Tuning the dosage of sulfuric acid to enhance TiO₂-P123-Gelatin silica photocatalyst efficiency for methylene blue degradation

This study investigates the effect of sulfuric acid volume on the photocatalytic performance of TiO₂-impregnated mesoporous silica (SPG-20) synthesized using Pluronic P123 and gelatin as structure-directing agents. Sulfonation with increasing H2SO4 volumes significantly altered the structural and catalytic properties of the materials. The sample sulfonated with 10 mL H₂SO₄ (10%TiO₂-SPG-20-SO₃H(10)) achieved the highest crystallite size (1.3 nm) and crystallinity (93%), indicating enhanced TiO₂–silica framework interaction. FTIR spectra confirmed the successful incorporation of Ti–O–Ti, Si–O–Si, Ti–O–Si, and S=O bonds. SEM-EDX analysis confirmed a fine, homogeneous particle morphology with diameters ranging from 33–47 nm. Among all tested samples, 10%TiO₂-SPG-20-SO₃H(10) achieved the highest photocatalytic degradation of methylene blue (95%), outperforming the 1 mL and 5 mL sulfonated samples (94% and 91%, respectively), as well as both template-free (88%) and template-assisted (87%) TiO₂ controls. These results underscore the critical role of optimal sulfonation in enhancing active site density and charge separation, ultimately promoting superior photocatalytic activity.