Ni/Al₂O₃ structures on defective carbon coating derived from pyrolysis of nitrogen-enriched coal tar pitch for acetylene hydrogenation

The development of catalysts with both high activity and superior selectivity for the selective C₂H₂ hydrogenation remains a substantial challenge in catalysis. In this work, we successfully synthesized a series of Ni/Al₂O₃ samples coated with nitrogen-doped carbon (NC) containing C defects through a hydrothermal approach. The Ni/Al₂O₃@NC achieved 98% C₂H₂ conversion and 97% C₂H₄ selectivity. This excellent performance is attributed to the synergistic effects of NC defects and the controlled thickness of the NC layer. The NC coating not only promotes uniform dispersion of Ni nanoparticles but also modulates the electronic structure of the active metal through strong metal-support interactions. Additionally, the NC layer facilitates H₂ diffusion while hindering C₂H_y species, thereby enhancing both activity and selectivity. Theoretical simulations reveal that defects reduce the energy barrier of the rate-determining step, promoting the formation of the C₂H₃^⁎ intermediate. Furthermore, the defects enhance electron transfer from the Ni to NC layer surface, strengthening the adsorption of key intermediates. This work presents a facile and efficient strategy for designing cost-effective, non-precious metal catalysts for highly selective C₂H₂ hydrogenation.