Plasma Pretreatment of Pt Single-Atom Precursors Supported on Mechanically Activated Al <sub>2</sub> O <sub>3</sub> : Enhanced Performance in Propane Dehydrogenation
Jingyi Yang, Eduardo Ortega, Joonbaek Jang, Andrea Martini, Jie Zhu, Janis Timoshenko, Jacopo De Bellis, Ferdi Schüth, Shamil Shaikhutdinov, Beatriz Roldán Cuenya
Abstract
High Resolution Image Download MS PowerPoint Slide We investigated the effect of catalyst pretreatment with “cold” plasmas on the catalytic performance of Pt single-atom catalyst (SAC) precursors supported on Al 2 O 3 for the propane dehydrogenation reaction. We found that the catalysts treated with a hydrogen plasma before the conventional calcination/reduction steps showed considerably increased propane conversion without loss of selectivity, whereas exposure to an argon plasma did not result in such an effect. Moreover, the H 2 plasma-treated catalyst showed a lower deactivation rate, suggesting better long-term stability. The structural and chemical evolution of the catalysts studied by TEM, XAS, XPS, and DRIFTS showed that the H 2 plasma: (i) partially reduces singly dispersed Pt 2+ species and promotes Pt clustering; (ii) decreases the amount of Cl remaining after the use of the hexachloroplatinic acid precursor; and (iii) enhances surface defects in the alumina support. We propose that the promotional effect of the H 2 plasma lies in the specific modification of the alumina surface, which in turn alters the metal-support interaction and leads to the formation of a more active Pt/Al 2 O 3 interface during the subsequent oxidation and reduction steps. The results show that nonthermal plasma treatments of single-atom precursors can become a tool for tuning the catalytic performance of highly dispersed metal catalysts.