Insights into size effects of Pt/Al₂O₃ catalysts on hydrogen production from methylcyclohexane dehydrogenation

Liquid organic hydrogen carriers (LOHCs) have been considered as a promising technique for hydrogen storage and transportation. In this study, we investigated the impacts of Pt size on the catalytic performance of Pt/Al₂O₃ catalysts for the abstraction of H₂via dehydrogenation of methylcyclohexane (MCH), one of the most desired LOHC candidates. As the Pt loading increases from 0.05% to 5%, Pt species transition from nanoclusters to well-defined nanoparticles with the Pt size increasing from ∼0.7 nm to 1.7 nm. During MCH dehydrogenation, the turnover frequency (TOF) displays a volcano dependence on the Pt size, as the 0.1% Pt/Al₂O₃ sample with medium Pt size exhibits the highest atomic efficiency. Furthermore, the catalyst stability of Pt/Al₂O₃ samples is also dependent on the Pt size with the small Pt size in the 0.05% Pt/Al₂O₃ sample leading to fast catalyst deactivation due to the accumulation of coke on the Pt active sites. In summary, this study underscores the importance of Pt size to the activity and stability of Pt/Al₂O₃ in MCH dehydrogenation, providing new insights into the catalyst design for LOHC applications.