Synergistic Roles of Single Co Atoms and Co Nanoparticles for the Hydrodeoxygenation and Ring Hydrogenation Reactions

Because of the highly inert aromatic ring, the hydrodeoxygenation and subsequent ring hydrogenation reactions of aromatic ketones into high-energy-density liquid hydrocarbons remain a great challenge even over noble metal catalysts. Herein, the heterogeneous cobalt catalysts composed of metallic Co nanoparticles and single Co atoms with Co–N5 motifs were found to display excellent activity in the simultaneous hydrodeoxygenation of C═O/C–OH bonds as well as the hydrogenation of the aromatic ring into high-energy-density liquid hydrocarbons, where single Co atoms served as the Lewis acid sites to activate the C═O/C–OH bonds as well as the aromatic ring, and metallic Co nanoparticles activated H2 molecules. Experimental data as well as DFT calculation further revealed that the single Co atoms activated the inert aromatic ring by changing the electron density of each carbon in the aromatic ring and thus facilitated the hydrogenation of the aromatic ring with a much lower energy barrier (1.14 vs 1.96 eV without the single Co atom sites).