Platinum nanoparticles–manganese oxide nanorods as novel binary catalysts for formic acid oxidation

The current study proposes a novel binary catalyst system (composed of metal/metal oxide nanoparticles) as a promising electrocatalyst in formic acid oxidation. The electro-catalytic oxidation of formic acid is carried out with binary catalysts of Pt nanoparticles (nano-Pt) and manganese oxide nanorods (nano-MnOx) electrodeposited onto glassy carbon (GC) electrodes. Cyclic voltammetric (CV) measurements showed that unmodified GC and nano-MnOx/GC electrodes have no catalytic activity. While two oxidation peaks were observed at nano-Pt/GC electrode at ca. 0.2 and 0.55 V (corresponding to the direct oxidation of formic acid and the oxidation of the poisoning CO intermediate, respectively). The combined use of nano-MnOx and nano-Pt results in superb enhancement of the direct oxidation pathway. Nano-MnOx is shown to facilitate the oxidation of CO (to CO2) by providing oxygen at low over-potential. This leads to retrieval of Pt active sites necessary for the direct oxidation of formic acid. The higher catalytic activity of nano-MnOx/nano-Pt/GC electrode (with Pt firstly deposited) compared to its mirror image electrode (i.e., with MnOx firstly deposited, nano-Pt/nano-MnOx/GC) reveals that the order of the electrodeposition is an essential parameter.