(544cg) Different Catalytic Behaviors of Pd and Pt Metals in Decalin Dehydrogenation to Naphthalene

The catalytic dehydrogenation of aromatic molecule has received a lot of attention for the application to hydrogen storage system. Among several Ï€-conjugated substrates for the so-called liquid “organic hydrides”, decalin is a very suitable molecule to be studied for catalytic activities in the dehydrogenation and hydrogenation reactions due to its high H₂ content of 7.3 wt.%. Owing to the endothermic nature of the dehydrogenation reaction, metal catalysts such as Pt or Pd have been widely used for the dehydrogenation reaction. However, mechanistic studies from theoretical or experimental approaches for the catalytic activity and selectivity are not still sufficient to understand the dehydrogenation reaction on these metal surfaces.

For this reason, we mechanistically investigated the entire reaction profile of catalytic dehydrogenation of decalin to tetralin or naphthalene on Pd(111) and Pt(111) surfaces through density functional theory (DFT) calculations. Our DFT results showed that the conversion of decalin to tetralin is energetically more preferred to the dehydrogenation reaction on Pt catalyst. On the other hand, Pd shows energetically more favored reaction pathway in the second dehydrogenation process where tetralin converts into naphthalene. These results are in good agreement with the following experiments in that decalin is more easily dehydrogenated over Pt/C while the dehydrogenation of tetralin is more facile over Pd/C. Based on our theoretical analysis, we elucidated that such different catalytic activity and selectivity between Pd and Pt originate from the different structural and chemical characteristics between Pd and Pt metals.