The massive production of the modern manufacturing imposes a strict control of the waste produced, in particular wastewaters. Oxalic acid is one the most renowned intermediate in wastewater treatment processes. However, it can be turned into a valuable chemical through its electro-reduction to glyoxylic and glycolic acids as a feedstock for many chemical industries. Among the catalyst employed in catalytic wastewater decontamination, TiO2 rises the highest attention because of its good stability to corrosion, earth abundancy, low cost, low toxicity, chemical, and thermal stability. In order to select the most-performing TiO2 nanostructure, the activity and stability toward oxalic acid electro-reduction has been analyzed by employing TiO2 nanotubes (TNT), nano-flames structures (TNF), and commercial nanopowders (TNP). Among them, TNT showed better electrocatalytic activity, followed closely by TNF, with a current density about three times higher than TNP, as well as better selectivity. The double layer capacitance analysis shows that TNT has a peculiar structure which guarantees a higher active surface. As a final result, the impedance spectroscopy showed that both TNT and TNF electrodes exhibit lower resistance and enhanced stability and durability with respect to TNP.
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