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A Co-doped Ni–Fe mixed oxide mesoporous nanosheet array with low overpotential and high stability towards overall water splitting

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Abstract

The construction of bifunctional water splitting electrocatalysts with new and optimized chemical compositions and structures for promoting the efficiencies of both half-reactions of the water splitting process, that is, the anodic oxygen evolution reaction (OER) and cathodic hydrogen evolution reaction (HER), represents a great advancement. Herein, a Co-doped NiO/NiFe2O4 mixed oxide mesoporous nanosheet array on Ni foam with controllable composition and morphology is constructed as a bifunctional electrocatalyst by a facile solvothermal synthesis method using methanol as a solvent and a reactant, followed by annealing in air. The well-connected mesoporous nanosheet array provides a large number of catalytically active sites and buffers the large volume changes that occur during the electrochemical process. Moreover, NiFe2O4 has a catalytic active phase that plays a significant role in improving the catalytic activity, and Co2+ doping in NiO/NiFe2O4 can increase the conductivity and activate the Ni sites at lower overpotentials via charge transfer effects. As a result, the optimized Co-doped NiO/NiFe2O4 mixed oxide mesoporous nanosheet array Co6.25Fe18.75Ni75Ox exhibits excellent OER activity with a small overpotential of 186 mV at 10 mA cm−2 and a low Tafel slope of 38.5 mV dec−1. It also presents outstanding HER activity, only requiring a small overpotential of 84 mV to deliver 10 mA cm−2, along with a low Tafel slope of 53.6 mV dec−1. Moreover, this Co6.25Fe18.75Ni75Ox electrode remains stable for 1000 cyclic voltammogram cycles and 12 hours of galvanostatic measurements in both OER and HER. A two-electrode electrolyzer using bifunctional Co6.25Fe18.75Ni75Ox as both the anode and cathode demonstrates active and stable overall water splitting performance with a cell voltage of only 1.583 V at 10 mA cm−2. This study explores multimetal Ni–Fe mixed oxide as an efficient bifunctional electrocatalyst for overall water electrolysis.

Graphical abstract: A Co-doped Ni–Fe mixed oxide mesoporous nanosheet array with low overpotential and high stability towards overall water splitting

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Publication details

The article was received on 10 Sep 2017, accepted on 21 Nov 2017 and first published on 22 Nov 2017


Article type: Paper
DOI: 10.1039/C7TA07956G
Citation: J. Mater. Chem. A, 2018, Advance Article
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    A Co-doped Ni–Fe mixed oxide mesoporous nanosheet array with low overpotential and high stability towards overall water splitting

    Z. Wu, X. Wang, J. Huang and F. Gao, J. Mater. Chem. A, 2018, Advance Article , DOI: 10.1039/C7TA07956G

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