Different-sized CdSe quantum dots have been assembled on TiO2 films composed of particle and nanotube morphologies using a bifunctional linker molecule. Upon band-gap excitation, CdSe quantum dots inject electrons into TiO2 nanoparticles and nanotubes, thus enabling the generation of photocurrent in a photoelectrochemical solar cell. The results presented in this study highlight two major findings: (i) ability to tune the photoelectrochemical response and photoconversion efficiency via size control of CdSe quantum dots and (ii) improvement in the photoconversion efficiency by facilitating the charge transport through TiO2 nanotube architecture. The maximum IPCE (photon-to-charge carrier generation efficiency) obtained with 3 nm diameter CdSe nanoparticles was 35% for particulate TiO2 and 45% for tubular TiO2 morphology. The maximum IPCE observed at the excitonic band increases with decreasing particle size, whereas the shift in the conduction band to more negative potentials increases the driving force and favors fast electron injection. The maximum power-conversion efficiency

A new gas-utilizing battery using mixed gas of O(2) and CO(2) was developed and proved its very high discharge capacity. The capacity reached three times as much as that of a non-aqueous Li-air (O(2)) battery. The unique point of the battery is expected to be the rapid consumption of superoxide anion radical by CO(2) as well as the slow filling property of the Li(2)CO(3) in the cathode.

Portable power sources and grid-scale storage both require batteries combining high energy density and low cost. Zinc metal battery systems are attractive due to the low cost of zinc and its high charge-storage capacity. However, under repeated plating and stripping, zinc metal anodes undergo a well-known problem, zinc dendrite formation, causing internal shorting. Here we show a backside-plating configuration that enables long-term cycling of zinc metal batteries without shorting. We demonstrate 800 stable cycles of nickel–zinc batteries with good power rate (20 mA cm−2, 20 C rate for our anodes). Such a backside-plating method can be applied to not only zinc metal systems but also other metal-based electrodes suffering from internal short circuits.

attractive approach to reach high energy density; however, the previously reported study has an environmental concern due to the use of heavy metals and lower energetic density caused by the bulky cations. [ 3 ] In addition, the liquids should have a stable fl uidic property even in a low temperature range without freezing, especially for automobile applications.Here, we propose to change the strategy from maximizing the solubility of redox compounds to minimizing the dissolving solvents (Figure 1 a, right side). The minimum requirements for the catholyte are stoichiometric couples of a redox species and appropriate supporting salt. Because the valence of the redox species must be changed during discharging and charging, compensating ions must be present in the system. Therefore, a redox couple with a single valence change (i.e., A/A + , A − /A, or A + /A ++ ) requires the same molar of monovalent salt (i.e., X + B − ), and their 1:1 molar mixture yields the maximum electronic capacity for batteries. The challenge is then determining how to liquefy this couple. First, we selected 4-methoxy-2,2,6,6-tetramethylpiperidine 1-oxyl ( MT or MeO-TEMPO) as a redox compound. MT has excellent chemical, physical, and electrochemical stability, [4] similar to non-substituted TEMPO, [ 5 ] and also has a low melting point ( T m ) (42 °C). Next, we focused on lithium bis(trifl uoromethanesulfonyl) imide ( LT or LiTFSI) as a supporting salt because TFSI anion was one of the most interesting ions with an unusual plasticizing effect, which often realized low T m mixtures, [ 6 ] plastic crystals [ 7 ] and supercooled liquids, whereas the T m of LT was rather high (230 °C). In previous studies, the unique effect has been understood by the weak Lewis-basic property due to its charge delocalization and isoenergetic conformation change. [ 8 ] Then, as shown in Figure 1 b (right side), a simple 1:1 molar mixture of MT and LT exhibited a self-melting behavior and formed a smooth viscous liquid. Finally, by the addition of small amount of an appropriate solvent (i.e., acetonitrile (ACN), water, etc.) a highly concentrated (over 2 M ) and low-viscosity liquid could be prepared (Figure 1 b, center). In this report, the mixture of MT and LT with molar ratios of x and y , respectively, will be described as " MTLT ( x / y )." For example, MTLT (1/1) denotes a 1:1 molar mixture of MT and LT . Mixtures ranging from MTLT (1/1) to MTLT (20/1) are found to yield orangecolored smooth liquids at room temperature. Because i) a series of sulfonylimide-based salts, such as Li bis(fl uorosulfonyl) imide (LiFSI) or Li bis(pentafl uoroethanesulfonyl) imide (LiBETI), exhibit similar properties and ii) other inorganic Li-salts, such as LiPF 6 , or LiBF 4 , do not exhibit this unique feature (Figure 1 b, left), the sulfonylimide structure could be critical to understanding this unique property. With regard to TEMPO, even non-substituted TEMPO forms a similar liquid when mixed with LT ; however, the liquid phase is not stable can be crystallized more easi...

It is widely acknowledged that Li 2 CO 3 and LiOH as sideproducts in the operation of a Li−air cell should be completely removed in the cycling to avoid cumulative negative effect on the cycling performance. However, the understanding of their electrochemical decomposition is limited. We report a mechanistic analysis of the intrinsic barrier to electrochemically decompose Li 2 CO 3 and LiOH. Our first-principles study reveals that the decomposition is rate-limited by the electrochemical extraction of Li + , whereas the chemical release of anions is barrierless once the applied voltage overcomes the energy penalty to generate a Li-deficient surface. The voltage necessary for the decomposition of Li 2 CO 3 is predicted to be in the range of 4.38−4.61 V, whereas for LiOH it is in the range of 4.67−5.02 V. The maximum charge efficiency to decompose Li 2 CO 3 and LiOH in the operation of a Li−air cell is estimated to be 66% and 61%, respectively. The high intrinsic barrier originates from the energy cost of oxidizing redox-inert anions for the charge neutrality when lithium is extracted. Therefore, one strategy for lowering the barrier is incorporating redox-active species as a charge mediator to compensate the electron loss during the decomposition.