Highly efficient ZnCo2O4 nanospheres and ZnCo2O4/GO nanocomposites as visible light photocatalysts for degradation of organic pollutants

The increasing prevalence of environmental pollution has led to the development of photocatalysts as a viable approach for degrading synthetic and organic pollutants, such as dyes, in wastewater treatment. By using a controllable Pechini sol–gel technique, a visible light-responsive ZnCo₂O₄ nanophotocatalyst was fabricated for the degradation of methyl red and thymol blue as organic pollutants. A range of factors, such as the nature of cross-linking and capping agents, were implemented to assess their impact on the purity and particle size of ZnCo₂O₄. To the best of our knowledge, there is no existing research on ZnCo₂O₄ nanoparticles synthesized via the Pechini sol–gel method using different capping and cross-linking agents, particularly in terms of their ability to degrade dyes under visible light. Following this, graphene oxide (GO) was integrated onto ZnCo₂O₄ nanospheres to create a promising photocatalyst for the pollutant degradation under visible light exposure. The BET analysis indicates that the samples possess an average pore size within the mesopores range, which is optimal for photocatalytic activity. The ZnCo₂O₄/GO nanocomposite exhibited a band gap of approximately 2.37 eV that enhances the separation of charge carriers, reducing recombination rates and improving the photocatalytic efficiency. A high photodegradation efficiency of 94.3% was achieved for pollutant after exposure to visible light for a duration of 120 min, using the integration of GO (25% wt) with ZnCo₂O₄, which was higher than that of ZnCo₂O₄/GO-10% (78.7%), ZnCo₂O₄/GO-50% (81.6%), and pure ZnCo₂O₄ (91.4%). In addition, the presence of benzoic acid as a hydroxyl scavenger remarkably impacts the photocatalytic activity. This highlights the vital importance of OH• radicals in this process.