Effect of nature and location of defects on bandgap narrowing in black TiO 2 nanoparticles

he increasing need for new materials capable of solar fuel generation is central in the development of a green energy economy. In this contribution, we demonstrate that black TiO 2 nanoparticles obtained through a one-step reduction/crystallization process exhibit a bandgap of only 1.85 eV, which matches well with visible light absorption. The electronic structure of black TiO 2 nanoparticles is determined by the unique crystalline and defective core/disordered shell morphology. We introduce new insights that will be useful for the design of nanostructured photocatalysts for energy applications.