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 C 2 H 2 hydrogenation remains a substantial challenge in catalysis. In this work, we successfully synthesized a series of Ni/Al 2 O 3 samples coated with nitrogen-doped carbon (NC) containing C defects through a hydrothermal approach. The Ni/Al 2 O 3 @NC achieved 98% C 2 H 2 conversion and 97% C 2 H 4 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 H 2 diffusion while hindering C 2 H 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 C 2 H 3 ⁎ 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 C 2 H 2 hydrogenation. • By utilizing readily available and cost-effective coal tar pitch as the source of carbon and nitrogen, we successfully synthesized Ni/Al₂O₃@NC samples with varying carbon layer thicknesses, achieving 98% C₂H₂ conversion and 97% C₂H₄ selectivity. • Combining characterization and computational data revealed the structure-activity relationship of Ni/Al₂O₃@NC. Ni donates electrons to the nitrogen-doped carbon layer, activating it and enhancing adsorption of C 2 H 2 ⁎ and C 2 H 3 ⁎ . • The defects generated during asphalt pyrolysis significantly lower the energy barrier of the rate-limiting step, facilitating C 2 H 4 ⁎ production and enhancing selectivity. • DFT analysis uncovers carbon layer defects functioning as selective pathways for H₂ and H ⁎ , enhancing hydrogen dissociation by blocking C 2 H y ⁎ molecules.