Hydrogen
ion is an attractive charge carrier for energy storage
due to its smallest radius. However, hydrogen ions usually exist in
the form of hydronium ion (H3O+) because of
its high dehydration energy; the choice of electrode materials is
thus greatly limited to open frameworks and layered structures with
large ionic channels. Here, the desolvation of H3O+ is achieved by using anatase TiO2 as anodes, enabling
the H+ intercalation with a strain-free characteristic.
Density functional theory calculations show that the desolvation effects
are dependent on the facets of anatase TiO2. Anatase TiO2 (001) surface, a highly reactive surface, impels the desolvation
of H3O+ into H+. When coupled with
a MnO2 cathode, the proton battery delivers a high specific
energy of 143.2 Wh/kg at an ultrahigh specific power of 47.9 kW/kg.
The modulation of the interactions between ions and electrodes opens
new perspectives for battery optimizations.
Strain engineering is a highly effective tool for tuning the lattice parameter and in turn optimizing the optical, electronic, and chemical properties of numerous functional materials. In conventional methods, the strain is imposed from an additional heterogeneous substrate, bringing extra composition/ phase that disturbs the mechanism investigations of the effects of lattice parameters on material properties. Here, we report a convertible-precursor-induced growing method to fulfill the elongation of the uniaxial lattice parameter of anatase TiO 2 with a complex structure of single-crystal-like hierarchical arrays, without changing the composition, morphology, phase, and surface states. This methodology relies on a precursor-induced oriented growth and lattice parameter modulation on the basis of the lattice mismatch from the precursor. Unlike conventional substrate-manipulating methods, the employed precursor can be converted to the final materials (i.e., anatase TiO 2 ), which can eliminate the effects of the additional substrate. It is found that for anatase TiO 2 , the elongation of lattice parameter a leads to the shift-up of the conduction band bottom and can thus accelerate the reduction reactions of O 2 . The elongation of lattice parameter a and unique structural features make the TiO 2 arrays highly active for photocatalytic degradation of toluene in air, with a turnover frequency (TOF) 3.8 times and 2.1 times, respectively, that of the normal TiO 2 arrays and P25 powder under ultraviolet irradiation. The enhanced reduction capability is further confirmed by the much-improved efficiency to assist the photoreduction of Cr(VI) in water.
A great deal of engineering effort is focused on developing stretchable strain sensors for human motion monitoring and wearable devices. The ultrasensitivity and fast response under tiny strain (1%) while maintaining the working range remain the grand challenge. In this work, we propose an entirely stretchable strain sensor based on the sandwich sensing film, which is fabricated by vacuum filtration of silver nanowires (AgNWs)/ graphene/ AgNWs in sequence and the injection of liquid metal as electrodes. The novel sandwich sensing film endows the stretchable strain sensor high sensitivity under tiny strain (Gauge factor = 111.5 at 1%), fast response (<10 ms), relative large working range (0%–35%) with a maximum gauge factor of 1403.7, followed by good linearity, long-term durability, and the recovery property from being overstretched (>100%). The excellent performance is due to the slippage of the inner graphene under tiny strain, whereas the ‘sewing’ phenomenon of the outer AgNWs under larger strain. The sandwich structure illustrates a better combination of graphene and AgNWs than other hybrid methods, showing great potential in wearable devices and soft robotics.
Electrochromic materials are vital to the development of dual-band smart windows, which enable the individual control of visible and near-infrared (NIR) light transmittance. In this paper, we propose a novel single-component MoO3−x nanowire fabricated using a simplified preparation method via a fluoride-assisted route. The incorporation of oxygen vacancies into MoO3−x nanowire in the presence of fluoride anions has not been attempted before. Spectroscopic measurements confirm enhanced ion mobility in the MoO3−x conduction band through the Mo6+ substitution of Mo5+ cations as the origin of localized surface plasmon resonance (LSPR). Oxygen vacancies greatly improve Li+ diffusion in the MoO3−x host while providing near-infrared selective modulation due to tunable LSPR absorbance in the NIR region. The MoO3−x nanowire demonstrates excellent dual-band electrochromic performance in terms of switching speed (12.4 s and 5.4 s for coloration and bleaching between 1.0 V and 3.5 V), coloration efficiency (232.8 cm2·C−1 at 1080 nm and 211.7 cm2·C−1 at 450 nm), and electrochemical stability (91.8% at 1080 nm after 1,000 cycles). This suggests that MoO3−x nanowire with oxygen vacancy is a promising new electrochromic material for dual-band smart windows.
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