Kinetics of the reaction of H2 with Pt0-nanoparticles in aqueous suspensions monitored by the catalytic reduction of PW12O403−

Abstract

The reaction between Pt⁰ 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 + Pt⁰ nanoparticles, Pt⁰-NPs, in the absence of an electric field. The reaction of H₂ with two different sized Pt⁰-nanoparticles (2.0 and 4.0 nm) stabilized by a monolayer of PW₁₂O₄₀³⁻ was studied by following the rate of formation of PW₁₂O₄₀^4−/5−. The observed reaction rate depends linearly on [Pt⁰-NPs] and on [H₂] but is independent on [PW₁₂O₄₀³⁻]. The results indicate that the rate-determining step is either Pt⁰-NP-H₂ → Pt⁰-NP-2H or Pt⁰-NP-H₂ → (Pt⁰-NP-H)⁻ + H₃O⁺. The rate constants of the latter two reactions decrease with the increase of hydrogen coverage of the Pt⁰-NPs.