Xiamen University

About: Xiamen University is a education organization based out in Amoy, Fujian, China. It is known for research contribution in the topics: Catalysis & Population. The organization has 50472 authors who have published 54480 publications receiving 1058239 citations. The organization is also known as: Amoy University & Xiàmén Dàxué.

Reversible multi-electron redox chemistry of π-conjugated N-containing heteroaromatic molecule-based organic cathodes

Abstract: Even though organic molecules with well-designed functional groups can be programmed to have high electron density per unit mass, their poor electrical conductivity and low cycle stability limit their applications in batteries. Here we report a facile synthesis of π-conjugated quinoxaline-based heteroaromatic molecules (3Q) by condensation of cyclic carbonyl molecules with o-phenylenediamine. 3Q features a number of electron-deficient pyrazine sites, where multiple redox reactions take place. When hybridized with graphene and coupled with an ether-based electrolyte, an organic cathode based on 3Q molecules displays a discharge capacity of 395 mAh g−1 at 400 mA g−1 (1C) in the voltage range of 1.2–3.9 V and a nearly 70% capacity retention after 10,000 cycles at 8 A g−1. It also exhibits a capacity of 222 mAh g−1 at 20C, which corresponds to 60% of the initial specific capacity. Our results offer evidence that heteroaromatic molecules with multiple redox sites are promising in developing high-energy-density, long-cycle-life organic rechargeable batteries. Organic compounds can be used as electrode materials for Li-ion batteries, but problems such as facile dissolution and low electrical conductivity hinder their application. Here the authors report π-conjugated quinoxaline-based heteroaromatic molecules with multiple redox sites to tackle the problems.

Strain engineering of thermal conductivity in graphene sheets and nanoribbons: a demonstration of magic flexibility

Abstract: Graphene is an outstanding material with ultrahigh thermal conductivity. Its thermal transfer properties under various strains are studied by reverse nonequilibrium molecular dynamics. Based on the unique two-dimensional structure of graphene, the distinctive geometries of graphene sheets and graphene nanoribbons with large flexibility and their intriguing thermal properties are demonstrated under strains. For example, the corrugation under uniaxial compression and helical structure under light torsion, as well as tube-like structure under strong torsion, exhibit enormously different thermal conductivity. The important robustness of thermal conductivity is found in the corrugated and helical configurations of graphene nanoribbons. Nevertheless, thermal conductivity of graphene is very sensitive to tensile strain. The relationship among phonon frequency, strain and thermal conductivity are analyzed. A similar trend line of phonon frequency dependence of thermal conductivity is observed for armchair graphene nanoribbons and zigzag graphene nanoribbons. The unique thermal properties of graphene nanoribbons under strains suggest their great potentials for nanoscale thermal managements and thermoelectric applications.

Z-Scheme Photocatalytic Systems for Carbon Dioxide Reduction: Where Are We Now?

Abstract: Transforming CO2 into fuels by utilizing sunlight is promising to synchronously overcome global warming and energy-supply issues. It is crucial to design efficient photocatalysts with intriguing features such as robust light-harvesting ability, strong redox potential, high charge-separation, and excellent durability. Hitherto, a single-component photocatalyst is incapable to simultaneously meet all these criteria. Inspired by natural photosynthesis, constructing artificial Z-scheme photocatalysts provides a facile way to conquer these bottlenecks. In this review, we firstly introduce the fundamentals of photocatalytic CO2 reduction and Z-scheme systems. Thereafter we discuss state-of-the-art Z-scheme photocatalytic CO2 reduction, whereby special attention is placed on the predominant factors that affect photoactivity. Additionally, further modifications that are important for efficient photocatalysis are reviewed.

NiCo Alloy Nanoparticles Decorated on N-Doped Carbon Nanofibers as Highly Active and Durable Oxygen Electrocatalyst

Abstract: The exploring of catalysts with high-efficiency and low-cost for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is one of the key issues for many renewable energy systems including fuel cells, metal–air batteries, and water splitting. Despite several decades pursuing, bifunctional oxygen catalysts with high catalytic performance at low-cost, especially the one that could be easily scaled up for mass production are still missing and highly desired. Herein, a hybrid catalyst with NiCo alloy nanoparticles decorated on N-doped carbon nanofibers is synthesized by a facile electrospinning method and postcalcination treatment. The hybrid catalyst NiCo@N-C 2 exhibits outstanding ORR and OER catalytic performances, which is even surprisingly superior to the commercial Pt/C and RuO2 catalysts, respectively. The synergetic effects between alloy nanoparticles and the N-doped carbon fiber are considered as the main contributions for the excellent catalytic activities, which include decreasing the intrinsic and charge transfer resistances, increasing CC, graphitic-N/pyridinic-N contents in the hybrid catalyst. This work opens up a new way to fabricate high-efficient, low-cost oxygen catalysts with high production.