Few-Layered Trigonal WS<inf>2</inf>Nanosheet-Coated Graphite Foam as an Efficient Free-Standing Electrode for a Hydrogen Evolution Reaction
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© 2017 American Chemical Society. Few-layered tungsten disulfide (WS 2 ) with a controlled-phase ratio (the highest trigonal-phase ratio being 67%) was exfoliated via lithium insertion. The exfoliated WS 2 nanosheets were then anchored onto three-dimensional (3D) graphite foam (GF) to fabricate free-standing binder-free electrodes. The 3D GF can increase the interfacial contact between the WS 2 nanosheets and the electrolyte and facilitate ion transfer. Without the nonconductive binder, an intimate contact between the WS 2 and GF interface can be created, leading to the improvement of electrical conductivity. In comparison to the pure WS 2 nanosheets, the overpotential for a hydrogen evolution reaction is significantly decreased from 350 mV to 190 mV at 10 mA/cm 2 , and no deactivation occurs after 1000 cycles. The density functional theory computations reveal that the efficient catalytic activity of the trigonal-phase WS 2 /GF electrode is attributed to the lower Gibbs free energy for H* adsorption and higher electrical conductivity.