Mechanism of TiO2 stabilization and promotion of the synergistic zero-valent Fe‒Cu photocatalysis-persulfate degradation of phenol

Fe-Cu bimetal materials exhibit high catalytic degradation activity with more active sites, faster charge transfer efficiency and synergistic effects on redox pairs. However, it faces the problems of easy compounding and instability. Therefore, we designed and synthesized Fe-Cu/TiO₂ composite catalysts and constructed a synergistic photocatalytic-persulfate degradation system. The phenol (50 ppm) degradation efficiency of 70 % Fe-Cu/TiO₂ was 97.3 % after 30 min of reaction, which was 1.49 and 16.51 times greater than those of Fe-Cu and TiO₂, respectively. This was attributed to the fact that mixing TiO₂ and Fe-Cu not only effectively promoted Fe-Cu dispersion but also improved the number of active sites and catalytic degradation activity. Moreover, the photogenerated electrons generated by TiO₂ could promote the valence transition between Fe-Cu, slowly releasing Fe²⁺ and Cu⁰ to realize the continuous activation of PDS and enhance the degradation activity. Quenching experiments and EPR results showed that the catalytic degradation process was dominated by the nonradical ¹O₂, with SO₄·^-, ·OH and ·O₂^- radicals interacting synergistically. Based on the characterization and experimental results, a synergistic degradation mechanism of Fe-Cu/TiO₂ was proposed, which provides a new approach for pollutant degradation.