Cu doped ZnFe₂O₄ photocatalysts for enhanced hydrogen production and dye degradation in the visible region

Cu doped ZnFe₂O₄ was synthesized using the hydrothermal method for photocatalytic hydrogen production and methylene blue (MB) degradation in the visible light region. Variation of Cu:Zn ratios transformed the crystalline phase into Cu_x doped Zn_(1-x)Fe₂O₄, evidenced by the constriction and expansion of crystal lattices. The other phases, CuO, ZnO, and Fe₂O₃ were identified depending on the degree of Cu dopants, affecting the band gap energy, surface area, and photocatalytic activity. Cu_0.25Zn_0.75Fe₂O₄ indicates the high level of Cu dopant into ZnFe₂O₄ lattices, exhibiting high suppression of charge recombination and transition to a more negative valence band positioned near the hydrogen evolution potential, producing 467.8 µmol/g hydrogen. MB degradation at 97.06 % with a rate constant of 61.4 × 10⁻³/min was achieved on Cu_0.75Zn_0.25Fe₂O₄.