A catalyst coated electrode for electrochemical formaldehyde oxidation

Thermally prepared catalytic coatings on a titanium substrate were composed of a mixture of nanocrystals of metallic Pt and RuO 2 of rutile structure and used for electrooxidation of formaldehyde. The size of the RuO 2 nanocrystals increased, whereas those of Pt decreased with increasing the content of RuO 2 in the mixture. At more positive potentials, the maximum catalytic activities showed the coatings with lower content of RuO 2 . Mechanism of formaldehyde oxidation was derived to show two reaction pathways. In the first one, H 2 C(OH) 2 was directly oxidized to CO 2 , whereas CO ad was formed in the latter. CO ad is strongly adsorbed on Pt atoms, which causes blocking of these atoms and thus, preventing direct dehydrogenation of H 2 C(OH) 2 to CO 2 . The overall catalytic effect of the mixture of nanocrystals was caused by the bifunctional mechanism. Thus, the Ru atoms formed the oxy species at more negative potentials than Pt. These oxy species oxidized the CO ad intermediates, bound to adjacent Pt atoms and accordingly, discharged them for dehydrogenation of new molecules of H 2 C(OH) 2 . Graphic abstract