Co-Exfoliated Noble-Metal Chalcogenide/Graphene Hybrids for Electrocatalytic Water Splitting

Two-dimensional (2D) materials and their heterostructures have been proven effective in energy applications such as energy storage (supercapacitors, batteries) and catalysis. Among them, Pt-based Transition Metal Dichalcogenides (TMDs) have been reported to have promising performance in Hydrogen Evolution Reaction (HER) [1]. However, their use remains limited mainly due to the high cost of using Pt. In this work, we will fabricate graphene-based hybrid heterostructures with different Pt-based TMDs. Graphene hybrids are also potential candidates for HER [2], and through their use, the amount of Pt can be reduced while tuning physical properties and catalytic behavior. Density functional theory calculations imply a strong interaction between the graphene and PtX₂ (X = S, Se, Te) heterostructures, much larger than the interaction of MoS₂/graphene heterostructure. A band-gap opening was observed in all cases. Calculating the adsorption energy of H₂ molecules in different adsorption sites of heterostructures implied a promising performance in water splitting. The hybrid nanostructures were fabricated with a single-step liquid-phase co-exfoliation procedure, which is a cost-effective procedure that also offers the possibility of industrial scalability [3],[4]. The fabricated hybrid inks presented an improved yield and long-term stability over a year, in comparison with the isolated dispersions of graphene and PtX₂. Transmission and scanning-transmission electron microscopy (TEM/STEM) observations revealed the morphological features of the exfoliated flakes, with graphene to be decorated with the Pt-based TMDs. STEM-EDX mapping confirmed the presence of all involved elements in all cases. UV-vis and Raman spectroscopies revealed the optical properties of the hybrid systems, which are modified concerning the individual materials. Finally, the performance of 2D inks in HER was evaluated, resulting in lower overpotential values. A comparative study was conducted on the effect of different chalcogen on the hybrid structures.<br/><br/><b>References</b><br/>[1] Chia X. et al., Layered Platinum Dichalcogenides (PtS₂, PtSe₂, and PtTe₂) Electrocatalysis: Monotonic Dependence on the Chalcogen Size, Advanced Functional Materials, <b>26</b> (2016)<br/>[2] Bonaccorso F. et al., Graphene, related two-dimensional crystals, and hybrid systems for energy conversion and storage, Science, <b>347</b> (2015)<br/>[3] Nicolosi V. et al., Liquid Exfoliation of Layered Materials. Science,<i> </i><b>340 </b>(2013)<br/>[4] Coelho J. et al., Manganese oxide nanosheets and a 2D hybrid of graphene–manganese oxide nanosheets synthesized by liquid-phase exfoliation, 2D Materials, <b>2</b>, (2015)