Palladium Particles Modified by Mixed-Frequency Square-Wave Potential Treatment to Enhance Electrocatalytic Performance for Formic Acid Oxidation

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.

Clean Electrochemical Synthesis of Pd–Pt Bimetallic Dendrites with High Electrocatalytic Performance for the Oxidation of Formic Acid

“…Subsequently, a slow decay of the current density was observed, which was associated with surface poisoning by intermediates [7]. The current density of the Pd-Pt bimetallic catalysts with a dendritic morphology for a period of 3000 s was 0.08 A mg −1 , which was higher than those of PdPts-10 Hz (0.04 A mg −1 ), PdPts-90 Hz (0.04 A mg −1 ), PdPts-1 H (0.02 A mg −1 ), and PdPts-2 H (0.03 A mg −1 ), even four times that of the commercial Pd/C catalyst reported in the literature (about 0.02 A mg −1 ) [36]. This indicated that the Pd-Pt bimetallic catalysts with a dendritic morphology possessed an outstanding catalytic activity and a high stability towards FAOR in an acid medium.…”

“…Two well-defined current peaks P1 and P2 appeared at about 0.44 V (vs. SCE) and 0.78 V (vs. SCE) (Figure 6a), corresponding to the direct oxidation of formic acid to CO2 and oxidation of adsorbed CO generated by dehydration of formic acid, respectively [7,14]. The Pd-Pt bimetallic catalysts with a dendritic morphology (PdPt-50 Hz (4 H)) exhibited the highest mass activity (P1, 0.77 A mg -1 ) among the obtained Pd-Pt bimetallic catalysts towards FAOR and was almost 2.5 times that of the commercial Pd/C catalyst (0.31 A mg -1 ) [36]. Furthermore, the Pd-Pt bimetallic catalysts with a dendritic morphology also displayed a higher mass activity compared with the reported Pd-based electrocatalysts towards FAOR (Table 1).…”

“…For example, Tian et al [33,34] synthesized monometallic Pt and Pd tetrahexahedral nanocrystals by the electrochemical technology, which showed a high electrocatalytic activity for the oxidation of formic acid and ethanol. The dendritic Pt and highly dispersed Pd particles also synthesized by a similar electrochemical method and displayed a high electrocatalytic activity [35,36]. However, there are few reports on the synthesis of morphology-controlled Pd-Pt bimetallic catalysts via a clean electrochemical approach.…”