An in Situ Sulfidation Approach for the Integration of MoS2 Nanosheets on Carbon Fiber Paper and the Modulation of Its Electrocatalytic Activity by Interfacing with nC(60)
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2016 American Chemical Society. Molybdenum disulfide (MoS2) is a promising earth-abundant and low-cost electrocatalyst for the hydrogen evolution reaction (HER). In this study, we describe a stepwise synthetic approach comprising vapor transport, reduction, and topochemical sulfidation for creating 3D arrays of MoS2 nanosheets directly integrated onto carbon fiber paper (CFP) substrates. The sulfidation process results in a high density of edge sites along both the edges and the basal planes of MoS2. The obtained materials characterized by a high density of exposed edge sites exhibit promising electrocatalytic performance, including an overpotential (10) of 245 mV at 10 mA/cm2, a Tafel slope of 81 mV/dec, and a turnover frequency (TOF) of 1.28 H2/s per active site at -0.2 V vs RHE in a 0.5 M acidic solution. The electrocatalytic properties of the MoS2 nanosheets are observed to be substantially enhanced by interfacing with solution-deposited buckminsterfullerene nanoclusters (nC60). A coverage of ca. 2% of nC60 yields a hybrid electrocatalyst exhibiting an 10 value of 172 mV, a Tafel slope of 60 mV/dec, and a TOF value of 2.33 H2/s per active site at -0.2 V vs RHE. The enhancement of electrocatalytic activity is found to derive from interfacial charge transfer at nC60/MoS2 p-n heterojunctions. The high conductivity of the interfacial layer formed as a result of charge transfer from nC60 to MoS2 is thought to substantially mitigate the limitations imposed by the poor basal plane conductivity of undoped MoS2. The hybrid catalysts illustrate an important design principle involving the use of structured interfaces to enhance the catalytic activity of low-dimensional materials.
