Mauro Pasta

Mechanochemical grinding of polycrystalline powders of the Prussian blue analogue (PBA) Mn[Co(CN)6]2/3□1/3·xH2O and K3Co(CN)6 consumes the latter and chemically modifies the former. A combination of inductively-coupled plasma and X-ray powder diffraction measurements suggests the hexacyanometallate vacancy fraction in this modified PBA is reduced by approximately one third under the specific conditions we explore. We infer the mechanochemically-driven incorporation of [Co(CN)6]3- ions onto the initially-vacant sites, coupled with intercalation of charge-balancing K+ ions within the PBA framework cavities. Our results offer a new methodology for the synthesis of low-vacancy PBAs.

Copyright © 2020 American Chemical Society. Two-dimensional (2D) molybdenum disulfide (MoS2) has excellent electrocatalytic behavior for the hydrogen evolution reaction (HER), where the catalysis of 2H phase originates from its edges, defects, and strains. Most synthetic methods to activate the electrochemically inert basal planes with catalytic active metals are completed by sequential steps. However, this is extremely time-consuming and lacks production scalability. Herein, we develop a one-step strategy to achieve efficient electrocatalyst of Pt:MoS2 hybrid utilizing atmospheric pressure chemical vapor deposition synthesis on a conductive glassy carbon (GC) plate that can be directly employed as the working electrode in the HER. The monolayer thickness ensures decreased interlayer electron hopping and increased efficiency of the charge transfer from the electrode. We tune the domain morphology by controlling the precursor flux to enter kinetic or thermodynamic growth regime, delivering dendritic or triangular shape. The materials chemistry undertaken provides fundamental insights into the instability of Pt as metal substitutional dopants in the MoS2 lattice, and instead the stable configuration observed is with Pt as highly dispersed small nanocrystals and single atoms bound to the MoS2 surface. The Pt functionalization at a reduced loading level modulates the favorable HER pathway and triggers synergies in the cocatalyst, which exhibits an onset potential of 48 mV, a Tafel slope of 46 mV dec-1, and an exchange current density of 110 μA cm-2. The enriched edges and defects of dendrite endow it superiority to the triangle, with regard to the density of catalytic sites and synergistic effects along with electrical resistance. These underpin the positive role of a large dendritic MoS2 monolayer as a Pt scaffold in water electrolysis.