Magnesiothermal reduction and doping strategies in engineered TiO2 for pharmaceutical degradation and CO2 conversion

Pharmaceutical contaminants in water pose a significant ecological risk and require advanced treatment solutions. In this study, the strategy of oxygen-deficient TiO_2-x and doping is evaluated for its photocatalytic efficiency under visible light for pharmaceutical pollutant degradation, seawater purification and green fuel production. The oxygen vacancies reduced the band gap and improved visible light absorption and charge separation, allowing TiO_2-x to achieve almost complete degradation of aspirin within 6 h. Mechanistic studies (EPR, LC-MS) revealed •O₂⁻ and h⁺ as the dominant reactive species. The TiO_2-x (1:1) catalyst showed excellent stability and reusability. Modified catalysts (TiO₂-Cu, TiO₂-GO) were also evaluated, with TiO₂-Cu and TiO_2-x (1:1) showing superior removal of organic pollutants (>90%), natural organic matter (NOM) and divalent ions (Mg²⁺, Ca²⁺) in seawater. While efficient degradation reduced biotoxicity (95% EC50 reduction in the Microtox assay), incomplete mineralization in some systems resulted in toxic intermediates, highlighting the need for combined chemical and toxicity assessments. In addition, TiO_2-x (1:1) and TiO₂-GO showed increased activity in CO₂ reduction. This work highlights oxygen vacancy engineering as a promising strategy for visible-light-driven environmental photocatalysis.