Biomineralized N-Doped CNT/TiO2 Core/Shell Nanowires for Visible Light Photocatalysis

We report an efficient and environmentally benign biomimetic mineralization of TiO2 at the graphitic carbon surface, which successfully created an ideal TiO2/carbon hybrid structure without any harsh surface treatment or interfacial adhesive layer. The N-doped sites at carbon nanotubes (CNTs) successfully nucleated the high-yield biomimetic deposition of a uniformly thick TiO2 nanoshell In neutral pH aqueous media at ambient pressure and temperature and generated N-doped CNT (NCNT)/TiO2 core/shell nanowires. Unlike previously known organic biomineralization templates, such as proteins or peptides, the electroconductive and high-temperature-stable NCNT backbone enabled high-temperature thermal treatment and corresponding crystal structure transformation of TiO2 nanoshells into the anatase or rutile phase for optimized material properties. The direct contact of the NCNT surface and TiO2 nanoshell without any adhesive interlayer introduced a new carbon energy level in the TiO2 band gap and thereby effectively lowered the band gap energy. Consequently, the created core/shell nanowires showed a greatly enhanced visible light photocatalysis. Other interesting synergistic properties such as stimuli-responsive wettabilites were also demonstrated.