Enhanced photocatalytic activity of ultrahigh-surface-area TiO2@C nanorod aggregates with hierarchical porosities synthesized from natural ilmenite

[Display omitted] •TiO2@C nanorod aggregates were synthesized from natural ilmenite and activated carbon.•Through the addition of carbon and calcination, the formation of hierachical pore structure appears.•Photocatalytic performace improved by high-surface-area and hierarchical pore structure.•Photocatalytic performance of TiO2@C-700 is maintained over 100 repeated cycles under visible light. Cost-effective methods to produce effective TiO2 photocatalytic materials for degrading organic pollutants are in high demand. Herein, we present an approach to enhancing the photocatalytic activity of TiO2@C nanorod-aggregate catalysts with an ultrahigh surface area and hierarchical pore structure synthesized from natural ilmenite using mechanical activation, annealing, HCl leaching, and calcination. The photocatalytic activity of the catalysts was analyzed for degrading methylene blue under UV and visible light irradiation. Leaching in the presence of HCl formed TiO2 nanorods containing micropores with a large specific surface area (876 m2/g). Further calcination led to the formation of hierarchical mesoporous structures by aggregation of the nanorods. TiO2@C calcined at 700 °C (TiO2@C-700), with its high crystallinity and improved pore structure, possessed an excellent adsorption capacity and a reaction rate constant (k) of 0.0631 min-1 under visible light. The enhanced photocatalytic performance of the catalyst despite its rutile phase is attributable to the large surface area offering more active sites and the hierarchical pore structure, which facilitates mass transport and a high crystallinity. In addition, the durability of TiO2@C-700 was evaluated under visible light irradiation for 100 cycles, and the k value and decomposition efficiency at 60 min were retained at 88.8 % and 92.0 % respectively, as compared with the first cycle. Therefore, we believe that the proposed strategy provides an efficient way to overcome the economic aspects that limit the industrial application of porous TiO2-based catalysts.