A Local Probe Mass Spectrometer for Localized and Sensitive Product Detection in Environmental Electron Microscopy

TL;DR

This paper introduces a novel local probe mass spectrometer integrated with aberration-corrected environmental transmission electron microscopy, enabling spatially resolved detection of reaction products at atomic resolution.

Contribution

It develops a new setup combining ETEM and MS with a micro-capillary sampling method for localized, high-resolution chemical analysis of catalytic processes.

Findings

Validated controlled gas delivery to the MS in environmental SEM.

Used electron-transparent Co3O4 nanoplates for atomic-resolution imaging.

Established a micro-shuttle transfer strategy for precise catalyst placement.

Abstract

Aberration-corrected environmental transmission electron microscopy (ETEM) enables atomic-resolution imaging of dynamic catalytic processes. Correlating atomic-scale structural changes with reaction products detected by mass spectrometry offers a powerful route to uncover catalytic mechanisms. However, current approaches face fundamental limitations: closed-cell ETEM setups suffer from diffuse scattering by SiN windows, degrading spatial resolution and sensitivity, while open-cell configurations enable high-resolution imaging and maintain high sensitivity but suffer from significant dilution of reaction products during transport to the mass spectrometer (MS). To overcome these challenges, we develop a Local Probe Mass Spectrometer (LPMS) integrated with aberration-corrected ETEM. The setup combines a DENSsolution Stream holder with a MS. To preserve spatial resolution, both top and bottom SiN membranes of the MEMS chip are removed, while the gas environment is maintained via the ETEM chamber. Reaction products are sampled locally via a micro-capillary positioned near the catalyst and connected to a holder gas line that delivers the gas to the MS. Initial validation in environmental SEM confirmed controlled gas delivery to the MS. Co3O4 nanoplates serve as a model catalyst due to their inherent electron transparency, enabling atomic-resolution imaging without FIB lamella preparation and associated ion-beam damage. A novel micro-shuttle transfer strategy enables controlled placement of a defined number of nanoplates at the reaction site with precise crystallographic orientation. This establishes the foundation for quantitative structure reactivity correlation by enabling simultaneous, spatially resolved detection of reaction products and atomic-scale structural dynamics.