title: Subnanometer Cobalt-Hydroxide-Anchored N-Doped Carbon Nanotube Forest for Bifunctional Oxygen Catalyst.
abstract: Electrochemical oxygen redox reactions are the crucial elements for energy conversion and storage including fuel cells and metal air batteries. Despite tremendous research efforts, developing high-efficient, low-cost, and durable bifunctional oxygen catalysts remains a major challenge. We report a new class of hybrid material consisting of subnanometer thick amorphous cobalt hydroxide anchored on NCNT as a durable ORR/OER bifunctional catalyst. Although amorphous cobalt species-based catalysts are known as good OER catalysts, hybridizing with NCNT successfully enhanced ORR activity by promoting a 4e reduction pathway. Abundant charge carriers in amorphous cobalt hydroxide are found to trigger the superior OER activity with high current density and low Tafel slope as low as 36 mV/decade. A remarkably high OER turnover frequency (TOF) of 2.3 s(-1) at an overpotential of 300 mV was obtained, one of the highest values reported so far. Moreover, the catalytic activity was maintained over 120 h of cycling. The unique subnanometer scale morphology of amorphous hydroxide cobalt species along with intimate cobalt species-NCNT interaction minimizes the deactivation of catalyst during prolonged repeated cycles.
authors.affiliation: National Creative Research Initiative (CRI) Center for Multi-Dimensional Directed Nanoscale Assembly, Department of Material Science and Engineering, KAIST , Daejeon 34141, Republic of Korea.
authors.forename: Ji Eun
authors.initials: JE
authors.lastname: Kim
authors.affiliation: National Creative Research Initiative (CRI) Center for Multi-Dimensional Directed Nanoscale Assembly, Department of Material Science and Engineering, KAIST , Daejeon 34141, Republic of Korea.
authors.forename: Joonwon
authors.initials: J
authors.lastname: Lim
authors.affiliation: National Creative Research Initiative (CRI) Center for Multi-Dimensional Directed Nanoscale Assembly, Department of Material Science and Engineering, KAIST , Daejeon 34141, Republic of Korea.
authors.forename: Gil Yong
authors.initials: GY
authors.lastname: Lee
authors.affiliation: Pohang Accelerator Laboratory (PAL), Pohang University of Science and Technology (POSTECH) , Pohang 37673, Republic of Korea.
authors.forename: Sun Hee
authors.initials: SH
authors.lastname: Choi
authors.affiliation: National Creative Research Initiative (CRI) Center for Multi-Dimensional Directed Nanoscale Assembly, Department of Material Science and Engineering, KAIST , Daejeon 34141, Republic of Korea.
authors.forename: Uday Narayan
authors.initials: UN
authors.lastname: Maiti
authors.affiliation: National Creative Research Initiative (CRI) Center for Multi-Dimensional Directed Nanoscale Assembly, Department of Material Science and Engineering, KAIST , Daejeon 34141, Republic of Korea.
authors.forename: Won Jun
authors.initials: WJ
authors.lastname: Lee
authors.affiliation: National Creative Research Initiative (CRI) Center for Multi-Dimensional Directed Nanoscale Assembly, Department of Material Science and Engineering, KAIST , Daejeon 34141, Republic of Korea.
authors.forename: Ho Jin
authors.initials: HJ
authors.lastname: Lee
authors.affiliation: National Creative Research Initiative (CRI) Center for Multi-Dimensional Directed Nanoscale Assembly, Department of Material Science and Engineering, KAIST , Daejeon 34141, Republic of Korea.
authors.forename: Sang Ouk
authors.initials: SO
authors.lastname: Kim
keywords: N-doping; amorphous metal oxide; bifunctional oxygen catalyst; carbon nanotubes; cobalt hydroxide