No abstract

A simple method has been developed to substantially improve the high‐rate capability of electrochemically anodized TiO2 nanotube arrays targeted for use as anode material in lithium‐ion microbatteries by annealing in a reducing atmosphere (5 % H2 and 95 % Ar). A series of complementary techniques including X‐ray diffraction (XRD) with Rietveld refining, scanning electron microscopy (SEM), high‐resolution transmission electron microscopy (HRTEM), X‐ray photoelectron spectroscopy (XPS), Raman spectrometry (Raman), Fourier‐transform infrared spectroscopy (FTIR), galvanostatic measurements, and electrochemical impedance spectroscopy (EIS) have been employed to investigate the structural and morphological changes as well as the electrochemical performance enhancement resulting from hydrogenation treatment of the TiO2 nanotube arrays. The results reveal that improvement of the rate capability is mainly attributed to the electronic conductivity increase of the bulk TiO2 nanotubes rather than conductive characteristics of the surface coating because hydrogenation treatment produces a high number of oxygen vacancies inside the crystal lattices that makes the TiO2 nanotube arrays favor a bulk n‐type conductor. Furthermore, the high‐rate capability of other kinds of TiO2 nanomaterials, including rutile TiO2 nanowire arrays and anatase TiO2 nanoparticles, can also be considerably improved by similar H2 treatment. Therefore, the current H2 treatment method is proved to be a general and facile technique to improve the power density of TiO2 anode materials for next‐generation, high‐power lithium‐ion batteries.

The synthesis, characterization, and photophysics of a series of solution-processable and strongly visible-light absorbing platinum(II) polyynes containing bithiazole-oligo(thienyl) rings were presented. Tuning the polymer solar cell efficiency, as well as optical and charge transport properties, in soluble, low-band gap PtII-based conjugated poly(heteroaryleneethynylene)s using the number of oligothienyl rings is described. These materials are highly soluble in polar organic solvents due to the presence of solubilizing bithiazole moieties and show strong absorptions in the solar spectra, rendering them excellent candidates for bulk heterojunction polymer solar cells. Their photovoltaic responses and power conversion efficiencies (PCEs) depend to a large extent on the number of thienyl rings along the main chain, and some of them can be used to fabricate highly efficient solar cells with PCEs of up to 2.7% and a peak external quantum efficiency to 83% under AM1.5 simulated solar illumination, which is comparable to that of poly(3-hexylthiophene)-based devices fabricated without additional processing (annealing or TiO(x) layer). The influence of the number of thienyl rings and the metal group on the performance parameters and optimization of solar cell efficiency was evaluated and discussed in detail. At the same blend ratio of 1:4, the light-harvesting ability and PCE increase sharply as the thienyl chain length increases. The present work provides an attractive approach to developing conjugated metallopolymers offering broad solar absorptions and tunable solar cell efficiency and demonstrates the potential of metalated conjugated polymers for efficient power generation.