Reaction of H₂ with polyoxometalate supported Rhodium(0) and Iridium(0) nanoparticles in aqueous suspensions: a kinetic study

The kinetics of the reactions of H₂ with rhodium and iridium nanoparticles (NPs), in aqueous suspensions, were studied by following their catalytic reduction of PW₁₂O₄₀³⁻, POM. The reaction of H₂ with the same size (∼2.5 nm) of two different nanoparticles was carried out to check how the nature of the nanoparticles affects the reaction kinetics. Herein we report the first kinetic measurement of H₂ + Rh⁰ and Ir⁰ NPs in the absence of an electric field. A comparison of the apparent rate constants of the reactions Rh⁰-NPs and Ir⁰-NPs + H₂ to the previously reported Pt⁰-NPs + H₂ indicates that the rates decrease along the series k(Pt) > k(Rh) > k(Ir), though they are of the same order of magnitude. The adsorption of hydrogen and/or H atom can affect the structure of the M⁰-NPs.