China Dai-Ming Tang, Peng-Xiang Hou, Guo-Xian Li, Min Cheng, and Chang Liu, Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, PR China Hui-Ming Cheng, Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, PR China; Tsinghua-Berkeley Shenzhen Institute, Tsinghua University, Shenzhen 5108055, PR China Address all correspondence to Chang Liu and Peng-Xiang Hou at [email protected] and [email protected] (Received 24 June 2018; accepted 9 August 2018)
Abstract Owing to lack of a definitive correlation between carbon supports and catalytic activity of single-atom Fe-active sites, rational design and preparation of single-atom Fe catalysts have so far been elusive. Herein we designed and prepared one-dimensional core–shell nanostructured single-atom Fe catalysts, in which carbon nanofibers and carbon nanotubes with different crystallinities and electrical conductivities were used as supports to host single-atom Fe-active sites. It was found that the carbon supports with higher electrical conductivity accelerate charge transfer and enhance the oxygen reduction reaction (ORR) activity of single-atom Fe-active sites as well as the ORR durability of the final catalyst.
Introduction Proton exchange membrane fuel cells (PEMFCs) operated in acidic conditions are one of the most promising environmentfriendly electrochemical energy conversion devices for nextgeneration transportation applications due to their ultrahigh theoretical specific energy.[1] The oxygen reduction reaction (ORR) process at the cathode of PEMFCs involves O2 adsorption, O–O breaking and multi-step electron transfer with high-energy barriers, leading to sluggish kinetics and low efficiency.[2] In order to facilitate ORR toward a small overpotential, a high current density, and a long durability, highly efficient, and robust catalysts are needed. Noble-metal Pt-based materials are known as the best ORR catalysts in acidic conditions, but they suffer from conspicuous drawbacks of high cost, scarcity, and poor durability, which severely hinder their wide use in PEMFCs. Thus, extensive research work has been dedicated to exploring inexpensive catalysts with high activity and long-term durability to substitute Pt-based materials. Carbon-based catalysts, including metal-free heteroatoms (B, N, S, and P)-doped carbon materials[3–5] and noble-metalfree Fe–N–C materials,[6–8] are the most promising alternatives due to their desirable electrical conductivity, good chemical stability, and large surface area. Among them, Fe–N–C materials with N-coordinated single-at
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