Surfactant plays a remarkable role in determining the growth process (facet exposition) of colloidal nanocrystals (NCs) and the formation of self-assembled NC superstructures, the underlying mechanism of which, however, still requires elucidation. In this work, the mechanism of surfactant-mediated morphology evolution and self-assembly of CeO2 nanocrystals is elucidated by exploring the effect that surfactant modification has on the shape, size, exposed facets, and arrangement of the CeO2 NCs. It is directly proved that surfactant molecules determine the morphologies of the CeO2 NCs by preferentially bonding onto Ce-terminated {100} facets, changing from large truncated octahedra (mostly {111} and {100} exposed), to cubes (mostly {100} exposed) and small cuboctahedra (mostly {100} and {111} exposed) by increasing the amount of surfactant. The exposure degree of the {100} facets largely affects the concentration of Ce3+ in the CeO2 NCs, thus the cubic CeO2 NCs exhibit superior oxygen storage capacity and excellent supercapacitor performance due to a high fraction of exposed active {100} facets with great superstructure stability.
The tetragonal phase Nb 2 O 5 (T-Nb 2 O 5 ) nanobelts with preferentially exposed the (010) facet have been successfully prepared for the first time by insitu topological reaction using the KNb 3 O 8 nanobelts as the precursor. Meanwhile, the transformation mechanism of the crystal structure and morphology from the layered KNb 3 O 8 nanobelt to the T-Nb 2 O 5 nanobelt was revealed in detail by using XRD, FE-SEM, TEM, HRTEM, SAED, UV-vis DRS, EDX, XPS, and Raman spectra. In addition, Ag deposited T-Nb 2 O 5 (Ag/T-Nb 2 O 5 ) nanobelts were prepared by photo-reduction reaction. The photoelectrochemical properties of the T-Nb 2 O 5 nanobelts and Ag/T-Nb 2 O 5 nanobelts as a photocatalyst were evaluated by splitting water under simulated sunlight. The results show that the photocurrent density generated by the prepared Ag/T-Nb 2 O 5 sample is 48.1 µA∙cm −2 , which is 2.3 times that of the T-Nb 2 O 5 sample, and the prepared tetragonal phase T-Nb 2 O 5 nanobelts produce a photocurrent value 1.5 times that of the contrast orthogonal phase O-Nb 2 O 5 nanosheets. It indicates that the (010) facet of the tetragonal phase Nb 2 O 5 is one of the highest photocatalytic active surfaces, and the visible light utilization efficiency of the T-Nb 2 O 5 nanobelt with Ag deposited on the surface has been significantly improved, which implies that it has potential applications in the field of photocatalysis.
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