Synergistic Effect between Pt and CrO_<i>x</i> on Reversible Hydrogenation and Dehydrogenation of Dibenzyltoluene

Liquid organic hydrogen carriers are a safe and economic alternative for hydrogen storage and long-distance transport. A new dopant, CrOx, was developed and added to Pt/Al2O3, and the obtained catalysts exhibited higher performance of perhydro dibenzyltoluene (H18-DBT) dehydrogenation with the increasing CrOx amounts until 1 wt %. On the contrary, the performance of dibenzyltoluene (DBT) hydrogenation decreased with the increasing amount of CrOx. The degree of dehydrogenation was dramatically improved to 87.2% after adding 1 wt % CrOx compared to the unmodified Pt/Al2O3 catalyst (65.6%), and the hydrogenation activity was stable within ten cycles of reversible hydrogenation and dehydrogenation of DBT. With the increasing CrOx amounts, CrOx species aggregated to polychromates and then crystalline Cr2O3, leading to higher Pt electron density, smaller Pt particle size, and further, a higher dehydrogenation activity and lower hydrogenation performance. Polychromates were identified as important species for dehydrogenation.