Atomically dispersed noble metal catalysts often exhibit high catalytic performances, but the metal loading density must be kept low (usually below 0.5%) to avoid the formation of metal nanoparticles through sintering. We report a photochemical strategy to fabricate a stable atomically dispersed palladium-titanium oxide catalyst (Pd1/TiO2) on ethylene glycolate (EG)-stabilized ultrathin TiO2 nanosheets containing Pd up to 1.5%. The Pd1/TiO2 catalyst exhibited high catalytic activity in hydrogenation of C=C bonds, exceeding that of surface Pd atoms on commercial Pd catalysts by a factor of 9. No decay in the activity was observed for 20 cycles. More important, the Pd1/TiO2-EG system could activate H2 in a heterolytic pathway, leading to a catalytic enhancement in hydrogenation of aldehydes by a factor of more than 55.

Novel nanowall arrays of hydrous manganese dioxide MnO2 · 0.5H2O are deposited onto cathodic substrates by the potentiostatic method from a mixed aqueous solution of manganese acetate and sodium sulfate. The deposition is induced by a change of local pH resulting from electrolysis of H2O, and hierarchical mesoporous nanowall arrays are formed as a result of simultaneous precipitation of manganese hydroxide and release of hydrogen gas bubbles from the cathode. The morphology and lithium ion intercalation properties are found to change appreciably with the concentration of the precursor electrolyte, with a significant reduction in specific surface area with an increased precursor concentration. For example, mesoporous nanowall arrays deposited from 0.1 M solution possess a surface area of ∼96 m2 g−1 and exhibit a stable high intercalation capacity of 256 mA hg−1 with a film of 0.5 µm in thickness, far exceeding the theoretical limit of 150 mA hg−1 for manganese dioxide bulk film. Such mesoporous nanowall arrays offer much greater energy storage capacity (e.g., ∼230 mA hg−1 for films of ∼2.5 µm) than that of anodic deposited films of the same thickness (∼80 mA hg−1). Such high lithium ion intercalation capacity and excellent cyclic stability of the mesoporous nanowall arrays, especially for thicker films, are ascribed to the hierarchically structured macro‐ and mesoporosity of the MnO2 · 0.5H2O nanowall arrays, which offer large surface to volume ratio favoring interface Faradaic reactions, short solid‐state diffusion paths, and freedom to permit volume change during lithium ion intercalation and de‐intercalation.

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Nanowall arrays of hydrous manganese dioxide MnO 2 · 0.5H 2 O were deposited on cathodic substrates by the potentiostatic method from a mixed aqueous solution of manganese acetate and sodium sulfate, and the Li + ions intercalation properties of such nanowall arrays were studied. The deposition was induced by a change of local pH resulting from electrolysis of H 2 O. Composition of this new nanowall structure was investigated by means of combined XRD, XPS, and TGA and determined to be hydrous manganese dioxide. SEM study revealed that the MnO 2 · 0.5H 2 O nanowall arrays were homogeneous across the entire substrate of top thicknesses that varied from 50 to 100 nm with identical depth. The nanowall arrays of hydrous manganese dioxide exhibited an initial capacity of 270 mAh/g with a reversible capacity maintained at 220 mAh/g at the 50th charge/discharge cycle in the Li + ions intercalation capacity measurement at a high charge/discharge rate of 0.1 mA/cm 2 (C/2, 76 mAh/g). This greatly enhanced Li + ions intercalation capacity is ascribed to the large active surface area of the nanowall arrays and a short facile diffusion path for Li + ions. The nanowall arrays of hydrous manganese dioxide also displayed an improved cyclic stability attributed to the reduced strain accumulated in these nanostructures during Li + ions intercalation.

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Anatase titania nanotube arrays were fabricated by means of anodization and annealed at 300, 400, and 500°C in N 2 . Lithium-ion intercalation measurements revealed that annealing in nitrogen resulted in much enhanced lithium-ion insertion capacity and improved cyclic stability. TiO 2 nanotube arrays annealed at 300°C exhibited the best lithium-ion intercalation property with an initial high discharge capacity up to 240 mA · h/g at a high current density of 320 mA/g. The excellent discharge capacity at a high charge/discharge rate could be attributed to the large surface area of the nanotube arrays and a short facile diffusion path for lithium-ion intercalation as well as improved electrical conductivity. As the annealing temperature increased, the discharge capacity decreased, but the cyclic stability improved; 400°C annealed TiO 2 nanotube arrays possessed an initial discharge capacity of 163 mA · h/g and retained 145 mA · h/g at the 50th cycle. The relationship between the annealing conditions, microstructure, and lithium-ion intercalation properties of TiO 2 nanotube arrays was discussed.

A method with exceptional comprehensive performance for gold nanorod synthesis using 3-aminophenol as the reducing agent.

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