A strontium doped p–n heterojunction TiO2/Sr–Co3O4 composite for enhanced photocatalytic degradation of MG dye under solar light irradiation

The application of well-tailored semiconducting hybrid composites in purifying contaminated surface water is a greatly sought-after field. TiO₂, a prominent photocatalyst with higher band energy, was hybridised with strontium-doped Co₃O₄ nanoparticles for the effective degradation of malachite green (MG) dye under solar light. A TiO₂/Sr–Co₃O₄ composite with excellent visible light absorption ability and narrow band gap energy (E_g = 2.0 eV) was synthesised by applying a simple co-precipitation method. The structural, morphological and optical properties of the synthesized catalyst were analysed through XRD, FE-SEM, EDS, HR-TEM, FTIR, Raman spectroscopy, UV-DRS and surface properties were investigated via BET analysis. The doping of strontium metal on Co₃O₄ (p-type) acted as an electron facilitator to TiO₂ (n-type) at the p–n hetero-junction of the TiO₂/Sr–Co₃O₄ composite, increasing its efficiency towards photo-degradation of MG dye compared to pure Co₃O₄, TiO₂, Sr–Co₃O₄, and Co₃O₄–TiO₂ under solar irradiation. A maximum degradation of 92% occurred at pH 10 with a dye concentration of 20 ppm and catalyst dose of 0.02 g L⁻¹ in 60 min under solar irradiation. The photocatalytic degradation of MG dye by TiO₂/Sr–Co₃O₄ followed pseudo first-order kinetics. TiO₂/Sr–Co₃O₄ exhibited good stability by maintaining 80% degradation of MG dye after five consecutive cycles.