Skip to main content

ALS

Home / News / Science Briefs / COSMIC Probes Evolution of Single-Atom Platinum Catalyst

COSMIC Probes Evolution of Single-Atom Platinum Catalyst

Catalysts based on “noble metals” (gold, silver, platinum) are essential to critical chemical reactions that support daily life. For example, platinum catalyzes the CO oxidation reaction, central to the catalytic converters that control automobile emissions. However, because noble metals are expensive and earth-unabundant, there is strong economic incentive find ways to do more with less.

One approach is to maximize the available reaction sites by distributing single atoms (SAs) of platinum evenly over the surface of a support. In this work, researchers formulated a precise, atomic-level, interface-control strategy to synthesize a catalyst with platinum single atoms (Pt-SAs) densely and homogenously distributed over the surface of a CeOx–TiO2 oxide powder support. They hypothesized that strong electronic interactions between the Pt and Ce would stabilize the Pt-SAs at the Pt–CeOx–TiO2 interfaces.

At ALS Beamline 7.0.1.2 (COSMIC Imaging), the spatio-temporal evolution of the Ce oxidation state was probed using scanning transmission x-ray microscopy (STXM) under operando conditions—a first for this beamline. The results confirmed that the size of the catalytic Pt species and the locations of the reaction sites were dictated by the electronic state of the Ce ions. In addition, the researchers included density functional theory calculations and catalytic performance tests in this comprehensive study. The mass-normalized activity of the Pt-SA catalyst was found to be 15 times higher than that of conventional Pt–TiO2 catalysts.

The results demonstrate how both physical stability and high catalytic activity can be achieved in noble-metal SAs using interface control, and they should help accelerate the commercialization of less-expensive noble-metal-based catalysts with excellent long-term stability and catalytic consistency.

Silver spheres float at varying distances in a black space. About half are covered with tiny, paired yellow and blue spheres. The others are covered with medium-sized gold spheres. At upper right, a series of concentric rings—a Fresnel zone plate lens—is positioned as if to focus x-rays onto the spheres.
Artistic depiction of TiO2 nanoparticles (silver spheres). Hybrid CeOx–TiO2 nanoparticles are shown densely and evenly covered with Pt–Ce pairs (yellow and blue). Conventional TiO2 particles are shown more sparsely covered with larger Pt clusters (gold). The inclusion of a Fresnel zone plate (a “lens” for an x-ray microscope) highlights the importance of x-rays in investigating the atomic-scale morphology of the catalysts.

M. Yoo, Y.-S. Yu, H. Ha, S. Lee, J.-S. Choi, S. Oh, E. Kang, H. Choi, H. An, K.-S. Lee, J.Y. Park, R. Celestre, M.A. Marcus, K. Nowrouzi, D. Taube, D.A. Shapiro, W. Jung, C. Kim, and H.Y. Kim, “A tailored oxide interface creates dense Pt single-atom catalysts with high catalytic activity,” Energy Environ. Sci. 13, 1231 (2020), doi:10.1039/c9ee03492g.