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.

Pd@Pt Core-Shell Concave Decahedra: A Class of Catalysts for the Oxygen Reduction Reaction with Enhanced Activity and Durability.

Abstract: We report a facile synthesis of multiply twinned Pd@Pt core-shell concave decahedra by controlling the deposition of Pt on preformed Pd decahedral seeds. The Pt atoms are initially deposited on the vertices of a decahedral seed, followed by surface diffusion to other regions along the edges/ridges and then across the faces. Different from the coating of a Pd icosahedral seed, the Pt atoms prefer to stay at the vertices and edges/ridges of a decahedral seed even when the deposition is conducted at 200 °C, naturally generating a core-shell structure covered by concave facets. The nonuniformity in the Pt coating can be attributed to the presence of twin boundaries at the vertices, as well as the {100} facets and twin defects along the edges/ridges of a decahedron, effectively trapping the Pt adatoms at these high-energy sites. As compared to a commercial Pt/C catalyst, the Pd@Pt concave decahedra show substantial enhancement in both catalytic activity and durability toward the oxygen reduction reaction (ORR). For the concave decahedra with 29.6% Pt by weight, their specific (1.66 mA/cm(2)Pt) and mass (1.60 A/mgPt) ORR activities are enhanced by 4.4 and 6.6 times relative to those of the Pt/C catalyst (0.36 mA/cm(2)Pt and 0.32 A/mgPt, respectively). After 10,000 cycles of accelerated durability test, the concave decahedra still exhibit a mass activity of 0.69 A/mgPt, more than twice that of the pristine Pt/C catalyst.

Conversion of biomass to γ-valerolactone by catalytic transfer hydrogenation of ethyl levulinate over metal hydroxides

Abstract: National Basic Research Program of China [2010CB732201]; National Natural Science Foundation of China [21106121]; Provincial RD Fundamental Research Funds for the Central Universities [2010121077]; Key Programs for Cooperation Between Universities and Enterprises in Fujian Province [2013N5011]

Pyrolyzed Fe–N–C Composite as an Efficient Non-precious Metal Catalyst for Oxygen Reduction Reaction in Acidic Medium

Abstract: Aimed at developing a highly active and stable non-precious metal catalyst (NPMC) for oxygen reduction reaction (ORR) in acidic proton-exchange membrane fuel cells (PEMFCs), a novel NPMC was prepared by pyrolyzing a composite of carbon-supported Fe-doped graphitic carbon nitride (Fe–g-C3N4@C) above 700 °C. In this paper, the influence of the pyrolysis temperature and Fe content on ORR performance was investigated. Rotating disk electrode (RDE) and rotating ring-disk electrode (RRDE) studies reveal that, with a half-wave potential of 0.75 V [versus reversible hydrogen electrode (RHE)] and a H2O2 yield of 2.6% at 0.4 V, the as-synthesized catalyst heat-treated at 750 °C with a Fe salt/dicyandiamide (DCD) mass ratio of 10% displays the optimal ORR activity and selectivity. Furthermore, the pyrolyzed Fe–N–C composite exhibits superior durability in comparison to that of commercial 20 wt % Pt/C in acidic medium, making it a good candidate for an ORR electrocatalyst in PEMFCs.

High Voltage Operation of Ni-Rich NMC Cathodes Enabled by Stable Electrode/Electrolyte Interphases

Abstract: DOI: 10.1002/aenm.201800297 high theoretical specific capacity (3860 mA h g−1), and the lowest negative electrochemical potential (−3.040 V vs the standard hydrogen electrode).[1] Rechargeable Li metal batteries (LMBs), regarded as one of the most promising candidates for next-generation high-energy-density energy storage systems, have been widely investigated since the 1970s.[2] In fact, the Li metal anode (LMA) is indispensable in the research and development of Li–sulfur, Li–air, and solid-state Li batteries.[1,3] Recently, significant progress has been made on high efficiency operation of LMAs, including the modification of electrolyte chemistry,[4,5] use of concentrated electrolytes or additives,[6] selective Li deposition,[2c] application of polymer or solid-state electrolytes,[7] and novel configurations of LMA protection.[2c,8] Recently, a high concentration electrolyte [4 m lithium bis(fluorosulfonyl)imide (LiFSI) in 1,2-dimethoxyethane (DME)] has been reported to enable high rate cycling of Li||Cu cell with a high Coulombic efficiency (CE) of up to 99.1% without dendrite growth.[6b] This was attributed to the preferential decomposition of LiFSI salt that forms a LiF-rich solid electrolyte interphase (SEI) layer, which is beneficial to stabilize the Li metal anode/electrolyte interface, uniform growth of Li films, and suppress the further corrosion of Li metal. In contrast, DME solvent will be decomposed first in a low concentration LiFSI/DME electrolyte and forms a less stable SEI layer dominated by polymeric components. However, ether-based electrolytes are less suitable with the high voltage (>4 V) cathode required for high-energy-density batteries due to their low oxidation potentials. In this regard, carbonate-based electrolytes are a better choice for high-voltage, high-energy-density LMBs. Our recent work on carbonated-based electrolytes revealed that a dual-salt electrolyte of lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) and lithium bis(oxalato)borate (LiBOB) in a carbonate solvent mixture with 0.05 m LiPF6 additive can greatly improve the stability of Li metal and suppress Li dendrite formation even at high current densities.[9] However, the energy density of this LMB system is still relatively low owing to the use of LiNi0.4Mn0.4Co0.2O2 (NMC442), which exhibits a limited discharge capacity of ≈160 mA h g−1 at C/10 when charged to 4.3 V, corresponding to a limited energy density of ≈610 W h kg−1. In order to achieve a higher energy density in LMBs, the most effective strategy is to develop cathode The lithium (Li) metal battery (LMB) is one of the most promising candidates for next-generation energy storage systems. However, it is still a significant challenge to operate LMBs with high voltage cathodes under high rate conditions. In this work, an LMB using a nickel-rich layered cathode of LiNi0.76Mn0.14Co0.10O2 (NMC76) and an optimized electrolyte [0.6 m lithium bis(trifluoromethanesulfonyl)imide + 0.4 m lithium bis(oxalato)borate + 0.05 m LiPF6 dissolved in ethylene carbonate and ethyl methyl carbonate (4:6 by weight)] demonstrates excellent stability at a high charge cutoff voltage of 4.5 V. Remarkably, these Li||NMC76 cells can deliver a high discharge capacity of >220 mA h g−1 (846 W h kg−1) and retain more than 80% capacity after 1000 cycles at high charge/discharge current rates of 2C/2C (1C = 200 mA g−1). This excellent electrochemical performance can be attributed to the greatly enhanced structural/interfacial stability of both the Ni-rich NMC76 cathode material and the Li metal anode using the optimized electrolyte.