Mechanistic insights into interfacial nano-synergistic effects in trimetallic Rh-on-NiCo on-CNTs for room temperature solvent-free hydrogenations

Mono- and bimetallic nanoparticles (NPs) supported on carbon nanotubes (CNTs) (Ni/CNTs, Co/CNTs and NiCo/CNTs) were synthesized at room temperature (RT) via hydrazine hydrate reduction method without any surfactant. The galvanic replacement reaction was exploited to prepare Rh/Ni/CNTs, Rh/Co/CNTs and Rh/NiCo/CNTs supported nanocatalysts. Prepared nanocatalysts were extensively characterized using an array of advanced analytical techniques. The catalytic performance of the catalysts was evaluated in the hydrogenation of tetralin. Reduced Rh/NiCo/CNTs catalyst (Rh-on-NiCo NP) exhibited high catalytic activity at RT, significantly improved as compared to Rh/Ni/CNTs and Rh/Co/CNTs due to the interfacial nano-synergy effect among different metallic related species (Rh, Ni and Co). In-situ XAS results confirmed the mechanism of the interfacial nano-synergy effect, wherein Rh sites provided activated hydrogen species (H*), and H* was subsequently transferred to the surface of NiCo NPs; while tetralin was adsorbed and activated at NiCo sites, reacting with H* to produce decalin. The present work proposed a novel strategy to design highly efficient and stable multimetallic catalysts for heterogeneous catalytic hydrogenation reactions.