The transition from homogeneous to heterogeneous synthetic chemistry enabled by nanocatalysts necessitates investigations of the reaction mechanism and structure-activity relationships for inorganic nanoparticles and organic substrates. Herein, we report that hydrothermally synthesized ruthenium nanoparticles performed differently in the Se–Se bond activation and selenylation of heterocycles, exhibiting a volcano-shaped relationship between catalytic activity and composition. A synergistic effect was observed for Ru-RuO_x nanocatalysts, with numerous characterizations and density functional theory (DFT) calculations suggesting that a PhSeSePh molecule can initially be adsorbed on the metallic Ru sites and cleaved into two PhSe* species, which subsequently migrate to RuO_x sites and react with the nucleophile to achieve the selenylation of heterocycles.

Alloy nanocrystals (NCs) of Pt with 3d transition metals, especially Ni, are excellent catalysts for the oxygen reduction reaction (ORR). In this work, we, for the first time, demonstrated the water phase colloidal synthesis of Pt-M (M = Ni, Co and Fe) alloy NCs with tunable composition and morphology through a facile hydrothermal method. Pt-Ni alloy NCs synthesized with this method presented better ORR activity than commercial Pt/C catalysts. The X-ray energy dispersive spectra (EDS) mapping technique revealed that Pt-enriched shells existed on the as-synthesized Pt-Ni alloy NCs. About two atom thick layered Pt-enriched shells formed on Pt₅₀Ni₅₀ NCs and the thickness of the Pt-enriched shells increased as the Ni content increased. Furthermore, X-ray photoelectron spectroscopy analysis revealed that the oxidation level of the surface Pt atoms on the Pt-Ni alloy NCs decreased compared with monometallic Pt NCs, implying a decrease in the oxophilicity of the surface Pt atoms. Pt-Ni alloy NCs with lower oxophilicity of the surface Pt atoms give higher ORR activity. The most active alloy sample showed 13 times higher specific activity and six times higher mass activity at 0.9 V vs. a reversible hydrogen electrode when compared with commercial Pt/C. Pt-Ni alloy NCs also showed better durability than commercial Pt/C in long term ORR tests.