Atomic-Scale insights into hybridization and synergistic Catalysis of Ni-MoS2 and 2Ni-MoS2 for hydrocracking phenanthrene: A comprehensive study of Citric Acid-Directed NiS2 and MoS2 for selective Short-Chain monoaromatics and Malic Acid-Directed Ni-MoS2 and 2Ni-MoS2 for selective long-chain monoaromatics

Abstract

This study explores the ligand-directed synthesis of NiS₂, MoS₂, Ni-MoS₂, and 2Ni-MoS₂ using citric acid (CA) and malic acid (MA) as ligands, supported by experimental results and density functional theory (DFT) calculations. CA was employed to prepare isolated NiS₂ and MoS₂, while MA facilitated the formation of bimetallic Ni-MoS₂ and 2Ni-MoS₂. The catalysts were evaluated for their performance in the hydrocracking of Phenanthrene (PHE), revealing distinct product selectivity. Isolated NiS₂ and MoS₂ predominantly produced short-chain monoaromatic products due to limited hydrogen spillover and strong binding of intermediates, whereas Ni-MoS₂ and 2Ni-MoS₂ selectively formed long-chain monoaromatics, driven by enhanced hydrogen spillover, synergistic Ni-Mo interactions, and improved intermediate stabilization.

DFT calculations provided insights into the ligand effect on electronic structures and catalytic properties. CA-derived NiS₂ and MoS₂ exhibited strong binding at active sites but limited dynamic interactions, while MA-derived Ni-MoS₂ and 2Ni-MoS₂ demonstrated moderate adsorption energies and efficient charge transfer, favoring selective hydrogenation and bond cleavage. These findings highlight the critical role of ligand choice in tailoring the structural and electronic properties of catalysts, offering a rational design strategy for optimizing hydrocracking processes and achieving desired product distributions.