Non-noble metal catalysts for hydrogenation: A facile method for preparing Co nanoparticles covered with thin layered carbon

•Metallic Co nanoparticles covered by thin carbon layers are prepared.•Metallic Co is the active phase for hydrogenation reaction.•The role of carbon layers is to protect Co nanoparticles from overoxidation.•Surface properties of Co nanoparticles affect the chemoselectivity.

Metallic cobalt nanoparticles with surface CoOx patches covered by thin layered carbon (named Co@C) have been directly synthesized by thermal decomposition of Co-EDTA complex. Raman spectra and HRTEM images suggest that discontinuities can be found in the disordered layered carbon. XPS shows that the CoOx patches in the Co@C nanoparticles can reduced to metallic Co by H2 under reaction conditions (7 bar at 120 °C), and H2–D2 exchange experiments show that the reduced metallic Co nanoparticles covered by carbon layers can dissociate H2. The Co@C nanoparticles show excellent activity and selectivity during chemoselective hydrogenation of nitroarenes for a wide scope of substrates under mild reaction conditions. Based on the results from DRIFTS adsorption experiments, we propose that metallic Co in the Co@C nanoparticles is the active phase. The role of the carbon layers is to protect the Co from overoxidation by air, leading to the chemoselective hydrogenation of nitroarenes.

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