1D Pd-Based Nanomaterials as Efficient Electrocatalysts for Fuel Cells - Low-cost Nanomaterials: Toward Greener and More Efficient Energy Applications - page 325

Fig. 7 SEM and TEM (HRTEM) images of nanoporous copper (a, b) and nanotubular
mesoporous PdCu bimetallic nanostructure (c-f), respectively. Reprinted from Ref. [ 77 ] with
permission by the American Chemical Society
formed PdCu bimetallic nanocomposites display nanotubular mesoporous nano-
structures. The electrochemical polarization curves of the nanotubular mesoporous
PdCu (NM-PdCu) revealed that the half-wave potential of the NM-PdCu for ORR
was 0.840 V, which was 60 mV more positive than that of the commercial Pd/C
catalysts. Moreover, the NM-PdCu catalyst is also superior to the commercial Pt/C
(0.825 V) catalyst with more positive half-wave potential. The calculated specific
activity of NM-PdCu at 0.8 and 0.85 V is 1.5 and 1.4 times that of the Pt/C catalyst
at the respective potentials. From the Koutecky-Levich curves in rotating disk
voltammetry measurements, a nearly complete reduction of O 2 to H 2 O on the
NM-PdCu surface via an efficient four-electron reaction process was obtained.
More importantly, based on the experimental results, NM-PdCu catalyst showed
enhanced methanol tolerance as compared with the commercial Pt/C and Pd/C
catalysts. The enhanced ORR activity, stability, and methanol tolerance were
ascribed to the presence of sublayer Cu atoms, which provide an electronic mod-
ification for the topmost Pd layer by a surface strain effect or an alloying effect. This
effect could provide unique surface sites for the adsorption of O 2 molecules and be
beneficial for their subsequent electro-reduction. Furthermore, the unique three-
dimensional bicontinuous spongy structure and various hollow channels provide
good transport channels for medium molecules and electrons, which may greatly
facilitate the reaction kinetics of ORR on the catalytic surfaces.