ABSTRACT This study aims to investigate a multi-component synergistic strategy for methylene blue (MB) degradation by coupling dielectric barrier discharge (DBD) plasma oxidation, black titanium dioxide ( TiO2)-assisted photocatalysis, and chloride ion (Cl−)-mediated oxidation. A gas–liquid needle–plate discharge configuration was employed with MB solution as a simulated wastewater model. The TiO2 and Cl− were introduced for synergistic treatment.