Fig. 6a and b shows the STEM images of fresh and used 3J1 catalyst
while Fig. 6c and d presents the EDS profiles at certain locations
for the particles shown in the images. The particle size varies from
20 nm to particles, which are as small as 1–2 nanometers. In general,
the particles can be grouped into two size groups, large particles in
the range of 8–20 nm and a smaller size group ranging from few nm
to as large as 6 nm. Position 1 is representative of the small particles
found in fresh 3J1 catalyst while position 2 is for large particles. It
has been found that the large particles show the presence of both Ni
and Pd and essentially, no Rh. The same can be seen in the EDS profiles
in Fig. 6c and d. Ni was characterized by a peak at 80 and 750 eV.
Pd was identified by peaks at 275 and 2120 eV while Rh was found
at 265 and 2010 eV. Ni was present as large particles in the range of
8–20 nm with or without the presence of Pd. Small particles essentially
contain Rh while traces of Ni and Pd can be observed in some
cases. Elemental mapping of used 3J1 catalyst was also performed
as shown in Fig. 6e (Ni mapping) and Fig. 6f (sulfur mapping), and
confirms that the large particles were largely made up of Ni.