Template-free synthesis of porous TiO2/CdS for enhanced photocatalytic degradation from ilmenite

Natural mineral composite catalysts have attracted much attention due to their great potential in the fields of water treatment, air purification and energy conversion. In this study, porous TiO₂ materials were synthesized from ilmenite by a two-stage calcination and acid leaching process, and porous TiO₂/CdS composites were prepared by a hydrothermal method. The results of photocatalytic experiments indicate that the porous TiO₂/CdS composite (PTC-2) with a Ti/Cd molar ratio of 1:1 exhibits the highest photocatalytic activity, with the degradation rate of methylene blue achieving a maximum value of 96.6% at 80 min. Moreover, the composite maintains a degradation efficiency of 88.5% after five cycles. The findings demonstrate that the TiO₂/CdS heterojunction significantly enhances the photocatalyst's absorption of visible light while facilitating the effective separation and transfer of photogenerated electron–hole (e⁻/h⁺) pairs. The porous architecture of the composite facilitates superior electron transport pathways and effectively mitigates e⁻/h⁺ recombination. Furthermore, a mechanism for the photocatalytic degradation of organic dyes using porous TiO₂/CdS composites is proposed, wherein photogenerated superoxide radicals (^·O₂⁻) and hydroxyl radicals (^·OH) serve as the primary reactive species. This study explores the cost-effective synthesis of TiO₂/CdS heterojunctions and makes a significant contribution to the advancement and utilization of natural minerals for pollution degradation.