Engineering the morphology of palladium nanostructures to tune their electrocatalytic activity in formic acid oxidation reactions

Abstract

Pd nanomaterials can be cheaper alternative catalysts for the electrocatalytic formic acid oxidation reaction (FAOR) in fuel cells. The size and shape of the nanoparticles and crystal engineering can play a crucial role in enhancing the catalytic activities of Pd nanostructures. A systematic study on the effect of varying the morphology of Pd nanostructures on their catalytic activities for FAOR is reported here. Palladium nanoparticles (Pd_0D), nanowires (Pd_1D) and nanosheets (Pd_2D) could be synthesized by using swollen liquid crystals as ‘soft’ templates. Swollen liquid crystals are lyotropic liquid crystals that are formed from a quaternary mixture of a surfactant, cosurfactant, brine and Pd salt dissolved in oil. Pd_1D nanostructures exhibited 2.7 and 19 fold higher current density than Pd_0D and Pd_2D nanostructures in the FAOR. The Pd_1D nanostructure possess higher electrochemically active surface area (ECSA), better catalytic activity, stability, and lower impedance to charge transfer when compared to the Pd_0D and Pd_2D nanostructures. The presence of relatively higher amounts of crystal defects and enriched (100) crystal facets in the Pd_1D nanostructure were found to be the reasons for their enhanced catalytic activities.