Efficient Hydrogenation of Phenanthrene Enabled by d-Orbital Restructuring: A DFT Study

To address the challenge of activity degradation in pure Ni catalysts during phenanthrene hydrogenation, this study constructed bimetallic NinM(111) (M = Co, Cu, Zn) surfaces, namely NiCo(111), NiCu(111), NiZn(111), Ni3Co(111), Ni3Cu(111), and Ni3Zn(111). The reaction mechanism for the hydrogenation of phenanthrene to cis-syn-cis-perhydrophenanthrene was systematically investigated on these six NinM(111) surfaces. Subsequently, the electronic structures of the six surfaces were analyzed. The results indicate that introducing a second metal M induces d-d orbital hybridization between Ni and M, leading to the reconstruction of the 3d orbitals on the NinM(111) surface. Compared with the pure Ni(111) surface, the active 3d orbital (dz2) on the NinM(111) surface shifts downward overall. Through this continuous modulation strategy, the frontier orbital energy gap of the activated phenanthrene molecule can be progressively tuned. Among the screened catalysts, the Ni3Co(111) surface demonstrates the best hydrogenation activity and selectivity toward cis-syn-cis-perhydrophenanthrene. This study provides valuable insights for the rational design of efficient phenanthrene hydrogenation catalysts.