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. 2018 Jan 24;4(1):112-119.
doi: 10.1021/acscentsci.7b00502. Epub 2017 Dec 7.

When NiO@Ni Meets WS2 Nanosheet Array: A Highly Efficient and Ultrastable Electrocatalyst for Overall Water Splitting

Dewen Wang  1   2 , Qun Li  1   2 , Ce Han  1 , Zhicai Xing  1 , Xiurong Yang  1
Affiliations

When NiO@Ni Meets WS2 Nanosheet Array: A Highly Efficient and Ultrastable Electrocatalyst for Overall Water Splitting

Dewen Wang et al. ACS Cent Sci. .

Abstract

The development of low-cost, high-efficiency, and stable bifunctional electrocatalysts toward the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is of paramount importance for large-scale water splitting. Here, we develop a new strategy for the first design and synthesis of a NiO@Ni decorated WS2 nanosheet array on carbon cloth (NiO@Ni/WS2/CC) composite. This composite serves as a unique three-dimensional (3D) synergistic electrocatalyst that not only combines the intrinsic properties of individual NiO@Ni and WS2, but also exhibits significantly improved HER and OER activities when compared to that of pure NiO@Ni and WS2. This electrocatalyst possesses Pt-like activity for HER and exhibits better OER performance than that for commercial RuO2, as well as demonstrating superior long-term durability in alkaline media. Furthermore, it enables an alkaline electrolyzer with a current density of 10 mA cm-2 at a cell voltage as 1.42 V, which is the lowest one among all reported values to date. The excellent performance is mainly attributed to the unique 3D configuration and multicomponent synergies among NiO, Ni, and WS2. Our findings provide a new idea to design advanced bifunctional catalysts for water splitting.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Figure 1
Figure 1
Schematic illustration of the preparation procedure for the NiO@Ni/WS2/CC.
Figure 2
Figure 2
(A) XRD pattern of NiO@Ni/WS2/CC. (B) Raman spectra of Ni/WS2/CC, NiO/WS2/CC, and NiO@Ni/WS2/CC. SEM images of (C, D) WS2/CC and (E, F) NiO@Ni/WS2/CC. (G) TEM image of one single NiO@Ni/WS2 nanosheet. (H) HRTEM image taken from the NiO@Ni/WS2 nanosheet. (I) EDX elemental mapping images of an individual NiO@Ni/WS2 nanosheet.
Figure 3
Figure 3
(A) The XANES spectra of Ni K-edge. (B) The Fourier transforms of k3-weighted Ni K-edge EXAFS spectra for NiO@Ni/WS2/CC, Ni foil and NiO. (C) Observed (black line) and calculated (red and blue line) Fourier transforms of k3-weighted Ni K-edge EXAFS spectra for NiO@Ni/WS2/CC. (D) The XANES spectra of W K-edge. (E) Fourier transforms of k3-weighted W K-edge EXAFS spectra for WS2/CC and NiO@Ni/WS2/CC. (F) The XANES spectra of Ni K-edge for WS2/CC and NiO@Ni/WS2/CC.
Figure 4
Figure 4
(A) The LSV curves for NiO@Ni/WS2/CC, WS2/CC, Pt/C/CC, and NiO@Ni/CC with a scan rate of 5 mV s–1 for HER. (B) The corresponding Tafel plots. (C) LSV curves for NiO@Ni/WS2/CC initially, after 500 and 1000 CV cycles. (D) Potentiostatic electrolysis of NiO@Ni/WS2/CC for 40 h with a scan rate of 5 mV s–1.
Figure 5
Figure 5
(A) LSV curves for NiO@Ni/WS2/CC, RuO2/CC, and NiO@Ni/CC with a scan rate of 5 mV s–1 for OER. (B) The corresponding Tafel plots of NiO@Ni/WS2/CC, RuO2/CC, and NiO@Ni/CC. (C) Chronopotentiometric curve of NiO@Ni/WS2/CC with constant current density of 50 mA cm–2. (D) LSV curves of water electrolysis for NiO@Ni/WS2/CC∥NiO@Ni/WS2/CC, RuO2/CC∥Pt/C/CC, and NiO@Ni/CC∥NiO@Ni/CC with a scan rate of 2 mV s–1.
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