A quantitative electron tomography study of ruthenium particles on the interior and exterior surfaces of carbon nanotubes

The efficiency of filling carbon nanotubes (CNTs) by ultrasound-assisted wet impregnation is quantified by electron tomography (ET). For image analysis, a method that combines edge detection with single-value thresholding is proposed and validated. A high proportion (80wt %) of the ruthenium was deposited inside the tube at an average particle size of 2-4nm. Particles located on the outer surface of the CNT had a size of 1-3nm. The local ruthenium loading measured by ET (3.2wt %) closely matched the value from elemental analysis (3.5wt %). In addition, a few 1nm-sized ruthenium particles were detected inside the carbon wall, which contained pores/cracks. Direct imaging and quantification is a powerful tool to understand and possibly model the unique properties of CNT-based catalysts. Tomo arigato! The efficiency of filling carbon nanotubes by ultrasound-assisted wet impregnation is quantified by electron tomography. The method allows for automated and operator-independent quantification of nanostructured catalysts, contributing to a more rational design of this important class of materials in the future.