Spotlights pubs.acs.org/JPCL
Spotlights: Volume 8, Issue 7
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DIRECTLY PROBING CHARGE SEPARATION AT INTERFACE OF TiO2 PHASE JUNCTION From marking tennis courts to making toothpaste whiter to preventing sunburn, the uses for titanium dioxide (TiO2) in everyday life are already many, but it continues to be the subject of research in a variety of fields, including photocatalysis, energy conversion and storage, and solid-state ionics. The TiO2 phase junction has been the subject of recent study, and there is growing interest in its energy band alignment and charge transfer. It is widely accepted that the small difference between energy bands in the different phases of TiO2 might be the sole driving force to control charge transfer direction and thus improve charge separation efficiency. Gao et al. (10.1021/ acs.jpclett.7b00285) probed the energy band alignment across the interface of a well defined TiO2 phase junction and found a built-in electric field up to 1 kV/cm across the rutile/anatase interface. They also used spatially resolved surface photovoltage spectroscopy and found that photogenerated electrons are transferred from rutile nanorods to anatase nanoparticles under ultraviolet light illumination. The size of anatase nanoparticles in the phase junction significantly affects the surface photovoltage and charge transfer process because of the variation of the charge depletion layer and the built-in electric field at the interface.
concentrations with x > 3 (x being Li-ion molar concentration in LixCH3NH3PbBr3) and simultaneously exhibits small structural distortions (topotactic intercalation). They describe their promising preliminary results and progress into the understanding of the storage electrochemical mechanism of nanostructured lead halide perovskite materials, which exhibit rather stable and reversible specific capacity ≈200 mA h g−1 with an excellent rate capability. The findings illustrate the outstanding electronic and ionic properties of lead halide perovskites as materials for energy storage.
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IS HIGH-DENSITY AMORPHOUS ICE SIMPLY A “DERAILED” STATE ALONG THE ICE I TO ICE IV PATHWAY? Most people have a basic knowledge of ice: In elementary school we’re taught that water, when chilled below 32 °F (0 °C), freezes and forms ice, and our drinks are the colder for it. Of course, it is not that simple. Among the many factors that affect the freezing point of water is pressure, and it has been found that ordinary ice (“ice I”) transforms into high-density amorphous ice (HDA) upon low-temperature compression, but a question has remained: Is HDA a glassy high-pressure liquid or an “ill-crystalline” material? In their Letter, Shephard et al. (10.1021/acs.jpclett.7b00492) show that HDA should be classified as a “derailed” state along the remarkable ice I to ice IV pathway and thus that it is not a glassy high-pressure liquid. The authors attribute the derailmentand hence the amorphizationto the orientational disorder of the water molecules in the ice I starting material.
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DIFFUSE LAYER EFFECT ON ELECTRON-TRANSFER KINETICS MEASURED BY SCANNING ELECTROCHEMICAL MICROSCOPY (SECM) Although the double-layer effect on electrode kinetics has been discussed for decades, there has been little reported experimental evidence because of the difficulties in measuring the rates of rapid outer-sphere electron transfer reactions. Recent theoretical and experimental studies revealed strong effects of the electrical double layer on mass transfer at nanometer-sized electrodes and in electrochemical nanogaps, and Bae et al. expand on that work in their Letter (10.1021/ acs.jpclett.7b00161). The authors report direct evidence of the electrical double-layer effect on electron-transfer kinetics at a nanoelectrode. They chose a suitable electron-transfer reaction and experimental technique to show the quantitative fit between the experimental data and simulations taking into account the double-layer effect.
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METHYLAMMONIUM LEAD BROMIDE PEROVSKITE BATTERY ANODES REVERSIBLY HOST HIGH Li-ION CONCENTRATIONS Hybrid perovskite compounds have revolutionized the field of photovoltaics and are proving to be of great use in highefficiency energy storage devices and materials. A great deal of research has been done in this area, but one thing that remains unknown is how extrinsic defects such as lithium ions interact with the hybrid perovskite structure during the charging process. Vicente and Garcia-Belmonte address this question in their Letter (10.1021/acs.jpclett.7b00189). They used the perovskite CH3NH3PbBr3 because it allows for high insertion © 2017 American Chemical Society
Published: April 6, 2017 1701
DOI: 10.1021/acs.jpclett.7b00746 J. Phys. Chem. Lett. 2017, 8, 1701−1701
