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ACS Nano. 2015 Feb 24;9(2):1977-84. doi: 10.1021/nn5069836. Epub 2015 Jan 27.

A superlattice of alternately stacked Ni-Fe hydroxide nanosheets and graphene for efficient splitting of water.

Author information

1
International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS) , Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan.

Abstract

Cost-effective electrocatalysts based on nonprecious metals for efficient water splitting are crucial for various technological applications represented by fuel cell. Here, 3d transition metal layered double hydroxides (LDHs) with varied contents of Ni and Fe were successfully synthesized through a homogeneous precipitation. The exfoliated Ni-Fe LDH nanosheets were heteroassembled with graphene oxide (GO) as well as reduced graphene oxide (rGO) into superlattice-like hybrids, in which two kinds of oppositely charged nanosheets are stacked face-to-face in alternating sequence. Heterostructured composites of Ni2/3Fe1/3 LDH nanosheets and GO (Ni2/3Fe1/3-GO) exhibited an excellent oxygen evolution reaction (OER) efficiency with a small overpotential of about 0.23 V and Tafel slope of 42 mV/decade. The activity was further improved via the combination of Ni2/3Fe1/3 LDH nanosheets with more conductive rGO (Ni2/3Fe1/3-rGO) to achieve an overpotential as low as 0.21 V and Tafel plot of 40 mV/decade. The catalytic activity was enhanced with an increased Fe content in the bimetallic Ni-Fe system. Moreover, the composite catalysts were found to be effective for hydrogen evolution reaction. An electrolyzer cell powered by a single AA battery of 1.5 V was demonstrated by using the bifunctional catalysts.

KEYWORDS:

graphene; heteroassembly; layered double hydroxide; nonprecious metal catalyst; water splitting

PMID:
25605063
DOI:
10.1021/nn5069836

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