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 18.104.22.168 (COSMIC Microscopy), 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.
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.