Nankai University

About: Nankai University is a education organization based out in Tianjin, China. It is known for research contribution in the topics: Catalysis & Adsorption. The organization has 42964 authors who have published 51866 publications receiving 1127896 citations. The organization is also known as: Nánkāi Dàxué.

Single Nickel Atoms on Nitrogen-Doped Graphene Enabling Enhanced Kinetics of Lithium-Sulfur Batteries.

Abstract: Lithium-sulfur (Li-S) batteries have arousing interest because of their high theoretical energy density. However, they often suffer from sluggish conversion of lithium polysulfides (LiPS) during the charge/discharge process. Single nickel (Ni) atoms on nitrogen-doped graphene (Ni@NG) with Ni-N4 structure are prepared and introduced to modify the separators of Li-S batteries. The oxidized Ni sites of the Ni-N4 structure act as polysulfide traps, efficiently accommodating polysulfide ion electrons by forming strong Sx 2- ⋅⋅⋅NiN bonding. Additionally, charge transfer between the LiPS and oxidized Ni sites endows the LiPS on Ni@NG with low free energy and decomposition energy barrier in an electrochemical process, accelerating the kinetic conversion of LiPS during the charge/discharge process. Furthermore, the large binding energy of LiPS on Ni@NG also shows its ability to immobilize the LiPS and further suppresses the undesirable shuttle effect. Therefore, a Li-S battery based on a Ni@NG modified separator exhibits excellent rate performance and stable cycling life with only 0.06% capacity decay per cycle. It affords fresh insights for developing single-atom catalysts to accelerate the kinetic conversion of LiPS for highly stable Li-S batteries.

Fluorescent Metal–Organic Framework MIL-53(Al) for Highly Selective and Sensitive Detection of Fe3+ in Aqueous Solution

Abstract: Fluorescent metal–organic frameworks (MOFs) have received great attention in sensing application. Here, we report the exploration of fluorescent MIL-53(Al) for highly selective and sensitive detection of Fe3+ in aqueous solution. The cation exchange between Fe3+ and the framework metal ion Al3+ in MIL-53(Al) led to the quenching of the fluorescence of MIL-53(Al) due to the transformation of strong-fluorescent MIL-53(Al) to weak-fluorescent MIL-53(Fe), allowing highly selective and sensitive detection of Fe3+ in aqueous solution with a linear range of 3–200 μM and a detection limit of 0.9 μM. No interferences from 0.8 M Na+; 0.35 M K+; 11 mM Cu2+; 10 mM Ni2+; 6 mM Ca2+, Pb2+, and Al3+; 5.5 mM Mn2+; 5 mM Co2+ and Cr3+; 4 mM Hg2+, Cd2+, Zn2+, and Mg2+; 3 mM Fe2+; 0.8 M Cl–; 60 mM NO2– and NO3–; 10 mM HPO42–, H2PO4–, SO32–, SO42–, and HCOO–; 8 mM CO32–, HCO3–, and C2O42–; and 5 mM CH3COO– were found for the detection of 150 μM Fe3+. The possible mechanism for the quenching effect of Fe3+ on the fluorescence o...

Dark energy: Vacuum fluctuations, the effective phantom phase, and holography

Abstract: We aim at the construction of dark energy models without exotic matter but with a phantomlike equation of state (an effective phantom phase) The first model we consider is decaying vacuum cosmology where the fluctuations of the vacuum are taken into account In this case, the phantom cosmology (with an effective, observational $\ensuremath{\omega}$ being less than $\ensuremath{-}1$ ) emerges even for the case of a real dark energy with a physical equation of state parameter $\ensuremath{\omega}$ larger than $\ensuremath{-}1$ The second proposal is a generalized holographic model, which is produced by the presence of an infrared cutoff It also leads to an effective phantom phase, which is not a transient one as in the first model However, we show that quantum effects are able to prevent its evolution towards a big rip singularity

Identifying the Key Role of Pyridinic-N-Co Bonding in Synergistic Electrocatalysis for Reversible ORR/OER.

Abstract: For many regenerative electrochemical energy-conversion systems, hybrid electrocatalysts comprising transition metal (TM) oxides and heteroatom-doped (e.g., nitrogen-doped) carbonaceous materials are promising bifunctional oxygen reduction reaction/oxygen evolution reaction electrocatalysts, whose enhanced electrocatalytic activities are attributed to the synergistic effect originated from the TM-N-C active sites. However, it is still ambiguous which configuration of nitrogen dopants, either pyridinic or pyrrolic N, when bonded to the TM in oxides, predominately contributes to the synergistic effect. Herein, an innovative strategy based on laser irradiation is described to controllably tune the relative concentrations of pyridinic and pyrrolic nitrogen dopants in the hybrid catalyst, i.e., NiCo2 O4 NPs/N-doped mesoporous graphene. Comparative studies reveal the dominant role of pyridinic-NCo bonding, instead of pyrrolic-N bonding, in synergistically promoting reversible oxygen electrocatalysis. Moreover, density functional theory calculations provide deep insights into the corresponding synergistic mechanism. The optimized hybrid, NiCo/NLG-270, manifests outstanding reversible oxygen electrocatalytic activities, leading to an overpotential different ΔE among the lowest value for highly efficient bifunctional catalysts. In a practical reversible Zn-air battery, NiCo/NLG-270 exhibits superior charge/discharge performance and long-term durability compared to the noble metal electrocatalysts.

Graphene-based conducting inks for direct inkjet printing of flexible conductive patterns and their applications in electric circuits and chemical sensors

Abstract: A series of inkjet printing processes have been studied using graphene-based inks. Under optimized conditions, using water-soluble single-layered graphene oxide (GO) and few-layered graphene oxide (FGO), various high image quality patterns could be printed on diverse flexible substrates, including paper, poly(ethylene terephthalate) (PET) and polyimide (PI), with a simple and low-cost inkjet printing technique. The graphene-based patterns printed on plastic substrates demonstrated a high electrical conductivity after thermal reduction, and more importantly, they retained the same conductivity over severe bending cycles. Accordingly, flexible electric circuits and a hydrogen peroxide chemical sensor were fabricated and showed excellent performances, demonstrating the applications of this simple and practical inkjet printing technique using graphene inks. The results show that graphene materials-which can be easily produced on a large scale and possess outstanding electronic properties-have great potential for the convenient fabrication of flexible and low-cost graphene-based electronic devices, by using a simple inkjet printing technique.