| Popis: |
Our team at the U.S. Naval Research Laboratory is pursuing an opportunity unique within heterogeneous catalytic science: Correlating catalytic activity to our ability to integrate multiple transport and reactivity functions within practical, not model, architectures. We exploit sol–gel-derived aerogels as a hierarchical platform—structurally complex, but functionally simple—to address in detail whether controlling ionic transport to three-phase boundaries affects the catalytic activity of AuNP–modified oxide nanoarchitectures for model, CO-centered reactions and for the oxidation of water and alcohols. We can also address whether long ionic diffusion lengths (determined via impedance measurements) correlate with local ion mobility near the catalysis zone (monitored by NMR spectroscopy) and does either length scale affect catalytic activity (tracked by determining reaction turnover frequency)? Our synthetic processing protocols to control pore–solid architectures are established, ranging from a continuous 3D porous network with 1–100 nm pores (aerogel) to a continuous 3D porous network containing only 10–50 nm mesopores (ambigel) to a collapsed porous network with 10 nm pores (xerogel). The choice of architecture determines the through-connectedness of two critical transport networks: electrical wiring along the solid network and facile molecular flux through the pore network (approaching open-medium diffusion rates). This class of hierarchical nanoarchitectures provides a tunable platform with which to develop comprehensive mechanistic understanding that will allow us to design next-generation catalytic architectures with superior performance. |
