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Synthesis of Surface Grown Pt Nanoparticles on Edge-Enriched MoS2 Porous Thin Films for Enhancing Electrochemical Performance

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journal contribution
posted on 2019-01-04, 18:28 authored by Sha Li, Ja Kyung Lee, Si Zhou, Mauro Pasta, Jamie H. Warner
A hybrid catalyst, Pt nanocrystals deposited on the surface of MoS2 vertically standing nanoplatelets, is synthesized via chemical vapor deposition and subsequent thermal annealing (TA) of Pt precursor. The hybrid material shows promising results as an electrocatalyst for the hydrogen evolution reaction (HER). By varying Pt synthesis conditionsprecursor loading and TA temperaturethe deposition sites, size, and morphology of the Pt nanostructure can be controlled. The size effect of a Pt nanoparticle on catalytic activity and sintering resistance is discussed. Results show that higher Pt loading yields better HER performance despite smaller specific surface area; higher TA temperature delivers larger average particle size of Pt crystals and lower HER activity. Larger average size leads to fast sintering and thus poor durability of the catalyst. On the basis of the correlation between HER performance and growth behaviors of Pt on MoS2 surfaces, an optimization route for a highly active and stable cocatalyst can be established. The optimized Pt-MoS2 catalyst (400 °C, 11 wt %) reported in this study possesses superior overpotential of 9 mV (close to zero), Tafel slope of 44 mV/dec, and moderate exchange current density of 373 μA/cm2; it exhibits activity degradation of 140 mV @ 20 mA/cm2 after 10 000 cycles. The Tafel slope indicates the combination of Volmer–Heyrovsky steps as HER mechanism in this particular hybrid catalyst system. The outstanding HER activity attributes to highly dispersed Pt nanoparticles grown on MoS2 basal surfaces, large MoS2 edge density, and Pt–S bonding effect induced activity improvement of MoS2 as well as 3D porous network assisted superaerophobic surface.