Recently, direct formic acid fuel cell (DFAFC) has attracted much attention due to the high theoretical open circuit voltage (1.48 V) and enhanced proton transport in the electrocatalyst layer. Although formic acid is considered as one of the best alternatives to methanol in fuel cells, there are several obstacles in preventing the commercialization of DFAFC. One of the main challenges of DFAFC is that the anode platinum (Pt) tends to be easily poisoned by intermediates formed during the incomplete oxidation process of the formic acid. As a potential alternative to Pt electrocatalyst, Pd with lower cost is believed to promote the formic acid oxidation (FAQ) through the direct pathway with less COads. Nevertheless, deactivation of Pd electrocatalyst does occur. Therefore, various Pd-based alloys have been synthesized to further enhance the electrocatalytic activity and stability. As the cost is about 35% lower than Pt, Ir is also reported as a superior secondary component to enhance the catalytic properties of Pd. In this study, multi-wall carbon nanotubes (MWCNTs) supported Pd100-xIrx alloy nanoparticles with different metal ratios were prepared, and applied as the electrocatalyst for the FAO process. As presented in the TEM image, nanoparticles are well dispersed on the surface of MWCNTs. The HRTEM image of a single nanoparticle shows the crystalline plane distances are 0.225 nm and 0.195 nm, which are larger than the standard d value of Pd (111) and (200) planes respectively. The XRD results indicated that Ir atoms might be incorporated into the surface lattice to substitute Pd atoms and formed the Pd100-xIrx alloy. The effects of alloy composition to the catalytic activity for the FAQ process were evaluated, and Pd79Ir21/MWCNT exhibited enhanced electrocatalytic activity when compared with Pd/MWCNTs. The stability analysis results further confirm the superior electrocatalystic activity and stability of Pd79Ir21/MWCNT.

Multiwalled carbon nanotubes supported palladium-Iridium alloy nanoparticles with enhanced electrocatalytic activity for the formic acid oxidation

249th National Meeting (2015)

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