Cu-doped TiO₂ spheres: enhanced solar-driven photocatalysis for hydrogen generation and degradation of methylene blue and Congo red

Efficient photocatalysts are crucial for sustainable energy and environmental applications. In this study, Cu-doped TiO₂ microporous spheres with varying Cu concentrations (1–5 wt%) were synthesized via hydrothermal techniques for enhanced photocatalytic activity under natural sunlight. Physio-chemical characterization using UV–Vis, XRD, PL, FESEM, and XPS techniques revealed a pure anatase structure with small crystallite sizes (10–15 nm) forming porous spheres. Copper doping induced a decrease in photoluminescence intensity, suggesting improved electron–hole pair separation. Among the samples, CT-2 exhibited superior photocatalytic performance, achieving efficient hydrogen generation (1860 µmol/g/h) and degradation of cationic (methylene blue degradation of 94% in 75 min) and anionic (Congo red degradation of 97% in 14 min) dye under sunlight. However, higher Cu concentrations led to diminished photocatalytic activity, likely due to increased charge trapping and recombination. This study underscores the crucial impact of fine-tuned copper doping concentrations within the TiO₂ lattice, highlighting their crucial contribution to enhancing photocatalytic efficiency.