Microdevices for High-Throughput Screening of Single Catalyst Particles

Heterogeneous catalysis is a dynamic field with a continuous focus on improving and developing more efficient, robust, and sustainable catalysts. Solid catalysts can exhibit different sizes, ranging from micrometers to centimeters, and various shapes. They are often porous particles with structural features that cover length scales from nanometers to centimeters, as they include sub-nanometer active catalytic sites, nanometer-scale metal clusters or nanoparticles, as well as multiscale pore networks. This range of structural features highlights the complexity of solid catalysts, with each component and hierarchical arrangement playing a significant role in their catalytic functions, namely activity, accessibility, and stability. Therefore, understanding and characterizing these materials is crucial for elucidating structure-activity relationships and developing catalysts with improved performance.

Traditionally characterization of catalyst particles is done in bulk, providing individual features of catalysts, such as concentration of active sites or accessibility, as an ensemble average over millions or billions of catalyst particles. Using that information for interpreting performance as well as enhancing the design of the catalyst requires the underlying assumption of uniformity in the properties across the individual particles in a catalyst batch. This assumption, however, may not always hold true given the variability that can exist at multiple scales (intra- and inter-particle heterogeneity).

In this context, microfluidic devices have emerged as powerful tools for accelerating catalyst development and characterization at the single-particle level. They allow for isolating and examining individual particles under controlled experimental conditions and hold a unique advantage in their capability for high-throughput analysis.

This thesis presents microdevices that enable the characterization of individual catalytic particles in terms of accessibility and activity. We explored high-throughput strategies based on the use of multiplexed devices with parallel chambers containing different particles, or the analysis of spatially resolved particles with a continuous flow system. The high-throughput screening approach allows for rapid testing of multiple particles or conditions while also resolving particle heterogeneities.