Enhanced Oxalic Acid Electroreduction Selectivity toward Glyoxylic Acid on Ti 3+ ‐Self‐Doped TiO 2 Nanotube Arrays

Abstract Electroreduction of oxalic acid (OX) to glyoxylic acid (GO) is an extremely important and promising application in organic electrosynthesis. Pb cathodes, which exhibits good selectivity, need to be replace due to the severe deactivation and harmful to the environment. Herein, self‐doped titanium dioxide nanotube arrays (H‐TiO 2 NTs‐2) are synthesized as an alternative cathode for OX electroreduction to GO. Benefiting from two‐step anodization, the synthesized nanotube arrays are highly ordered with oriented openings. The ordered structure promotes the mass transfer of both OX and GO to ensure efficiently providing OX reactants for the diffusion‐controlled OX electroreduction and removal of GO products from the electrode to prevent the over‐reduction to glycolic acid. Additionally, the electroreduction treatment introduces more Ti 3+ active sites and modulates the conduction band position of H‐TiO 2 NTs‐2, thereby enhancing the reduction driving force. Owing to the unique structural advantages, the Faraday efficiency of generating GO from OX reaches up to 81.3 % in an oxalic acid saturated electrolyte at 20 °C with a current density of 1500 A m −2 . This designed H‐TiO 2 NTs‐2 holds broad application prospects in OX electroreduction.