The Role of Electrodeposited Pd Catalyst Loading on the Mechanisms of Formic Acid Electro-Oxidation

This work addresses the effects of Pd nanoparticle loading and dispersion on the mechanisms of formic acid (FA) electro-oxidation. For this purpose, different levels of Pd nanoparticle loading (0.10–0.98 mg cm−2) with similar size (∼10–13 nm) were electrodeposited on the carbon cloth via square wave pulse technique. The mechanisms of FA oxidation in 0.5 M HCOOH + 0.5 M H2SO4 solution were studied and identified using cyclic voltammetry (CV) together with Fourier transform infrared spectroscopy (FTIR). Based on the obtained results, it was found that the electrochemical active surface area and Tafel slopes are independent of Pd loading levels, but both the shape and peak potential of the voltammograms are significantly affected by the Pd loading levels. The results of CV and FTIR showed that the different levels of Pd loading changes the FA oxidation pathway, which is attributed to the fact that the higher Pd loading results in the closer distribution of Pd nanoparticles. It was suggested that, at high Pd loading, the Pd-HCOOads formation is not the only available pathway for FA oxidation process and the Pd-COads formation pathway also exists, which is oxidized to CO2 at more anodic potentials.