Size and Shape Effects on Nanoparticle-Catalyzed Reactions Enabled by High-Throughput Variable-Temperature Desorption Electrospray Ionization Mass Spectrometry

Nanoparticles exhibit unique catalytic properties that are highly dependent on their size and shape, influencing reaction rates, selectivity, and efficiency. Identifying the structural effects that achieve a high catalytic performance is critical to a wide range of applications, from energy conversion to environmental remediation. High-throughput screening (HTS) methods, particularly desorption electrospray ionization mass spectrometry (DESI-MS), offer a powerful approach for rapidly assessing the catalytic performance of nanoparticles with varying sizes and shapes. DESI-MS enables the direct analysis of reaction products without sample preparation, making it ideal for screening homogeneous catalytic reactions. However, applying this technique to heterogeneous catalysts remains challenging, and the lack of temperature control limits its ability to reflect realistic reaction conditions. In this article, we present the development of high-throughput variable-temperature DESI-MS (HT-vT-DESI-MS), a novel approach that combines DESI-MS with thin-film reaction acceleration and precise temperature control. This advancement allows the study of size and shape effects on nanoparticle-catalyzed reactions under varied conditions, offering a rapid understanding of structural parameters influencing catalytic performance. Our results show that varying the size of cubic Pd nanoparticles from 10 to 20 nm significantly impacts catalytic activity in Suzuki cross-coupling and indole arylation reactions, with distinct changes in both the effective surface area and Pd concentration. For both reactions, the reactivity trend normalized to the effective surface area was 10 nm cubic > 15 nm cubic > 20 nm cubic and normalized to the NP number was 20 nm cubic > 15 nm cubic > 10 nm cubic. Additionally, altering the nanoparticle shape from cubic to octahedral results in a marked decrease in product conversion, highlighting the critical role that nanoparticle morphology plays in determining catalytic efficiency. This research provides a HTS method for nanoparticle catalysts that can accelerate identification of design principles for their use in various catalytic applications.