No abstract

No abstract

LiMn2O4 is of great potential for selectively extracting Li+ from brines and seawater, yet its application is hindered by its poor cycle stability and conductivity. Herein a two‐step strategy to fabricate highly conductive and stable CNT‐strung LiMn2O4 (CNT‐s‐LMO) is reported, by first stringing Mn3O4 particles with multiwalled carbon nanotube (CNT), then converting the hybrids into CNT‐s‐LMO through hydrothermal lithiation. The as‐synthesized CNT‐s‐LMO materials have a net‐like structure with CNTs threading through LMO particles. This unique structure has endowed the CNT‐s‐LMO electrode with excellent conductivity, high specific capacitance, and enhanced rate performance. Because of this, the CNT‐s‐LMO electrode in the hybrid capacitive deionization cell (HCDI) can deliver a high Li+ extraction percentage (≈84%) in brine and an outstanding lithium selectivity with a separation factor of ≈181 at the Mg2+/Li+ molar ratio of 60. Significantly, the CNT‐s‐LMO‐based HCDI cell has a high stability, evidenced by 90% capacity retention and negligible Mn loss in 100 cycles. This method has paved a new way to fabricate carbon‐enabled LMO‐based absorbents with tuned structure and superior capacity for electrochemical lithium extraction with high Li+ selectivity and exceptional cycling stability, which may help to tackle the shortage in supply of Li‐ion batteries in industry in the future.

No abstract

No abstract

We have reported a theoretical analysis of a series of heteroleptic iridium(III) complexes (mpmi)2Ir(fppi) [mpmi = 1-(4-tolyl)-3-methyl-imidazole, fppi = 4-fluoro-2-(pyrrol-2-yl)-pyridine] (1a), (mpmi)2Ir(dfpi) [dfpi = 4-fluoro-2-(3-fluoro-pyrrol-2-yl)-pyridine] (1b), (mpmi)2Ir(tfpi) [tfpi = 2-(pyrrol-2-yl)-4-trifluoromethyl-pyridine] (1c), (mpmi)2Ir(priq) [priq = 1-(pyrrol-2-yl)isoquinoline] (2a), (mpmi)2Ir(isql) [isql = 1-(indol-2-yl)-isoquinoline] (2b), and (mpmi)2Ir(biql) [biql = 1-(benzoimidazol-2-yl)-isoquinoline] (2c) by using the density functional theory (DFT) method to investigate their electronic structures, photophysical properties, and the phosphorescent efficiency mechanism. The results reveal that the nature of the ancillary ligands can affect the electron density distributions and energies of frontier molecular orbitals, resulting in changes of charge transfer performances and emission color. It is found that the studied complex 1c with the -CF3 substituent at the pyridine moiety results in the lower HOMO-LUMO energy gap and LUMO energy level, which will lead to a rich electron injection ability compared with that of 1a. For each complex studied (except 2b), the hole-transporting performance is better than the electron-transporting performance. In addition, for complexes 2a and 2b, the differences between reorganization energies for hole transport (λ(ih)) and reorganization energies for electron transport (λ(ie)) are relatively smaller, indicating that the hole and electron transfer balance could be achieved more easily in the emitting layer. It is believed that the largest metal to ligand charge transfer (MLCT) character, the higher μ(S1) and E(T1) values, as well as the smallest ΔE(S1-T1) value could result in higher phosphorescent quantum efficiency for 1b than those of other complexes.

A DFT/time-dependent DFT (TD-DFT) investigation was conducted on a series of cationic iridium(III) complexes with 2-phenylpyridine (ppy n ) derivatives and a diphosphane (_ PP n ) ancillary ligand to shed light on the effects of stereoisomerism and ligand substituents on the photophysical properties. The geometries, electronic structures, lowest-lying singletsinglet absorptions, vertical singlet-triplet excitations, and triplet-singlet emissions of N,N-cis-[Ir(ppy 0 ) 2 (_ PP)] + (1), N,Ntrans-[Ir(ppy 0 ) 2 (_ PP)] + (2) and their derivatives were investigated with DFT-based approaches [ppy 0 = 2-phenylpyridine, _ PP = 1,2-bis(diphenylphosphanyl)ethene]. The complex N,Ntrans-[Ir(ppy 2 ) 2 (_ PP 2 )] + (3b) shows high quantum phosphorescence efficiency (Φ PL ) of 91 %, whereas an extremely low Φ PL (Ͻ1 %) was observed for N,N-trans-[Ir(ppy 4 ) 2 (_ PP 1 )] + (2d). To clarify this behavior, the S 1 -T n splitting energy (ΔE S 1 -T n ), the transition dipole moment (μ S 1 ) upon the S 0 ǞS 1 transition, and the energy gap between the triplet metal-to-ligand charge [a]

The ginkgo leaf-derived graphitic-N-doped porous carbon was fabricated by one-step carbonization in the presence of KOH agent. The morphology, surface functional groups, element state and porous structure of the obtained carbon were investigated systematically. Compared with the carbon samples by ginkgo-leaf carbonization and KOH post-activation (two-step), the one-step activated porous carbon exhibits high graphitic-N content and good electric conductivity. The conductive-agent-free carbon sheet was made successfully and the resultant carbon electrode possesses good conductivity and excellent electrochemical properties, with the specific capacitance of 176.1 F g −1 . When being applied for capacitive deionization, the desalination amount of the electrode arrived at 16.5 mg g −1 . Meanwhile, the salt adsorption rate is very rapid, with the average salt adsorption rate reaching 1.5 mg g −1 min −1 . This work provides an easy and environmentally benign route for the synthesis of the conductive carbon from natural raw materials for highly efficient capacitive deionization.