Natural down fiber as a green dopant for high-efficiency C–N–Cu co-doped TiO2 in visible-light photocatalysis

Doping has been widely explored as an effective strategy to enhance the photocatalytic performance of TiO 2 under visible light for degrading organic pollutants. However, conventional dopants derived from chemical reagents raise environmental and human safety concerns. In this study, natural down fiber (DF) was innovatively employed as a sustainable and green source of C and N, combined with copper acetate as the copper source, to fabricate C–N–Cu co-doped TiO 2 (C–N–Cu@TiO 2 ) via a facile one-step hydrothermal method. Comprehensive characterization revealed that, compared to pure TiO 2 , the co-doped C–N–Cu@TiO 2 exhibited a narrowed band gap (from 3.11 to 2.83 eV), reduced photoluminescence intensity, and enhanced photocurrent density, indicating improved visible-light absorption and effective suppression of electron–hole recombination. Under simulated one-sun irradiation, C–N–Cu@TiO 2 demonstrated outstanding photocatalytic activity, achieving a high degradation efficiency of 98.20% for methyl orange within 2 h, which is competitive with many reported doped TiO 2 photocatalysts. Trapping experiments identified O 2 − and h + as the primary active species, and a plausible photocatalytic mechanism was proposed accordingly. This work not only confirms the effectiveness of natural DF as an eco-friendly and sustainable doping source, but also encourages further exploration of biomass-derived functional materials for applications in wastewater treatment, photocatalytic hydrogen evolution, carbon dioxide reduction, and related fields.