Ultra-thin layer of oxygen vacant amorphous titania for enhanced photocatalysis

Abstract

Titanium dioxide (TiO₂) is a widely utilized photocatalyst owing to its chemical stability and UV-responsive activity; however, its wide bandgap and rapid charge carrier recombination limit its overall performance. Defect engineering has emerged as a promising strategy to overcome these limitations and enhance photocatalytic efficiency. In this study, we demonstrate that TiO₂ thin films fabricated under controlled plasma conditions via sputtering develop an approximately 4-nm-thick amorphous surface layer, which markedly enhances photocatalytic activity-achieving a 13-fold improvement compared to conventional anatase TiO₂. Comprehensive characterization using photoluminescence (PL) spectroscopy, transmission electron microscopy–electron energy loss spectroscopy (TEM–EELS), and first principles calculations confirms the presence of four-coordinated Ti species and oxygen vacancies within the amorphous layer. These defect states could promote charge trapping and molecular adsorption, thereby contributing to the enhanced photocatalytic performance. These findings offer new insights into the role of surface amorphization and defect engineering in photocatalysis, providing a foundation for the rational design of high performance and durable photocatalytic materials.