A CoAl-layered double hydroxide (LDH)@poly(3,4-ethylenedioxythiophene) (PEDOT) core/shell nanoplatelet array (NPA) is grown on a flexible Ni foil substrate as a high-performance pseudocapacitor. The LDH@PEDOT core/shell NPA shows a maximum specific capacitance of 649 F/g (based on the total mass) by cyclic voltammetry (scan rate: 2 mV/s) and 672 F/g by galvanostatic discharge (current density: 1 A/g). Furthermore, the hybrid NPA electrode also exhibits excellent rate capability with a specific energy of 39.4 Wh/kg at a current density of 40 A/g, as well as good long-term cycling stability (92.5% of its original capacitance is retained after 5000 cycles). These performances are superior to those of conventional supercapacitors and LDH NPA without the PEDOT coating. The largely enhanced pseudocapacitor behavior of the LDH@PEDOT NPA electrode is related to the synergistic effect of its individual components: the LDH nanoplatelet core provides abundant energy-storage capacity, while the highly conductive PEDOT shell and porous architecture facilitate the electron/mass transport in the redox reaction.
2243wileyonlinelibrary.com electron-hole pairs generated by unfavorable band structure greatly limits their practical applications, which is an urgent problem to be solved as well. [9][10][11] Therefore, to satisfy the requirements of water splitting, the development of new materials or methodologies to obtain effi cient photocatalysts with advantage of extended light response and an improved electronhole separation effi ciency remains a tremendous challenge.In order to enhance the water splitting performance, an effective way is to build elaborate hybrid semiconductors with high effi ciency of solar light utilization. [12][13][14] Recently, research interest on the nanostructured semiconductors is extended to 2D inorganic solids due to their large surface area and high photocatalytic effi ciency. [ 15,16 ] Layered double hydroxides (LDHs) are 2D layered anionic clays generally expressed as [M II1 -x M III x (OH) 2 ](A n− ) x/n · m H 2 O (M II and M III are divalent and trivalent metals respectively, A n− is interlayered anion). [17][18][19][20] Owing to their visible-light-response capability and large quantum yield, transition-metal-bearing LDH materials with semiconductor properties have attracted considerable attention as visible-light-induced photocatalysts. [21][22][23] However, pristine LDHs generally suffer from poor control over particle size, morphology as well as crystalline orientation, which restricts the effi ciency of charge separation and photoconversion capability. [ 24,25 ] Taking into account the fact that TiO 2 nanocrystal can act as a good acceptor for photogenerated electrons, [ 1,5 ] the hybridization of TiO 2 with LDHs would provide an effective way to enhance the charge separation and photocatalytic effi ciency. In this regard, the resulting heterostructure material would possess the following advantages: (i) prominent full sunlight utilization will be achieved owing to the combination of visible-light-active LDHs and UV-light-responsive TiO 2 ; (ii) the hierarchical structure enables a strong electronic coupling and convenient charge transfer at the interconnected interface, which would promote the separation of photoinduced electron-hole pairs.In this work, TiO 2 @CoAl-LDH core-shell nanospheres were prepared by a facile two-step route: hydrothermal synthesis of TiO 2 hollow nanospheres followed by in situ growth of CoAl-LDH shell ( Scheme 1 ). The resulting material shows extremely TiO 2 @CoAl-layered double hydroxide (LDH) core-shell nanospheres are fabricated via hydrothermal synthesis of TiO 2 hollow nanospheres followed by in situ growth of CoAl-LDH shell, which exhibit an extraordinarily high photocatalytic activity toward oxygen evolution from water oxidation. The O 2 generation rates of 2.34 and 2.24 mmol h −1 g −1 are achieved under full sunlight (>200 nm) and visible light (>420 nm), respectively, which are among the highest photocatalytic activities for oxygen production to date. The reason is attributed to the desirable incorporation of visible-light-active LDH shell with ...
Lavender layers: A poly(p-phenylene) anionic derivate and exfoliated Mg-Al layered double hydroxide monolayers were assembled into ultrathin films with well-defined blue fluorescence (see picture; the numbers indicate the number of bilayers), long-range order, and high photostability. These films work as multiple quantum-well structures for valence electrons.
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