Waste ilmenite sludge-derived low-cost mesoporous Fe-doped TiO2: A versatile photocatalyst for enhanced visible light photocatalysis without a cocatalyst

Ilmenite (FeTiO3), a waste of the titania production industry, is proposed as a potential candidate for visiblelight-driven photocatalysis due to its narrow band gap (Eg = 2.01-2.90 eV). However, to date, its photocatalytic performance has been very poor, even significantly lower than TiO2 (Eg = 3.2 eV) due to its high iron content. Herein we report waste ilmenite sludge-derived mesoporous Fe-doped titania (m-FDT) photocatalyst with significantly enhanced activity for a variety of photocatalytic processes, including photocatalytic CO2 reduction, water splitting, and dye-degradation. The m-FDT is developed via a simple hydrothermal process and has desirable properties such as a low band gap (1.72 eV), high surface area (137 m2/g), and lower charge recombination. This can be attributed to the formation of various defects (Fe2+, Fe3+, Ti3+, and O vacancies) due to the doping of Fe in the TiO2 lattice, as confirmed by various experiments and theoretical studies. The champion photocatalyst with an optimal Fe content (1.8 wt%) exhibits high methanol production (86.1 mmol/ gcat), which is 100-fold higher than commercial TiO2 without noble metal cocatalyst and sacrificial agent. The designed photocatalyst shows excellent water-splitting activity (55.03 mu mol/gcat) and dye degradation ability. This work presents a high-performance, low-cost, versatile photocatalyst for visible light photocatalysis and opens new avenues in semiconductor photocatalysis.