  Chemisorption process and catalytic activity of CO to CO2 conversion on
PdXRu1-X (X : 0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1) extended as a benchmark for
further investigation of very complex nanoparticle (NP) structures have been
checked into thoroughly by using the synchrotron-based hard X-ray photoelectron
spectroscopy (HAXPES). Assessment and diagnostic of core levels and valence
bands data highlight valuable information regarding the surface interaction and
structure of PdRu bimetallic nanoparticles (BM-NPs). Core level shift observed
from the C 1s clearly emphasized that the Pd0.5Ru0.5 NPs which provide the
highest catalytic efficiency (CO oxidation) exhibits a preferential adsorption
of the CO molecule at the top site. Otherwise, our results also display that
remaining NPs exhibit two components assigned to the bridge and hollow CO
sites. Combination of Pd 3d5/2 and Ru 3p3/2 core levels results points out a
transition from alloy structures to core-shell configuration with increasing
the molar ratio of Ru. Valence-band maximum (VBM) demonstrates a position
dependent to the molar composition of Ru. Additionally, by digging into the
electronic structures (shape and width) of each NPs very deeply, we clearly
emphasise the valuable relationship between composition, atomic arrangement,
d-band and catalytic properties of bimeatllic PdRu. According to the HAXPES
results, the strong and clear evidence for the enhanced CO to CO2 conversion
ability of Pd0.5Ru0.5-NP may be assigned to the existence of a most favourable
spatial d-band extension and an optimum balance between the core-shell and
alloy structures. Electronic and chemical data and interpretations are
consistent with the PdRu catalytic performances. This present prospection gives
a new step towards a better knowledge on the catalytic surface interaction of
binary, ternary and multimetallic NPs with reactants.
