Kinetics of the reaction of H₂with Pt-nanoparticles in aqueous suspensions monitored by the catalytic reduction of PW₁₂O₄₀^3-

The reaction between Pt and H2 is very fast and essential in many catalytic processes, but until now, the rate constants of this reaction were measured only electrochemically. Herein we report the first kinetic measurements of H2 + Pt nanoparticles, Pt-NPs, in the absence of an electric field. The reaction of H2 with two different sized Pt-nanoparticles (2.0 and 4.0 nm) stabilized by a monolayer of PW12O403- was studied by following the rate of formation of PW12O404-/5-. The observed reaction rate depends linearly on [Pt-NPs] and on [H2] but is independent on [PW12O403-]. The results indicate that the rate-determining step is either Pt-NP-H2 ? Pt-NP-2H or Pt-NP-H2 ? (Pt-NP-H)- + H3O+. The rate constants of the latter two reactions decrease with the increase of hydrogen coverage of the Pt-NPs.