Impact of high-pressure columbite phase of titanium dioxide (TiO2) on catalytic photoconversion of plastic waste and simultaneous hydrogen (H2) production

Abstract

Photoreforming is a sustainable photocatalytic process that degrades plastic waste while simultaneously producing hydrogen (H2) from water. However, this process has received limited attention due to the scarcity of effective catalysts capable of both plastic degradation and H2 production, such as titanium dioxide (TiO2). In this study, an active catalyst is developed by stabilizing the high-pressure orthorhombic phase of TiO2, known as columbite, using a high-pressure torsion (HPT) method. This material effectively degrades polyethylene terephthalate (PET) plastic under light, converting it into valuable organic compounds such as formic acid, terephthalate, glycolic acid, and acetic acid. Additionally, it produces a significant amount of H2. The findings show that the high-pressure orthorhombic phase, especially in the presence of oxygen vacancies, enhances catalytic H2 production and microplastic degradation by increasing light absorption, reducing electron-hole recombination, and generating hydroxyl radicals. These results highlight the substantial potential of modified high-pressure TiO2 photocatalysts in simultaneously addressing the plastic waste crisis and the demand for H2 fuel.