Waste-derived CaO Modified TiO₂ with Reduced Band Gap and Improved Photoresponse under Visible Light

Siti Rodiah (Department of Chemistry, Universitas Islam Negeri Raden Fatah Palembang, Palembang-30267 (Indonesia))
Ratih Rizqi Nirwana (Department of Chemistry, Universitas Islam Negeri Walisongo, Semarang 50216 (Indonesia))
Desti Erviana (Department of Chemistry, Universitas Islam Negeri Raden Fatah Palembang, Palembang-30267 (Indonesia))
Nina Ariesta (Department of Chemistry, Universitas Nusa Bangsa, Bogor 16166 (Indonesia))
Damayanti Iskandar (Department of Chemistry, Universitas Islam Negeri Raden Fatah Palembang, Palembang-30267 (Indonesia) Departement Biomaterial, Okayama University, Okayama-7008530 (Japan))
Hapin Afriyani (Department of Chemistry, Lampung University, Bandar Lampung-35141 (Indonesia))

Journal of Multidisciplinary Applied Natural Science
Vol. 6 No. 3 (2026): Journal of Multidisciplinary Applied Natural Science

Titanium dioxide (TiO₂) is the most extensively investigated photocatalysts, but its high band gap energy limits its photoactivity primarily to the ultraviolet region. This study presents a green approach to enhanced visible-light absorption of TiO₂ by utilizing calcined golden snail shells as a sustainable and low-cost precursor for CaO dopant. The TiO₂-CaO composites were synthesized via a simple loading technique. Characterization confirmed the successful distribution of CaO onto the TiO₂ surface, reducing in the band gap energy of TiO₂ from 3.334 eV to 3.322 eV. This modification substantially broadened the material’s light absorption into the visible spectrum. The optimized composites demonstrated feasible photocatalytic activity for the reduction of CO₂ under simulated solar irradiation with the addition of Clitoria ternatea photosensitizer, achieving initial activity higher than that of pure TiO₂. This work successfully combines the waste-derived CaO, offering a promising, environmentally friendly, and highly effective green material to improved photoresponse under visible light of TiO₂.