Nature of Hydrogen Adsorption on Platinum in the Aqueous Phase

The thermodynamic state of H₂ adsorbed on Pt in the aqueous phase was determined by kinetic analysis of H₂ reacting with D₂O to HDO, HD and D₂ and by DFT based ab inito molecular dynamic simulation of H2 adsorption on Pt (111), Pt (110), and Pt nanoparticles. Dissociative adsorption of H₂ on Pt is significantly weakened in the aqueous phase compared to adsorption at gas‐solid interface. Water destabilizes adsorbed H, decreasing the heat of adsorption by 19 − 22 kJ/mol(H₂), while inducing an additional entropy loss of 50 − 70 J/(mol(H₂)·K). Upon dissociative H₂ adsorption, the averaged distance of water from the Pt surface increases and it assumes a more ordered structure. In turn, the more ordered water layer limits the translation mobility of adsorbed H. The presence of hydrated hydronium ions next to Pt further reduces the H‐Pt bond strength.

from A via a.sfakia on Inoreader https://ift.tt/2GqD4IJ