5 years ago

Hierarchically Structured 3D Integrated Electrodes by Galvanic Replacement Reaction for Highly Efficient Water Splitting

Hierarchically Structured 3D Integrated Electrodes by Galvanic Replacement Reaction for Highly Efficient Water Splitting
Lvlv Ji, Zuofeng Chen, Shangshang Zuo, Jianying Wang
A NiFe-based integrated electrode is fabricated by the spontaneous galvanic replacement reaction on an iron foam. Driven by the different electrochemical potentials between Ni and Fe, the dissolution of surface Fe occurs with electroless plating of Ni on iron foam with no need to access instrumentation and input energy. A facile cyclic voltammetry treatment is subsequently applied to convert the metallic NiFe to NiFeOx. A series of analytical methods indicates formation of a NiFeOx film of nanosheets on the iron foam surface. This hierarchically structured three dimensional electrode displays high activity and durability against water oxidation. In 1 m KOH, a current density of 1000 mA cm−2 is achieved at an overpotential of only 300 mV. This method is readily extended to fabricate CoFe or NiCoFe-based integrated electrodes for water oxidation. Phosphorization of the bimetallic oxide (NiFeOx) generates the bimetallic phosphide (NiFe-P), which can act as an excellent electrocatalyst for hydrogen production in 1 m KOH. An alkaline electrolyzer is constructed using NiFeOx and NiFe-P coated iron foams as anode and cathode, which can realize overall water splitting with a current density of 100 mA cm−2 at an overpotential of 630 mV. By the spontaneous galvanic replacement reaction, the low-cost iron foam is used as an ideal 3D electrode substrate for fabrication of integrated bimetallic or even trimetallic electrocatalysts for both oxygen and hydrogen evolution reactions, which offers significant advantages of simplicity and zero energy consumption. An alkaline electrolyzer combining both electrode materials is constructed to realize efficient overall water splitting.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/aenm.201700107

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