Electrochemical behaviour of CuO-TiO₂ catalysts

Abstract

In order to provide further information on the properties of CuO−TiO₂ catalysts, we have investigated their electrochemical behaviour in 1 M LiClO₄-propylene carbonate electrolyte. It appears that TiO₂ is electrochemically reducible at 1.8 V at room temperature, with a faradaic yield of 0.3–0.4 F per mole of TiO₂ with formation of a TiO₂Li_x phase according to the reaction:

$$TiO_2 + xe + xLi^ + \leftrightharpoons TiO_2 Li_x $$

The electrochemical study suggests that TiO₂ enhances Cu(II) electroreduction in titania-supported copper catalysts. This electroreduction of Cu(II) occurs either at 2.2 V according to the path:

$$Cu(II) + 2e \xrightarrow{{TiO_{2 } support}} Cu(O), TiO_2 $$

or at 1.8 V through an internal electron transfer between TiO₂Li_x and Cu(II) according to the successive reactions:

$$\begin{gathered} TiO_2 + xe + xLi^ + \leftrightharpoons TiO_2 Li_x \hfill \\ Cu(II) \xrightarrow{{TiO_{2 } Li_x }} Cu(O), TiO_2 \hfill \\ \end{gathered} $$

This study shows that electrochemistry may be a novel way of determining and controlling the redox states of metal-supported catalysis.