Rutile TiO2 nanocrystals with exposed high-index facets have been investigated in detail by high resolution transmission electron microscopy (HR-TEM) and selected-area electron diffraction (SAED). It was found that the each branched nanocrystal is bound by 4 facets of high-index {331). Additionally, rutile {101) twinned structures are formed in the boundary of branches during the growth of multi branches in a hierarchical flower-like nanostructures. Notably, the synthesized nanostructures showed significantly higher photocatalytic activities than that of rod particles with exposed {110) facets in photocatalytic CO2 reduction. Correlating the presence of high-energy surface on rutile nanocrystals with the photocatalytic activity clearly shows the significant role of surface steps in enhancing intrinsic activity for CO2 reduction to methanol. (C) 2017 Elsevier Inc. All rights reserved.