RESUMO
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-MnO[x]] electrodeposited onto glassy carbon [GC] electrodes. Cyclic voltammetric [CV] measurements showed that unmodified GC and nano-MnO[x]/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-MnO[x] and nano-Pt results in superb enhancement of the direct oxidation pathway. Nano-MnO[x] is shown to facilitate the oxidation of CO [to CO[2]] 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-MnO[x]/nano-Pt/GC electrode [with Pt firstly deposited] compared to its mirror image electrode [i.e., with MnO[x]. firstly deposited, nano-Pt/nano-MnO[x]/GC] reveals that the order of the electrocldeposition is an essential parameter