Tubular ionizers are dielectric barrier discharge devices widely employed for indoor air purification. Nonetheless, their practical application is limited by low efficiency and high concentrations of harmful by-products, such as ozone. To address these challenges, we have developed a new approach to integrate tubular ionizers with catalysts by uniformly spraying MnO2 catalysts onto the tubular medium. This synergistic coupling of plasma and catalysis significantly enhances the catalytic performance, leading to near twofold increase in the conversion of HCHO, while reducing ozone concentrations to two-thirds of those in the plasma-only system. We have also developed a fluorescence probe to detect the presence of free radicals such as HO• and O2−•. Our results demonstrate that the catalyst loading generates more hydroxyl and superoxide radicals, leading to superior catalytic performance.