Cu-doped TiO2 nanostructures for photocatalytic removal of Rhodamine B and catalytic H2 evolution

Abstract

Semiconductor-based catalysis has become a promising approach to address environmental pollution and sustainable energy production. This thesis presents the synthesis, characterization, and catalytic evaluation of Cu-doped TiO2 nanostructures obtained by the solvothermal method with several copper concentrations. ICP-OES showed that the experimental copper contents (2.148% and 2.764%) were lower than the theoretical values (2.68 ± 0.01% and 5.20 ± 0.03%), indicating partial incorporation into the TiO2 lattice. SEM and TEM confirmed quasi-spherical nanoparticles (10-60 nm) with slight agglomeration typical of metal oxide nanomaterials. HR-TEM analysis revealed lattice spacings corresponding to the TiO2 anatase phase (101), confirming the preservation of the crystal structure during doping. X-ray diffraction analysis also confirmed that both samples crystallize in the anatase phase. XPS analysis revealed the presence of Ti+4 and significantly reduced copper particles (Cu0/Cu+) without Cu2+ satellite peaks. The BET analysis demonstrated mesoporous structures with type IV isotherms with H2 hysteresis loops. Sample A had a higher surface area (110.7 m2/g) than Sample B (94.9 m2/g), while increased copper content led to larger pore size and volume. Optical studies have shown a decrease in the band gap from 3.14 eV (Sample A) to 2.93 eV (Sample B) due to an increase in the copper content. Rhodamine B degradation reached 81.18% for Sample B, representing the best performance, attributed to its reduced band gap. This may lead to enhanced generation of hydroxyl radicals from H2O2. Experiments on hydrogen evolution confirmed the increased catalytic activity of Cu-doped TiO2 samples compared with pure NaBH4. Sample B also exhibited the best performance in hydrogen evolution. Activation energy calculations showed values of 43.94 ± 0.48 kJ/mol (Sample A), 56.26 ± 8.13 kJ/mol (Sample B), and 30.4 ± 7.35 kJ/mol for pure NaBH4. These results highlight the potential of optimized Cu-doped TiO2 as an efficient and multifunctional catalyst. Current and future research, including detailed hydrogen evolution measurements and structural analysis, aims to further elucidate the relationship between synthesis condition and catalytic activity.