Abstract
Palladium catalysts have attracted widespread attention as advanced electrocatalysts for the formic acid oxidation (FAO) due to their excellent electrocatalytic activity and relatively high abundance. At present, electrodeposition methods have been widely developed to prepare small-sized and highly-dispersed Pd electrocatalysts. However, the customary use of surfactants would introduce heterogeneous impurities, which requires complicated removal processes. In this work, we reported a two-step electrochemical method that employed square-wave potential treatment (SWPT) to modify electrodeposited Pd particles without the use of capping agents. Under the SWPT with a mixed frequency, Pd particles show significantly reduced size and more dispersed distribution, exhibiting a high mass activity of 1.43 A mg−1 toward FAO, which is 4.6 times higher than the counterpart of commercial Pd/C. The increase in electrocatalytic activity of FAO is attributed to the highly developed surface of palladium particles uniformly distributed over the support surface.
Highlights
At a constant deposition current density of −0.15 mA cm−2 in 5 mM PdCl2 and 0.5 M H2 SO4, the Pd particles are featured with irregular polyhedron morphology and their sizes range from 200–300 nm (Pds–Des, Figure 1a)
The curve features a stable current plateau with a voltage of approximately 0.06 V (vs. mercury sulfate electrode (MSE)), which corresponds to the growth process [35,36]
Pd NPs were successfully fabricated on carbon paper substrate using a two step electrodeposition–square-wave potential treatment (SWPT) method without the use of capping agents
Summary
Palladium (Pd) electrocatalysts shows great significance in many applications including the fields of electrocatalytic oxidation of several organic molecules and reduction of oxygen, metal-air batteries, and fuel cells [1,2,3,4,5,6,7] due to the excellent electrocatalytic activity and relatively high abundance (compared to platinum (Pt)) [8,9]. In order to fully utilize Pd metal and improve its catalytic performance, great efforts have been devoted to reducing the particle size of Pd electrocatalysts to increase active exposed faces [10,11,12,13]. With decreasing particle size, the surface energy of electrocatalysts will increase, leading to severe aggregation of the small particles and reduction of total surface energy in the preparation process [14,15]
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