Nanostructured N-doped TiO₂ marigold flowers for an efficient solar hydrogen production from H₂S

Nitrogen-doped TiO₂ nanostructures in the form of marigold flowers have been synthesized for the first time using a facile solvothermal method. The structural analysis has shown that such an N-doped TiO₂ system crystallizes in the anatase structure. The optical absorption spectra have clearly shown the shift in the absorption edge towards the visible-light range, which indicates successful nitrogen doping. The nitrogen doping has been further confirmed by photoluminescence and photoemission spectroscopy. Microscopy studies have shown the thin nanosheets (petals) of N-TiO₂ with a thickness of ∼2-3 nm, assembled in the form of the marigold flower with a high surface area (224 m(2) g(-1)). The N-TiO₂ nanostructure with marigold flowers is an efficient photocatalyst for the decomposition of H₂S and production of hydrogen under solar light. The maximum hydrogen evolution obtained is higher than other known N-TiO₂ systems. It is noteworthy that photohydrogen production using the unique marigold flowers of N-TiO₂ from abundant H2S under solar light is hitherto unattempted. The proposed synthesis method can also be utilized to design other hierarchical nanostructured N-doped metal oxides.