Nano-p–n junctions on surface-coarsened TiO2 nanobelts with enhanced photocatalytic activity

Nano-p–n junction heterostructure TiO2 nanobelts have been produced by assembling p-type semiconductor NiO nanoparticles on n-type TiO2 nanobelts for enhancement of the photocatalytic properties of TiO2 nanobelts. NiO/TiO2 nano-p–n junctions were synthesized on the surfaces of TiO2 nanobelts and surface-coarsened TiO2 nanobelts. The nanobelts were obtained using alkaline- and acid-assisted hydrothermal processes. The chemical-solution-deposition–decomposition process was used to form NiO nanoparticle/TiO2 heterostructure composite nanobelts (NiO-NP/TiO2 NBs), and NiO nanoparticle/surface-coarsened TiO2 heterostructure composite nanobelts (NiO-NP/TiO2 coarsened NBs). The uniform assembly of p-type NiO nanoparticles produces a large number of nano-p–n junction heterostructures on the surface of the TiO2 nanobelts, where NiO and TiO2 form p- and n-type semiconductors, respectively. Compared with both pure NiO nanoparticles and TiO2 nanobelts, NiO-NP/TiO2 NBs exhibit much enhanced photocatalytic activity. Interestingly, the optimized composite NiO-NP/TiO2 coarsened NBs exhibit an enhanced photocatalytic activity in the decomposition of a model dye compound, methyl orange (MO), under both ultraviolet and visible light irradiation. It is argued that the nano-p–n junctions effectively reduce the recombination of electrons and holes, thus leading to the enhancement of the photocatalytic properties of the heterostructure composites. The larger number of abundant photocatalytic-active surfaces in the surface-coarsened nanobelts increases photo-absorption and the production of charge carriers, which gives the composites an enhanced photocatalytic performance. The established approach allows for controlling the nano-p–n junction heterostructure of the nanobelts, and hence, their photocatalytic effect. The NiO/TiO2 nanobelt-based nano-p–n junction heterostructure TiO2 can provide a practical way to design and prepare nano-composites for applications as solar-cell electrodes, in solar photocatalysis, solar photolysis of water and other related fields.