Shape-dependence in seeded-growth of Pd-Cu solid solution from Pd nanostructure towards methanol oxidation electrocatalyst

Ultrathin Pd nanosheets (NSs) have great advantages in catalysis due to their large specific surface area and high percentage of under-coordinated atoms. However, the electrochemical performance still can be improved via composition-controllable growth of their solid solution. Herein, seeded alloying strategy was proposed to synthesize Pd-Cu solid solution from Pd NSs and Pd-Cu nanostructures with tunable molar ratios obtained by changing the amount of Cu precursor. As compared to the pristine Pd NSs, the Pd-Cu solid solution shows significantly enhanced methanol oxidation reaction (MOR) performance over those of Pd NSs and homemade Pd/C as the incorporation of Cu weakens the adsorption of CO intermediate on Pd in the MOR process. The choice of template is pivotal to the growth, as a shape-dependent behavior could be identified in the alloying of Cu with Pd nanosheets enclosed by {111} and {100} facets, Pd nanocubes enclosed by {100} facet, and Pd nano-tetrahedrons enclosed by {111} facet. The Pd-Cu solid solution with tunable composition can only be obtained from Pd NSs and the shape-dependent alloying process is mainly determined by the diffusion barrier and the minimum diffusion depth of the different facets.