Zirconia Modified Pd Electrocatalysts for DFAFCs

Abstract

In order to enhance the Pd based anodic catalysts for direct formic acid fuel cells (DFAFCs), the research work includes increasing catalyst activity and preventing CO poison. In this study, various zirconium oxides-modified multi-walled carbon nanotubes (MWCNTs) were prepared as the supports of Pd catalysts for DFAFCs by adjusting the preparation parameters: metal adding, sintering temperature and atmospheres. The prepared pure zirconia has both monoclinic and tetragonal phases. The addition of MWCNTs depresses the growth of monoclinic phase. A small amount of Pd adding allows both monoclinic and tetragonal zirconia structures to appear again. Pd nanoparticles of 20 wt% synthesized on MWCNTs and tetragonal ZrO2/MWCNTs have similar particle size, while Pd/[Pd:ZrO2/AO-MWCNTs-300Air-900Ar] have more nanoparticles aggregation. The electrochemical surface area can be improved by adding zirconia which implies those zirconia modified Pd catalysts better electrocatalytic performance. By analyzing the maximum current density and the corresponding potential, Pd/AO-MWCNTs are inferred to undergo the formic acid direct oxidation initially. The Pd catalysts modified by tetragonal ZrO2 have higher current density. Those having both tetragonal and monoclinic ZrO2 modified Pd catalysts have lower potential of formic acid oxidation. All the Pd based catalysts with zirconia modification possess better CO resist ability and electrocatalytic activity. Pd/[ZrO2/AO-MWCNTs-300Air-900Ar] and Pd/[Pd:ZrO2/AO-MWCNTs-300Air-900Ar] which catalyze formic acid in direct oxidation path are the two best catalysts.