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High spatial resolution mapping of catalytic reactions on single nanoparticles

Periodic Reporting for period 1 - MapCat (High spatial resolution mapping of catalytic reactions on single nanoparticles)

Reporting period: 2019-01-01 to 2020-06-30

The development of improved heterogeneous catalysts with enhanced reactivity and products selectivity will reduce the energetic cost and waste production of numerous chemical processes. Such progress in optimization of catalytic materials (and hence of chemical processes) relies heavily on gaining molecular level insight into the complex dynamics of catalytic reactions, which is the aim of this project.

Molecular level understanding of catalytic processes provides crucial knowledge about reaction mechanisms which is essential for the development of highly-efficient and selective catalysts. However, heterogeneities in the size, structure and composition of solid catalytic particles makes it difficult to directly monitor and identify the influence of various physiochemical parameters on the catalytic reactivity and selectivity. Thus, non-disruptive, detailed chemical information at the nanoscale is required for understanding how surface properties direct the reactivity of catalytic particles.

The overall goal of this project is to identify, on a single particle basis and under reaction conditions, the ways by which the size, structure, composition and metal-support interactions direct the reactivity of metallic nanoparticles in hydrogenation, oxidation and functionalization reactions. The knowledge gained by achieving these goals will provide guidelines for preparation of optimized catalysts.

In order to map the reactivity on single nanoparticles we employ high spatial resolution Infrared nanospectroscopy measurements, while using chemically active N-heterocyclic carbene molecules as indicators for surface-induced reactivity. With this setup we aim to identify the influence of various surface properties on the reactivity and selectivity of catalytic nanoparticles.
The main achievements during the first period of the project are:
1. Installation of AFM-IR setup
2. Setting in-situ capabilities in the AFM-IR setup that will allow measurements under variable temperature and gas environment (reducing/oxidizing conditions).
3. Developing a wide array of probe molecules and identifying their surface properties, such as their orientation, reactivity and stability (Fig. 1). These probe molecules will be utilized as local probes for surface-induced reactivity in the next phase of the project.
4. Probing site-dependent selectivity in oxidation reaction on single Pt particles.
The main progress that was achieved so far and is beyond the state of the art are:
1. Technical development of a unique spectroscopic setup that enables high spatial resolution IR measurements (~20 nm) under reaction conditions.
2. Probing the influence of dissimilar surface sites on the reactivity of Pt particles and identifying the connection between local surface properties and catalytic selectivity.

The spectroscopic and chemical capabilities that were developed in the initial stages of this project will allow us to achieve the following results until end of the project:
1. Identifying the influence of structure, composition and metal-support interactions on the catalytic reactivity of metallic nanoparticles (Fig. 2).
2. Probing the influence of neighboring particles on the reactivity and selectivity and the ways by which inter-particle communication can be utilized for tuning the reactivity and selectivity.