Z-scheme photocatalytic dye degradation on AgBr/Zn(Co)Fe₂O₄ photocatalysts supported on nitrogen-doped graphene

In this work, we have synthesized AgBr-modified cobalt ferrite (CF) and zinc ferrite (ZF) combined with N-doped graphene (NG) via a modified hydrothermal process. Exploiting visible light, the photocatalytic performance of as-fabricated photocatalysts were used for successful photocatalytic degradation of malachite green (MG) and methyl orange (MO). The photodegradation of MG after 100 min followed the trend AgBr/CF/NG (98%) > AgBr/ZF/NG (95%) > CF (45%) > ZF (43%) > AgBr (41%) > NG (21%). For the degradation of MO, the abolition efficiency after 100 min followed the trend AgBr/CF/NG (99%) > AgBr/ZF/NG (96%) > CF (41%) > AgBr (40%) > ZF (38%) > > NG (23%). The rate constants of 0.034 and 0.032 min⁻¹ were attained for MG degradation using AgBr/CF/NG (R², 0.99) and AgBr/ZF/NG (R²: 0.98) photocatalyst, respectively, whereas AgBr/ZF/NG (R²: 0.98) and AgBr/CF/NG (R²: 0.97) had respective rate constants of 0.029 and 0.026 min⁻¹ for MO photodegradation. The intermediate formation during the process of photodegradation was studied by HPLC and GC-MS analysis. The adsorption experiments demonstrated that maximum adsorption of MG was at pH 4, whereas the maximum MG adsorption was at pH 8. Owning to recycle experiments, AgBr/ZF/NG and AgBr/CF/NG revealed 85% and 83% degradation efficiency, respectively, after ten consecutive cycles.