Realtime observation of a tungsten-promoted size regulation mechanism in a rhodium catalyst at atomic resolution

TL;DR

This study employs low dose electron microscopy to observe in real time how tungsten influences the size regulation of rhodium nanoparticles on alumina, revealing a tungsten-promoted ripening mechanism at atomic resolution.

Contribution

It demonstrates the first real-time atomic-resolution observation of a tungsten-promoted size regulation mechanism in rhodium catalysts, using low dose electron microscopy.

Findings

W atoms strongly bind to support oxygen, inducing strain as clusters grow.

Real-time imaging captures size regulation dynamics.

W promotes a ripening process affecting nanoparticle size.

Abstract

The static and genuine structure of small rhodium and rhodium/tungsten nanoparticles on an alumina support can be imaged with atomic resolution even if single digit atom clusters are investigated. Low dose rate electron microscopy is key to the achievement and can generally be applied to investigate any similar material. In such conditions it becomes feasible to identify the chemical composition of nanocrystals from quantitative contrast analyses alone by counting atoms. The ability to fully characterize an unaltered, initial state of the objects allows targeting structural excitations or conformational changes induced by the electron beam itself. For the specific case of catalytic Rh:W particles we stimulate a tungsten-promoted size regulation mechanism in real time that is driven by Oswald ripening and can be understood by a strong binding of tungsten atoms to the oxygen atoms of the support, which builds up strain as the cluster sizes increase.