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.
