Advances in TiO₂-based photocatalysts for environmental remediation: Structural engineering, mechanistic insights, and degradation pathways of organic and inorganic pollutants

TiO₂-based photocatalysis has become a promising strategy for the degradation of volatile organic compounds (VOCs) and inorganic gaseous pollutants. This review provides an analytical examination of how structural design, surface engineering, and electronic modulation influence the photocatalytic performance of TiO₂ materials. Emphasis is placed on the role of crystal facets, oxygen vacancies, heterojunction interfaces, and metal/non-metal dopants in regulating charge-transfer dynamics and suppressing electron–hole recombination. Mechanistic pathways for the oxidation of aldehydes, aromatics, trichloroethene, NOx, SOx, CO, ozone, and H₂S are systematically outlined, focusing on radical formation and kinetic behavior. Finally, the review highlights key design principles and performance-governing factors that can guide the development of high-efficiency TiO₂ photocatalysts for future environmental remediation systems.