Improved Catalysis of Green-Synthesized Pd-Ag Alloy-Nanoparticles for Anodic Oxidation of Methanol in Alkali

Abstract

Monometallic Pd, Ag and bimetallic PdxAgy alloy nanoparticles were synthesized in a single pot using a green synthetic protocol in absence of any capping agent. X-ray, electron diffraction, microscopic and spectroscopic studies of synthesized material demonstrate the formation of nanoballs with radius of 10–20nm of face centred cubic metals and alloys. The electrochemical studies of as-synthesized materials loaded on carbon support reveal that the Pd4Ag nanoparticles exhibit the best and synergistic electro-catalytic activity in reference to oxidation of methanol in alkali. The most active Pd4Ag nanoparticles show higher peak current (201mAmg−1) in comparison to that (133mAmg−1) of Pd in cyclic voltammetric study. The electrode shows the highest exchange current density (1.95×10−2mAmg−1 of Pd) for methanol oxidation reaction (MOR) and higher catalytic activity for oxidation of possible intermediates like formaldehyde and sodium formate of MOR. Ex-situ infrared spectrometry and chromatographic studies of reaction products reveal that Ag accelerates the formation of formate rather than carbonate elucidating the plausible mechanism of the reaction. These findings have important implications for further fine-tuning of the Pd nano alloys toward highly active and selective catalysts for alcohol fuel cells.