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 nC₆₀

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 (η₁₀) 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 η₁₀ 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.