Long‐Term Stability of Light‐Induced Ti³⁺ Defects in TiO₂ Nanotubes for Amplified Photoelectrochemical Water Splitting

Abstract

This study shows that the simple approach of keeping anodic TiO2 nanotubes at 70 °C in ethanol for 1 h results in improved photoelectrochemical water splitting activity due to initiation of crystallization in the material amplified by the light‐induced formation of a Ti3+−Vo states under UV 365 nm illumination. For the first time, the light‐induced Ti3+−Vo states are generated when oxygen is present in the reaction solution and are stable when in contact with air (oxygen) for a long time (two months). We confirmed here that the amorphous or nearly amorphous structure of titania supports the survival of Ti3+ species in contact with oxygen. It is also shown that the ethanol treatment substantially improves the morphology of the titania nanotube arrays, specifically, less surface cracking and surface purification from C‐ and F‐based contamination from the electrolyte used for anodizing.