Ligand-coordinated supported catalysts (LCSCs) are of growing interest for heterogeneous single-atom catalysis. We investigate the effect of the choice of organic ligand on the activity and stability of supported single-atom Pt-ligand catalysts for ethylene hydrogenation. The activity of these catalysts shows a significant dependence on the choice of ligand and also correlates with coordination number for Pt-ligand and Pt-Cl-. Of the three ligands examined in our study, the one with the lowest Pt coordination number, 1,10-phenanthroline-5,6-dione (PDO), shows the lowest reaction temperature and highest reaction rate, likely due to those metal sites being more accessible to reactant adsorption. In situ XAS experiments show that the activity also correlates with good heterolytic dissociation of hydrogen, which is supported by OH/OD exchange experiments and is the rate-determining step of the hydrogenation reaction. In these in situ XAS experiments up to 190 °C, the supported Pt-ligand catalyst shows excellent stability against structural and chemical change. In addition to Pt, the PDO ligand coordinates with Ir on TiO2. These Ir SACs show slow activation by loss of Ir-Cl bonds, then excellent stability in the hydrogenation of ethylene by remaining a stable Ir-PDO structure. These results provide the chance to engineer ligand-coordinated supported catalysts at the single-atom catalyst (SAC) level by the choice of ligand and enable new applications at relatively high temperature.

Ligand-coordinated single Pt atoms on TiO2 and their dynamic response during hydrogenation catalysis

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.