NiCoFe‐Layered Double Hydroxides/N‐Doped Graphene Oxide Array Colloid Composite as an Efficient Bifunctional Catalyst for Oxygen Electrocatalytic Reactions

• Published in: Advanced energy materials 2018-03, Vol.8 (9), p.n/a
• Main Authors: Zhou, Daojin, Cai, Zhao, Lei, Xiaodong, Tian, Weiliang, Bi, Yongmin, Jia, Yin, Han, Nana, Gao, Tengfei, Zhang, Qian, Kuang, Yun, Pan, Junqing, Sun, Xiaoming, Duan, Xue
• Format: Article
• Language: English
• Subjects: array‐like structures; bifunctional catalysts; Catalysis; Catalysts; Chemical evolution; Chemical reduction; Colloids; Graphene; Hydroxides; in situ growth; layered double hydroxide; Nickel; Nitrogen; N‐doped graphene; Structural hierarchy
• ISSN: 1614-6832; 1614-6840
• DOI: 10.1002/aenm.201701905

Ternary NiCoFe‐layered double hydroxide (NiCoIIIFe‐LDH) with Co3+ is grafted on nitrogen‐doped graphene oxide (N‐GO) by an in situ growth route. The array‐like colloid composite of NiCoIIIFe‐LDH/N‐GO is used as a bifunctional catalyst for both oxygen evolution/reduction reactions (OER/ORR). The NiCoIIIFe‐LDH/N‐GO array has a 3D open structure with less stacking of LDHs and an enlarged specific surface area. The hierarchical structure design and novel material chemistry endow high activity propelling O2 redox. By exposing more amounts of Ni and Fe active sites, the NiCoIIIFe‐LDH/N‐GO illustrates a relatively low onset potential (1.41 V vs reversible hydrogen electrode) in 0.1 mol L−1 KOH solution under the OER process. Furthermore, by introducing high valence Co3+, the onset potential of this material in ORR is 0.88 V. The overvoltage difference is 0.769 V between OER and ORR. The key factors for the excellent bifunctional catalytic performance are believed to be the Co with a high valence, the N‐doping of graphene materials, and the highly exposed Ni and Fe active sites in the array‐like colloid composite. This work further demonstrates the possibility to exploit the application potential of LDHs as OER and ORR bifunctional electrochemical catalysts. NiCoFe‐layered double hydroxides with Co3+ are vertically grown on N doped graphene oxide by an in situ growth route. The changing of electronic structure induced by N atoms, Co3+, and highly exposed edge sites of NiCoFe‐LDH contribute together to the excellent OER and ORR performances of bifunctional catalyst.