Enhanced Li-O2 battery performance using NiS/MoS2 heterostructure by building internal electric field to promote the one-electron oxygen reduction/oxidation.

Electrocatalysts with appropriate electron coupling toward LiO2 intermediates can exhibit superior oxygen reduction/evolution reaction kinetics in Li-O2 batteries (LOBs). In this work, a charge redistribution strategy has been developed by constructing NiS/MoS2 heterostructure nanosheet self-assembled hollow microspheres with an internal electric field to regulate the interaction with LiO2 and then improve the electrochemical performance of LOBs. Density functional theory calculations and physicochemical characterizations reveal that the difference of work functions between NiS and MoS2 promotes the electron redistribution in heterointerface via built-in electrical field, leading to increased electron density of interfacial Ni atom, thereby enhancing its electron coupling toward LiO2 intermediates and promoting one-electron oxygen reduction/oxidation reaction kinetics. As a result, the NiS/MoS2-based LOBs exhibit evidently higher discharge capacity and much better cycling performance than the batteries using NiS and MoS2. This work provides a reliable charge redistribution strategy induced by build-in electric field to design efficient catalysts for LOBs.

Modulating Electronic Structure with Copper Doping to Promote the Electrocatalytic Performance of Cobalt Disulfide in Li-O2 Batteries.

Introducing heteroatom into catalyst lattice to modulate its intrinsic electronic structure is an efficient strategy to improve the electrocatalytic performance in Li-O2 batteries. Herein, Cu-doped CoS2 (Cu-CoS2 ) nanoparticles are fabricated by a solvothermal method and evaluated as promising cathode catalysts for Li-O2 batteries. Based on physicochemical analysis as well as density functional theory calculations, it is revealed that doping Cu heteroatom in CoS2 lattice can increase the covalency of the CoS bond with more electron transfer from Co 3d to S 3p orbitals, thereby resulting in less electron transfer from Co 3d to O 2p orbitals of Li-O species, which can weaken the adsorption strength toward Li-O intermediates, decrease the reaction barrier, and thus improve the catalytic performance in Li-O2 batteries. As a result, the battery using Cu-CoS2 nanoparticles in the cathode exhibits superior kinetics, reversibility, capacity, and cycling performance, as compared to the battery based on CoS2 catalyst. This work provides an atomic-level insight into the rational design of transition-metal dichalcogenide catalysts via regulating the electronic structure for high-performance Li-O2 batteries.

Multifunctional Catalyst CuS for Nonaqueous Rechargeable Lithium-Oxygen Batteries.

Copper sulfide with flower-like (f-CuS) and carambola-like (c-CuS) morphologies was successfully synthesized by a facile one-step solvothermal route with different surfactants. When employed as cathode catalysts for lithium-oxygen batteries (LOBs), f-CuS outperforms c-CuS in terms of oxygen electrochemistry, judging from the faster kinetics and the higher reversibility of oxygen reduction/oxidation reactions, as well as the better LOB performance. Moreover, an abnormal high-potential discharge plateau was observed in the discharge profile of the LOB. To understand the different performances of f-CuS and c-CuS and the abnormal high-potential plateau, theoretical calculations were conducted, based on which a mechanism was proposed and verified with experiments. On the whole, CuS can work as a multifunctional catalyst for promoting LOB performance, which means that the dissolved CuS in LiTFSI/TEGDME electrolyte can serve as a liquid catalyst by the redox couples of Cu(TFSI)2/Cu(TFSI)2-/Cu(TFSI)22-, in addition to the function as a traditional solid catalyst in the cathode.

Integrated miRNA-mRNA analysis provides potential biomarkers for selective breeding in bay scallop (Argopecten irradians).

Growth traits were compared between selected Argopecten irradians (BA) and non-selected A. irradians (NA; as a control). The results indicated that 1) the BA line exhibited greater average body weight and adductor muscle wet weight increase compared with the NA line at the same age of 10 months. 2) Comparative and integrated microRNA (miRNA) and mRNA transcriptome analyses identified 3373 differentially expressed genes (DEGs), 33 differentially expressed miRNAs (DEMs), and 39 "DEM-DEG" pairs in the BA line compared with the control. DEGs, DEMs, and "DEM-DEG" pairs involved in insulin signaling, immune related pathways, and actin cytoskeleton regulation were identified as candidates correlated with growth improvement in the BA line. A total of 259 positively selected genes were also identified. Collectively, our observations in this study will enrich the molecular information for A. irradians and provide potential biomarkers for future selective breeding and new seed creation in scallops.

Theoretical calculation assisted materials screening of BiOX (X = F, Cl, Br, I) for electrochemical absorption of cesium ions.

The electrochemical switching ion exchange (ESIX) technique has been widely used for the separation and recovery of radioactive cesium ions (Cs+) from wastewater. In this study, a series of BiOX (X = F, Cl, Br, I) materials were first evaluated for their absorption properties to Cs+ through density functional theory (DFT) calculations. The calculations predict that BiOBr has the best absorption performance among the four materials, BiOF, BiOCl, BiOBr, and BiOI, due to its high absorption energy and low ion migration energy barrier to Cs+. Simultaneously, the selectivity calculations revealed that BiOBr also showed the best selectivity for Cs+ compared with Li+ and Na+. Subsequently, four materials were prepared using the hydrothermal synthesis method and their electrochemical absorption performance was tested. The results showed that BiOBr has the highest electroactivity, and its absorption capacity was up to 16 mg Cs+/g BiOBr in a solution mixture of 50 ppm Li+, Na+, and Cs+. Based on our theoretical calculations and experiments, our findings provide prospective insights for predicting the electrochemical absorption performance of materials using first-principles calculations.

