Efficient direct formic acid fuel cell (DFAFC) anode of nano-sized palladium complex: High durability and activity origin

Abstract

The low stability of Pd-based catalysts extremely obstructs their applied application in the direct formic acid fuel cells (DFAFCs). Herein, a novel nano-sized palladium-complex (nano-Pdcomplex) with outstanding performance (activity and durability) for DFAFCs anodic reaction (Formic acid oxidation; FAO) compared to the commercial Pd-based catalysts is introduced. Morphologically, nano-sized Pd-complex shows an intersected nano-rod like structure with an average particle size ca. 17nm. Electrochemically, nano-Pdcomplex modified GC electrode (Nano-Pdcomplex/GC) has 12 times higher electrocatalytic activity, 8.0 times higher electrochemical active surface area, 3.0 times higher catalyst utilization, and ca., 16 times higher stability after 5.0h than that of traditional Pd nanoparticles modified GC electrode (PdNPs/GC) with the same Pd loading. This significant enhancement in both activity and stability is attributed to nano-Pdcomplex bulky structure hindering the agglomeration of the Pd active sites and inhibiting the adsorption of poisoning CO-like intermediate species. DFT studies shows that nano-Pdcomplex has two different geometries: (a) cis-structure which has a square planar geometry and it is inactive for FAO, and (b) trans-structure with a tetrahedral geometry and it is highly active for FAO. This study introduces a new promising category of Pd-based catalyst with high activity, catalyst utilization and durability for DFAFCs applications.