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Tuning the Activity of Carbon for Electrocatalytic Hydrogen Evolution via an Iridium‐Cobalt Alloy Core Encapsulated in Nitrogen‐Doped Carbon Cages
Author(s) -
Jiang Peng,
Chen Jitang,
Wang Changlai,
Yang Kang,
Gong Shipeng,
Liu Shuai,
Lin Zhiyu,
Li Mengsi,
Xia Guoliang,
Yang Yang,
Su Jianwei,
Chen Qianwang
Publication year - 2018
Publication title -
advanced materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.707
H-Index - 527
eISSN - 1521-4095
pISSN - 0935-9648
DOI - 10.1002/adma.201705324
Subject(s) - electrocatalyst , materials science , graphene , overpotential , tafel equation , dopant , heteroatom , iridium , inorganic chemistry , chemical engineering , carbon fibers , catalysis , electrochemistry , nanotechnology , doping , chemistry , composite number , organic chemistry , electrode , composite material , ring (chemistry) , optoelectronics , engineering
Graphene, a 2D material consisting of a single layer of sp 2 ‐hybridized carbon, exhibits inert activity as an electrocatalyst, while the incorporation of heteroatoms (such as N) into the framework can tune its electronic properties. Because of the different electronegativity between N and C atoms, electrons will transfer from C to N in N‐doped graphene nanosheets, changing inert C atoms adjacent to the N‐dopants into active sites. Notwithstanding the achieved progress, its intrinsic activity in acidic media is still far from Pt/C. Here, a facile annealing strategy is adopted for Ir‐doped metal‐organic frameworks to synthesize IrCo nanoalloys encapsulated in N‐doped graphene layers. The highly active electrocatalyst, with remarkably reduced Ir loading (1.56 wt%), achieves an ultralow Tafel slope of 23 mV dec −1 and an overpotential of only 24 mV at a current density of 10 mA cm −2 in 0.5 m sulfuric acid solution. Such superior performance is even superior to the noble‐metal catalyst Pt. Surface structural and computational studies reveal that the superior behavior originates from the decreased Δ G H* for HER induced by the electrons transferred from the alloy core to the graphene layers, which is beneficial for enhancing CH binding.