Electrochemically self-doped TiO2 nanotube photoanodes decorated with Pt nanoparticles: trade-off between photocatalytic activity and dark electrocatalysis for ethanol oxidation

TiO 2 nanotube electrodes are commonly used in photoelectrocatalytic applications; however, their poor conductivity limits their electrochemical potential. In this work, we have prepared self-doped TiO 2 nanotube electrodes by electrochemical anodization followed by electrochemical cathodic polarization. Electrochemically self-doped TiO 2 nanotube (SD-TNT) electrodes were prepared by cathodic polarization and subsequently decorated with Pt nanoparticles (3.3 ± 0.6 nm) via impregnation and electrochemical reduction. SD-TNT supports a complete Pt voltammetric profile and enables ethanol electro-oxidation in the dark. In contrast, Pt-decorated pristine nanotubes (Pt/TNT) exhibit only hydrogen adsorption/desorption features and no anodic currents in acidic media. Under simulated solar irradiation, pristine TNT exhibits the highest photocurrents and product formation. At the same time, both self-doping and Pt decoration decrease the photocurrent density, highlighting a trade-off between enhanced dark conductivity and increased recombination in highly defective TiO 2 . Nevertheless, Pt/SD-TNT electrodes combine dark electrocatalytic activity with photoresponse, operating in a dual mode that is relevant for devices under intermittent illumination. These results clarify the distinct roles of self-doping and Pt decoration on TiO 2 nanotube electrodes, highlighting a trade-off between maximizing photocurrent and enabling Pt-based electrocatalysis on a normally rectifying semiconductor support. • ~3 nm Pt nanoparticles deposited on TiO 2 nanotubes (TNT) by adsorption/reduction. • On undoped TiO 2 , Pt voltammetry is limited to the cathodic region in acid. • Self-doping activates TiO 2 nanotubes for dark Pt-catalyzed ethanol oxidation. • Pt and self-doping (SD) lower TiO 2 photocurrent, revealing a conductivity trade-off. • Pt/SD-TNT electrodes work in dual mode: dark and photoassisted ethanol oxidation.