The Chemical Properties of Hydrogen Atoms Adsorbed on M⁰Nanoparticles Suspended inAqueous Solutions: The Case of Ag⁰-NPs and Au⁰-NPs Reduced by BD₄

The nature of H-atoms adsorbed on M⁰-nanoparticles is of major importance in many catalyzed reduction processes.Using isotope labeling,wedetermined that hydrogen evolution from transient {(M⁰-NP)-H_n}ⁿ proceeds mainly via the Heyrovsky mechanism when nislarge (i.e., the hydrogens behave as hydrides) but mainly via the Tafel mechanism when nissmall (i.e., the hydrogens behave as atoms). Additionally, the relative contributions of the two mechanisms differ considerably for M = Au and Ag. The results are analogous to those recently reported for the M⁰-NP-catalyzed de-halogenation processes.