Recently, platinum-group metal (PGM) single atom catalysts have demonstrated interesting low temperature catalytic properties, which cannot be achieved with the nanometer-size counterparts, such as CO oxidation at cryogenic temperature. However, isolated metal atoms are usually mobile and tend to aggregate into clusters or particles during synthesis or reaction. As such, understanding and improving SACs’ durability while retaining high activity remains a great challenge. Meanwhile, the studies on SAC have been limited to model reactions such as CO oxidation and water gas shift, with little success over total hydrocarbon oxidation at low temperature.

In this talk, I will highlight a new type of single-atom Pt catalysts anchored on a highly stable mesoporous rutile titania nanowire array forest grown in field-size honeycomb monolith. With over 80% PGM usage reduction compared to that of the commercial benchmark diesel oxidation catalysts, such a new type of single atom Pt catalysts has displayed remarkable oxidation activities for total hydrocarbons with 90% conversion at temperatures approaching ~160 ^oC, ~172 ^oC lower than the commercial benchmark DOCs under the simulated diesel exhaust condition. In situ synchrotron X-ray adsorption spectroscopy and density functional theory calculation results confirmed that the isolated single atom Pt species with valence states between 2+ and 4+ dominated during the operation condition, and occupied the surface Ti vacancy sites and were strongly anchored by 5 or 6 O ions. As a result of such a strong electrostatic interaction between Pt single atom species and TiO₂ surface, these single atom Pt catalysts demonstrated remarkable low temperature oxidation activities and sustained durability toward hydrothermal aging and sulfation. Our work establishes a new type of practically viable nanowire array supported single atom catalysts, demonstrates the single atom catalysts’ potential for a real-world catalytic applications at low temperature here, and thus brings the scientific advancement closer to eventual technological applications.

Pu-Xian Gao

Professor, University of Connecticut

Appearances