Nanoscale Chemical Imaging of a Single Catalyst Particle with Tip‐Enhanced Fluorescence Microscopy

Determining the active site in real‐life solid catalysts remains an intellectual challenge and is crucial for exploring the road towards their rational design. In recent years various micro‐spectroscopic methods have revealed valuable structure‐activity data at the level of a single catalyst particle, even under reaction conditions. Herein, we introduce Tip‐Enhanced FLuorescence (TEFL) microscopy as a novel and versatile characterization tool for catalysis research. This has been achieved using a Fluid Catalytic Cracking (FCC) catalyst as showcase material. Thin sectioning of industrially used FCC particles together with selective staining of Brønsted acidity has enabled high‐resolution TEFL mapping of different catalyst regions. Hyperspectral information gained via TEFL microscopy reveals a spatial distribution of Brønsted acidity within individual zeolite domains in different regions of the FCC catalyst particle. Comparison of TEFL measurements from different FCC particles showed significant intra‐ and inter‐particle heterogeneities both in zeolite domain size and chemical reactivity.