Various Morphology of WO₃ Modified Activated Carbon Supported Pd Catalysts with Enhanced Formic Acid Electrooxidation.

Abstract

Activated carbon support Pd nanoparticles (NPs) modified by various WO₃-shaped catalysts were prepared and applied as an efficient anode catalyst for direct formic acid fuel cells. Three forms of WO₃ (nanosheets, nanoparticles, nanobars) modified activated carbon hybrids were first prepared via different syntheses, and then used as supports to synthesize three types of Pd-WO₃/C catalysts by a NaBH4 reduction method. The morphology, structure, and electrochemical performances of the as-prepared Pd-WO₃/C catalysts were characterized and analyzed. We can see that the noble metal particles loaded with activated carbon modified by WO₃ exhibit small particle size and uniform dispersion from the transmission electron microscope image. The synthesized composite catalysts was used for the formic acid electrooxidation and showed excellent catalytic performance. The oxidation peak current density of the Pd/WO₃-Nanosheets/C (40.04 mA·cm-2 was the highest, approximately 1.2 times that of Pd/C (33.00 mA·cm-2. Additionally, the long-term stability (i-t) test results show that the Pd/WO₃-Nanosheets/C catalyst exhibits superior stability during formic acid electrooxidation. The reason for the increase in performance can be attributed to the following: the large specific surface area of WO₃ decreases the adsorption strength of intermediates such as COad on Pd and prevents the accumulation of poisonous intermediates, thereby promoting the oxidation reaction of formic acid in the direct pathway; the catalyst-support interaction between precious metal Pd and WO₃, substantially improving the catalytic performance of Pd-WO₃/C catalysts.