Owing to its high charge-carrier mobility, tunable direct-bandgap and unique in-plane anisotropic structure, black phosphorus (BP), a rising star of post-graphene two-dimensional (2D) nanomaterials, has been intensively investigated since early 2014. To explore its full potential and push the limits, research into BP-based novel functional nanostructures (i.e., nanomaterials and nanodevices) by means of hybridization, doping, and functionalization is rapidly expanding. Indeed, the cutting-edge developments and applications of BP nanostructures have had a significant impact on a wide range of research areas, including field effect transistors, diodes, photodetectors, biomedicine, sodium-ion batteries, photocatalysis, electrocatalysis, memory devices, and more. This tutorial review summarizes the recent advances of BP nanostructures and outlines the future challenges and opportunities.

Gold (Au) nanoparticles (NPs) supported on well-defined ceria (CeO2) nanorods with exposed {110} and {100} facets were prepared by a deposition-precipitation method and characterized by powder X-ray diffraction, micro-Raman spectroscopy, X-ray photoelectron spectroscopy, nitrogen adsorption-desorption, transmission electron microscopy, high-resolution transmission electron microscopy, and high-angle annular dark-field scanning transmission electron microscopy. Both nanometer and subnanometer gold particles were found to coexist on ceria supports with various Au contents (0.01-5.4 wt %). The catalytic performance of Au/CeO2 catalysts was examined for formaldehyde (HCHO) oxidation into CO2 and H2O at room temperature and shown to be Au content dependent, with 1.8 wt % Au/CeO2 displaying the best performance. On the basis of the results from hydrogen temperature-programmed reduction and in situ Fourier transform infrared spectroscopy observations, the high reactivity and stability of Au/CeO2 catalysts is mainly attributed to the well-defined ceria nanorods with {110} and {100} facets which present a relatively low energy for oxygen vacancy formation. Furthermore, gold NPs could induce the weakened Ce-O bond which in turn promotes HCHO oxidation.

Structure-function correlations are a central theme in heterogeneous (photo)catalysis. In this study, using aberration-corrected scanning transmission electron microscopy (STEM), the atomic surface structures of well-defined one-dimensional (1D) CeO 2 nanorods (NRs) and 3D nanocubes (NCs) are directly visualized at subangstrom resolution. CeO 2 NCs predominantly expose {100} facet, with {110} and {111} as minor cutoff facets at the respective edges and corners. Notably, the outermost surface layer of {100} facet is nearly O terminated. Neither surface relaxations nor reconstructions on {100} are observed, indicating unusual polarity compensation, which is primarily mediated by near-surface oxygen vacancies. In contrast, the surface of CeO 2 NRs is highly stepped, with the enclosed {110} facet exposing Ce cations and O anions on terraces. On the basis of STEM profile-view imaging and electronic structure analysis, the photoreactivity of CeO 2 nanocrystals toward aqueous methyl orange degradation under UV is revealed to be surface-structure-sensitive, following the order: {110} » {100}. The underlying surface structure-sensitivity can be attributed to the variation in lowcoordinate surface cerium cations between {110} and {100} facets. To further enhance light absorption, Au nanoparticles (NPs) were deposited on CeO 2 NRs to form Au/CeO 2 plasmonic nanocomposites, which dramatically promotes the photoreactivity that is Au particle size-and excitation light wavelength-dependent. The mechanisms responsible for the enhancement of photocatalytic activity were discussed, highlighting the crucial role of photoexcited charge carrier transfer.