Theoretical and experimental investigations of BiOCl for electrochemical adsorption of cesium ions.

BiOCl was found to have excellent electrochemical adsorption properties for cesium ions (Cs+) in electrochemically switched ion exchange (ESIX). In this work, BiOCl nanosheets were synthesized by a hydrothermal method and used for electrochemical adsorption of Cs+. The experimental results showed that BiOCl exhibited higher electrochemical adsorption selectivity for Cs+ than Li+ and Na+. Quantum chemical calculations based on density functional theory (DFT) were first performed to compare the adsorption and migration mechanisms of three ions Li+, Na+, and Cs+ in BiOCl crystals. The calculation results revealed that the excellent electrochemical adsorption performance of BiOCl for Cs+ is due to the interaction of embedded Cs with Cl and Bi in BiOCl crystals. This makes it have a higher adsorption energy and a lower ion migration energy barrier due to the balance of interaction forces. In this work experimental and theoretical calculations were used to systematically analyze the adsorption and migration of three ions in BiOCl, which has important guiding significance for the design of highly-efficient electroactive materials for electrochemical adsorption of Cs+.

DFT calculations of the synergistic effect of λ-MnO2/graphene composites for electrochemical adsorption of lithium ions.

Recently, the composite of spinel-type manganese oxide (λ-MnO2)/graphene has drawn wide attention because of its good electrochemical adsorption selectivity for low concentrations of Li+ ions from lake brine or seawater to cope with the fast-rising demand of lithium resources. In this composite, the synergistic effect between the good selectivity of λ-MnO2 for Li+ ions and the excellent conductivity of graphene play an important role for the electrochemical adsorption of Li+ ions. In order to reveal the synergistic mechanism in the electronic conductivity, the ionic conductivity and the ion selectivity of the λ-MnO2/graphene composite, density functional theory (DFT) calculations combined with electrochemical adsorption experiments were carried out. The calculation results show that the enhanced electronic conductivity of the composite is due to the decrease of the band gap (Eg) in the λ-MnO2/graphene composite compared with pure λ-MnO2. Meanwhile, the graphene composited with λ-MnO2 decreased the diffusion energy barrier of Li+ ions in λ-MnO2. In addition, the competitive adsorption of Li+, Na+ and Mg2+ ions were investigated by the nudged elastic band (NEB) method and charge distribution analysis. The results show that Li+ ions in λ-MnO2 exist in their pure ion state and have the lowest diffusion energy barrier compared with Na+ and Mg2+. The results of the DFT calculations were validated by cyclic voltammetry, electrochemical impedance spectroscopy and electrochemical adsorption experiments.

Theoretical and experimental investigations of the electronic/ionic conductivity and deprotonation of Ni3-xCoxAl-LDHs in an electrochemical energy storage system.

The remarkable effect of divalent transition metal ions on the electrochemical performance of transition metal-based layered double hydroxides (LDHs) was systematically investigated via computational and experimental approaches. Ni3-xCoxAl-LDHs (x = 0, 1, 2, and 3) were synthesized on carbon paper by a unipolar pulse electrodeposition (UPED) method and used as electrodes in energy storage systems. The structures were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Their electrochemical performance was evaluated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The mechanism of different electrochemical performances with various divalent transition metal ions was investigated by the density functional theory (DFT) plus U method and molecular dynamics (MD) simulations. The computational and experimental data demonstrated that the electronic and ionic conductivity and deprotonation of NiAl-LDHs were improved by doping Co species, and the incorporation of Co and Ni cations enabled LDHs to exhibit a larger interlayer spacing which can facilitate the diffusion of OH- ions, indicating that NiCo2Al-LDHs had the highest specific capacitance.

Potential-induced reversible uptake/release of perchlorate from wastewater by polypyrrole@CoNi-layered double hydroxide modified electrode with proton-ligand effect.

In this study, CoNi-layered double hydroxide (CoNi-LDH) nanosheets coated conducting polypyrrole (PPy) nanowire was controllably fabricated on Pt plate or carbon cloth by using unipolar pulse electrodeposition (UPED) method and served as a novel electrochemically switched ion exchange (ESIX) hybrid film with proton-ligand effect for the removal of perchlorate anions (ClO4-). It is expected that the space among CoNi-LDH nanosheets of the shell could act as the reservoir for the anions while the PPy core serve as the potential-induced element for proton-ligand. The effects of pulse potential during film deposition and initial pH of the wastewater on the ClO4- removal performance of this core-shell hybrid film were investigated. It is found that ClO4- adsorption onto PPy@CoNi-LDH followed pseudo-second-order model, and the film fabricated with -1.5 V pulse potential showed an excellent performance for the rapid removal of ClO4- with a high selectivity, and the ClO4- adsorption quantity reached as high as 302 mg g-1. In a wide pH range (3-10), the hybrid film removed ClO4- efficiently. The proton-ligand effect in PPy@CoNi-LDH was proved by using XPS analysis and density functional theory. Such a PPy@CoNi-LDH hybrid core-shell film should be a potential electroactive material for the separation of ClO4- and other anions from wastewater.