Plasma Pretreatment of Pt Single-Atom Precursors Supported on Mechanically Activated Al₂O₃: Enhanced Performance in...

We investigated the effect of catalyst pretreatment with "cold" plasmas on the catalytic performance of Pt single-atom catalyst (SAC) precursors supported on Al₂O₃ 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 H₂ 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 H₂ plasma: (i) partially reduces singly dispersed Pt²⁺ 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 H₂ 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/Al₂O₃ 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.