Kinetically Controlled Fabrication of Single-Crystalline TiO2 Nanobrush Architectures with High Energy {001} Facets

Femtosecond Laser Induced Phase Transformation of TiO2 with Exposed Reactive Facets for Improved Photoelectrochemistry Performance

Titanium dioxide (TiO₂) is one of the most promising candidates for photoelectrochemistry applications. For a high photoelectrochemistry performance, the control of crystal structure and crystal facet is essential. The phase transformation of TiO₂ is conventionally achieved by thermal annealing. Here, we report an approach for selective phase transformation of TiO₂ containing exposed reactive facets with improved photoelectrochemistry performance. After femtosecond laser processing, TiO₂ nanotubes with exposed reactive anatase {010} facets are prepared, and they have a maximum photocurrent density more than 5 times that of pure anatase. Additionally, this strategy can induce phase transformation in a selective area, which shows the advantages of patterning processing. Our method constructs a promising strategy for preparing functional nanomaterials with high performances and functionality.

Vertically Aligned Single-Crystalline CoFe2O4 Nanobrush Architectures with High Magnetization and Tailored Magnetic Anisotropy

Micrometer-tall vertically aligned single-crystalline CoFe₂O₄ nanobrush architectures with extraordinarily large aspect ratio have been achieved by the precise control of a kinetic and thermodynamic non-equilibrium pulsed laser epitaxy process. Direct observations by scanning transmission electron microscopy reveal that the nanobrush crystal is mostly defect-free by nature, and epitaxially connected to the substrate through a continuous 2D interface layer. In contrast, periodic dislocations and lattice defects such as anti-phase boundaries and twin boundaries are frequently observed in the 2D interface layer, suggesting that interface misfit strain relaxation under a non-equilibrium growth condition plays a critical role in the self-assembly of such artificial architectures. Magnetic property measurements have found that the nanobrushes exhibit a saturation magnetization value of 6.16 B/f.u., which is much higher than the bulk value. The discovery not only enables insights into an effective route for fabricating unconventional high-quality nanostructures, but also demonstrates a novel magnetic architecture with potential applications in nanomagnetic devices.

Atomic Layers of MoO2 with Exposed High-Energy (010) Facets for Efficient Oxygen Reduction

Although 2D nanocrystals with exposed high-energy facets are highly desired in the field of catalysts due to their anticipant high catalytic activities, they are difficult to be gained. Here, atomic layers of metallic molybdenum dioxide (MoO₂ ) with primarily exposed high-energy (010) facet are achieved via a facile carbothermic reduction approach. The resultant MoO₂ exhibits single-crystalline, monoclinic, and ultrathin features with nearly 100% exposed (010) facet, which can significantly reduce reaction barriers toward the oxygen reduction reaction. As a consequence, the atomic layers of MoO₂ exhibit high electrocatalytic activity, excellent tolerance to methanol, and good stability for the oxygen reduction reaction in alkaline electrolyte, superior to commercial Pt/C catalysts. It is believed that such new transition metal oxide catalysts with exposed high-energy facets have broad applications in the areas of energy storage and conversions.