Abstract
The electro‐oxidation of formaldehyde has been investigated at thermally prepared noble metal oxides, especially
, in aqueous solution. Studies were carried out on thin layers of oxide supported on Ta or Ti, and on thin, Teflonbonded oxide layers attached to a glassy carbon rotating disk electrode. The catalytic activity of 
for 
oxidation was considerably greater than that of 
and 
. At 
, formaldehyde was observed to undergo oxidation to formate at potentials from ca. 0.75–1.25V vs. reference hydrogen electrode (RHE), and to carbonate at higher potentials. The results suggest that 
(and 
) oxidation is mediated by higher valent states of the oxide metal ions electrogenerated at the electrode surface. Values of 10−3 cm s−1 (geometric electrode area based) and 10−6 cm s−1 (real area based) were estimated for the heterogeneous rate constant for 
oxidation at 
. The activity for 
oxidation is correlated with the catalytic activity of the oxides for the oxygen gas evolution reaction.