Fig. 2: Particle size and work function values of various Ru-based samples.

TEM images of Ru crystals in different size: a Ru-1.0, b Ru-2.3, c Ru-3.1. d–f Corresponding size distribution of various Ru samples. g HADDF-STEM images of Ru-1.0. h UPS spectra of Ru clusters. i Correlation between particle size and Ф values.