Tungsten
disulfide (WS2) is well known to have great
potential as an electrocatalyst, but the practical application is
hampered by its intrinsic inert plane and semiconductor properties.
In this work, owing to a Co-based zeolite imidazole framework (ZIF-67)
that effectively inhibited WS2 growth, few-layered WS2 was confined to the surface of Co, N-doped carbon polyhedron
(WS2@Co9S8), with more marginal active
sites and higher conductivity, which promoted efficient oxygen evolution
reaction (OER) and hydrogen evolution reaction (HER). For the first
time, WS2@Co9S8 was prepared by mixing
in one pot of a liquid phase and calcination, and WS2 realized
uniform distribution on the polyhedron surface by electrostatic adsorption
in the liquid phase. The obtained hybrid catalyst exhibited excellent
OER and HER catalytic activity, and the OER potential was only 15
mV at 10 mA cm–2 higher than that of noble metal
oxide (RuO2). The improvement of catalytic activity can
be attributed to the enhanced exposure of sulfur edge sites by WS2, the unique synergistic effect between WS2 and
Co9S8 on the metal–organic framework
(MOF) surface, and the effective shortening of the diffusion path
by the hollow multi-channel structure. Therefore, the robust catalyst
(WS2@Co9S8) prepared by a simple
and efficient synthesis method in this work will serve as a highly
promising bifunctional catalyst for OER and HER.
The rational design and preparation of a heterogeneous electrocatalyst for hydrogen evolution reaction (HER) has become a research hotspot, while applicable and pH-universal tungsten disulfide (WS 2 )-based hybrid composites are rarely reported. Herein, we propose a novel hybrid catalyst (WS 2 / Co 9 S 8 /Co 4 S 3 ) comprising two heterojunctions of WS 2 /Co 4 S 3 and WS 2 /Co 9 S 8 , which grow on the porous skeleton of Co, N-codoped carbon (Co/NC) flexibly applicable to all-pH electrolytes. The effect of double heterogeneous coupling on HER activity is explored as the highly flexible heterojunction is conducive to tune the activity of the catalyst, and the synergistic interaction of the double heterojunctions is maximized by adjusting the proportion of heterojunction components. Theoretical calculations show that both WS 2 /Co 9 S 8 and WS 2 /Co 4 S 3 heterojunctions have a Gibbs free energy of H reaction (|ΔG H* |) close to 0.0 eV and a facile decomposition water barrier. As collective synergy of dual Co x S y -modified WS 2 double heterojunction, WS 2 /Co 9 S 8 /Co 4 S 3 greatly enhances HER activity compared to bare Co 9 S 8 /Co 4 S 3 or single heterojunction (WS 2 /Co 9 S 8 ) in all-pH media. Besides, we have elucidated the unique HER mechanism of the double heterojunction to decompose H 2 O and confirm its excellent activity under alkaline and neutral conditions. Thus, this work provides new insights into WS 2 -based hybrid materials potentially applied to sustainable energy.
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