Chinese Journal of Catalysis 40 (2019) 1576–1584
催化学报 2019年 第40卷 第10期 |
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j o u r n a l  h o m e p a g e : w w w.e l s e v i e r.c o m /l o c a t e /c h n j c
Article
In situ growth of minimal Ir-incorporated Co x Ni 1-x O nanowire arrays on Ni foam with improved electrocatalytic activity for overall water splitting
Xiaoli Li, Wenming Xue, Rong Mo *, Sui Yang, Hongxing Li #, Jianxin Zhong
minimalHunan Key Laboratory for Micro-Nano Energy Materials and Devices, School of Physics and Optoelectronics, Xiangtan University, Xiangtan 411105,  Hunan, China
A R T I C L E  I N F O
A B S T R A C T
Article history:
Received 28 April 2019 Accepted 30 May 2019 Published 5 October 2019
Exploration of cost-effective electrocatalysts for boosting the overall water-splitting efficiency is vitally important for obtaining renewable fuels such as hydrogen. Here, earth-abundant Co x Ni 1-x O nanowire arrays were used as a structural framework to dilute Ir incorporation for fabricating elec-trocatalysts for water splitting. Minimal Ir-incorporated Co x Ni 1-x O nanowire arrays were synthe-sized through the facile hydrothermal method with subsequent calcination by using Ni foam (NF) as both the substrate and source of Ni. The electrocatalytic water-splitting performance was found to crucially depend on the Ir content of the parent Co x Ni 1-x O nanowire arrays. As a result, for a minimal Ir content, as low as 0.57 wt%, the obtained Ir-Co x Ni 1-x O/NF electrodes exhibited optimal
catalytic activity in terms of a low overpotential of 260 mV for the oxygen evolution reaction and 53 mV for the hydrogen evolution reaction at 10 mA cm −2 in 1 mol L –1 KOH. When used as bifunctional elec-trodes in water splitting, the current density of 10 mA cm –2 was obtained at a low cell voltage of 1.55 V. Density functional theory calculations revealed that the Ir-doped Co x Ni 1-x O arrays exhibited en-hanced electrical conductivity and low Gibbs free energy, which contributed to the improved elec-trocatalytic activity. The present study presents a new strategy for the development of transition metal oxide electrocatalysts with low levels of Ir incorporation for efficient water splitting.
© 2019, Dalian Institute of Chemical Physics, Chinese Academy of Sciences.
Published by Elsevier B.V. All rights reserved.
Keywords:
Co x Ni 1-x O nanowire array Iridium incorporation Electrocatalyst Water splitting Overpotential
1.  Introduction
The depletion of fossil fuels and the associated serious en-vironmental problems are the motivations
for the intense re-search on new energy sources, including hydrogen [1–3]. As one of the most promising alternatives to fossil fuels, hydrogen exhibits a high energy density and is environmentally friendly [4–6]. Electrocatalytic water splitting, involving the hydrogen
(2H + + 2e – → H 2) and oxygen (2H 2O → O 2 + 4H + + 4e –) evolution reactions, is one of the most appealing approaches for extract-ing molecular hydrogen from water [7,8]. In these two electro-chemical reactions, the ideal free energy change, ∆G 0, for the conversion of one H 2O molecule into H 2 and 1/2 O 2 under standard temperature and pressure is 237.2 kJ mol –1, according to the Nernst equation, which corresponds to a reversible elec-trochemical cell voltage of 1.23 V [9]. However, to overcome
* Corresponding author. E-mail: morongstar@163 # Corresponding author. E-mail: hongxinglee@xtu.edu
This work was financially supported by the National Natural Science Foundation of China (51772255), the Hunan Provincial Innovation Foundation For Postgraduate (CX2017B274), the National Basic Research Program of China (2015CB921103), and the Program for Changjiang Scholars and Innovative Research Team in University (IRT13093).
DOI: S1872-2067(19)63414-5 | www.sciencedirect/science/journal/18722067 | Chin. J. Catal., Vol. 40, No. 10, October 2019

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