A new strategy to transform mono and bimetallic non-noble metal nanoparticles into highly active and chemoselective hydrogenation catalysts

A new strategy to transform non-noble metal oxide nanoparticles (NPs) into highly active and selective metallic NPs as hydrogenation catalysts by a simple carbon coating process based on hydrothermal treatment with glucose is presented. During the carbon coating process, metal oxide NPs will be reduced to metallic NPs and covered by thin carbon layers, resulting in formation of Metal@C NPs. Through this method, monometallic Co@C has been prepared, which shows excellent activity and selectivity for chemoselectivity hydrogenation of substituted nitroarenes to corresponding anilines under mild conditions. Kinetic, isotopic and spectroscopic studies indicate that hydrogen dissociation-addition is the controlling step in chemoselective hydrogenation reaction with Co@C NPs. Stabilization and the reaction rate of metallic Co are improved by preparing bimetallic CoNi@C catalyst, leading to almost fivefold improved activity. Our preparation method enables to synthesize non-noble bimetallic CoNi@C nanoparticles with nearly one-order magnitude higher activity than any Co-based non-noble metal catalysts prepared by other methods, without necessity to involve the promoting role of metal-N interactions. At last, we also show the application of Co@C NPs for hydrogenation of levulinic acid to γ-valerolactone.