Potentiodynamic estimation of key parametric criterions and interrelating reversible spillover effects for electrochemical promotion Original Research Article

Electrocatalytic peaks from potentiodynamic spectra for relevant electrode reactions have been employed to assess decisive and most important diagnostic criterions and parameters in the electrochemical promotion of heterogeneous catalysts (EPOC) and electrocatalysts. More specifically, the anodic oxidation of formaldehyde by the spillover supplied primary oxide of Pt (Pt-OH), both of them proceeding simultaneously as the fast reversible electrode processes of rather high faradaic yields, was investigated to estimate the relevance of catalytic peaks in cyclic voltammetry for the electrochemical promotion. In the same sense, catalytic potentiodynamic peaks have been used to prove and assess the entire spillover (or effusion) effect both of H-adatoms and the primary oxide itself, too, otherwise decisive for some significant electrochemical oxidation processes, such as CO tolerance and kinetics in the cathodic oxygen reduction (ORR), including electrocatalytic features of the latter, as the one of most important electrode reactions in aqueous media. The UPD and OPD spillover double layer charging and discharging properties of the primary oxide (M-OH), interrelated with the interactive self-catalytic effect of dipole-oriented water molecules, has also been pointed out. There has also been inferred that altervalent hypo-d-oxides impose spontaneous dissociative adsorption of water molecules and pronounced membrane spillover transferring properties instantaneously resulting with corresponding bronze type (Pt/HxWO3) under cathodic, and/or its hydrated state (Pt/W(OH)6), responsible for Pt-OH effusion under anodic polarization, this way establishing reversibly revertible alterpolar features (Pt/H0.35WO3 ⇔ Pt/W(OH)6) and substantially advanced electrocatalytic properties of these composite interactive electrocatalysts. Such nanostructured type electrocatalysts, even of mixed hypo-d-oxide structure (Pt/H0.35WO3/TiO2/C, Pt/HxNbO3/TiO2/C), have for the first time been synthesized by the sol–gel methods and shown rather high stability, distinctly pronounced electron conductivity and non-exchanged initial pure mono-bronze spillover and catalytic properties.