Intercalation-type TiNbO (x = 2, 5, and 24) anode materials have recently become more interesting for lithium-ion batteries (LIBs) due to their large theoretical capacities of 388-402 mAh g. However, the Ti/Nb ions in TiNbO with empty 3d/4d orbitals usually lead to extremely low electronic conductivity of <10 S cm, greatly restricting their practical capacity and rate capability. Herein, we report a class of highly conductive CrNbO nanowires as an intercalation-type anode material for high-performance LIBs. The as-made CrNbO nanowires show an open shear ReO crystal structure (C2 space group) with 4% tetrahedra and a conducting characteristic with ultrahigh electronic conductivity of 3.6 × 10 S cm and a large Li-ion diffusion coefficient of 2.19 × 10 cm s. These important characteristics make them deliver outstanding electrochemical properties in term of the largest reversible capacity (344 mAh g at 0.1 C) in all the known niobium- and titanium-based anode materials, safe working potential (∼1.65 V vs Li/Li), high first-cycle Coulombic efficiency (90.8%), superior rate capability (209 mAh g at 30 C), and excellent cycling stability, making them among the best for LIBs in niobium- and titanium-based anode materials.

Anatase hierarchical TiO2 with innovative designs (hollow microspheres with exposed high-energy {001} crystal facets, hollow microspheres without {001} crystal facets, and solid microspheres without {001} crystal facets) were synthesized via a one-pot hydrothermal method and characterized. Based on these materials, gas sensors were fabricated and used for gas-sensing tests. It was found that the sensor based on hierarchical TiO2 hollow microspheres with exposed high-energy {001} crystal facets exhibited enhanced acetone sensing properties compared to the sensors based on the other two materials due to the exposing of high-energy {001} crystal facets and special hierarchical hollow structure. First-principle calculations were performed to illustrate the sensing mechanism, which suggested that the adsorption process of acetone molecule on TiO2 surface was spontaneous, and the adsorption on high-energy {001} crystal facets would be more stable than that on the normally exposed {101} crystal facets. Further characterization indicated that the {001} surface was highly reactive for the adsorption of active oxygen species, which was also responsible for the enhanced sensing performance. The present studies revealed the crystal-facets-dependent gas-sensing properties of TiO2 and provided a new insight into improving the gas sensing performance by designing hierarchical hollow structure with special-crystal-facets exposure.

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