Green synthesis of MnVS and Co@MnVS nanoparticles: Applications in photocatalysis and hydrogen production via methanolysis

In this study, MnVS and Co@MnVS nanoparticles were synthesized using an environmentally friendly green synthesis method by employing flavonoid compounds from almond green husk extract as a reducing agent. The synthesized nanoparticles were characterized by EDX, XRD, SEM, and TEM analyses to determine their elemental composition, crystal structure, and morphological properties. XRD analysis revealed that the crystallite sizes of MnVS and Co@MnVS nanoparticles ranged from 3 to 15 nm. MnVS and Co@MnVS nanoparticles were used as catalysts in the methanolysis of NaBH₄ and the photocatalytic reduction of methylene blue with NaBH₄. In the methanolysis of NaBH₄, the effects of parameters such as NaBH₄ concentration, catalyst amount, and temperature on the reaction were investigated. In the photocatalytic reduction of methylene blue with NaBH₄, the effects of methylene blue and NaBH₄ concentration were investigated. The initial hydrogen production rates measured at 5 % NaBH₄ concentration for MnVS nanoparticles and Co@MnVS nanoparticles were determined as 10.833 ml/g.min and 11.777 ml/g.min, respectively. The kinetics of NaBH₄ methanolysis were evaluated using first-order kinetic model, and the activation energies for MnVS and Co@MnVS nanoparticles were determined to be 28.10 kJ/mol and 21.99 kJ/mol, respectively. As a result of the photocatalytic reduction of methylene blue with NaBH₄, the kinetic constants (k) for MnVS and Co@MnVS nanoparticles were determined to be 1.2273 min⁻¹ and 0.6868 min⁻¹, respectively. The MnVS and Co@MnVS nanoparticles obtained by green synthesis demonstrate that they are sustainable and environmentally friendly catalyst candidates for both the removal of organic pollutants such as methylene blue and hydrogen production.