Pt Catalysts Supported on H2 and O2 Plasma-Treated Al2O3 for Hydrogenation and Dehydrogenation of the Liquid Organic Hydrogen Carrier Pair Dibenzyltoluene and Perhydrodibenzyltoluene

Dibenzyltoluene (DBT) is a promising liquid organic hydrogen carrier (LOHC) with theoretical 6.2 wt % hydrogen storage capacity which can be coupled with a renewable energy power generation system. In this work, the surface hydroxyl groups and surface oxygen vacancies (SOVs) on alumina were modified by a convenient and environmentally friendly plasma treatment method. Different Pt/Al2O3 catalysts were prepared via impregnation of the treated alumina, and the effects of different surface hydroxyl groups and SOVs on their reactivity for the reversible hydrogenation and dehydrogenation of DBT were investigated. The results show that SOVs increased after H2 plasma treatment, whereas the surface hydroxyl groups increased and SOVs decreased after O2 plasma treatment. Both the surface hydroxyl group and SOV can improve Pt metal dispersion. The more interesting observation is that the hydroxyl groups promote hydrogen spillover and the proportion of Pt(0), which not only benefit the catalyst hydrogenation and dehydrogenation activity but also reduce side reactions and increase long-term cycle performance. However, increased SOVs increased the fraction of low coordinated Pt which reduces the long-term cycle performance of the catalyst. As a result, increasing surface hydroxyl groups and appropriately reducing SOVs on Pt/Al2O3 are propitious for improving both reactivity and long-term cycle performance when using DBT as a LOHC.