A stability study of impregnated LSCF–GDC composite cathodes of solid oxide fuel cells

The performance degradation of composite cathodes of La0.6Sr0.4Co0.2Fe0.8O3−δ and Gd-doped ceria (LSCF–GDC), prepared by impregnating the porous GDC scaffold with a nitrate solution containing La, Sr, Co and Fe in desired composition, is investigated at 750 °C and open circuit in air for 500 h. The performance of the impregnated LSCF–GDC composite cathodes deteriorates after testing at 750 °C for 500 h; the electrode polarization resistance (Rp) increases from 0.38 to 0.83 Ω cm2, and the electrode ohmic resistance (Ro) increases from 1.79 to 2.14 Ω cm2. The grain growth and coarsening of impregnated LSCF nanoparticles are responsible for the performance degradation of the cathodes. XPS analysis shows the enrichment of cobalt on the surface of the infiltrated LSCF–GDC cathodes and such surface segregation could also contribute to the degradation of the electrocatalytic activity of the cathodes. Introducing MgO and LaNi0.6Fe0.4O3 phases can effectively suppress the coarsening of LSCF nanoparticles and enhance the stability of the cathodes. However, the enhancing effect is related to the conductivity and electrocatalytic activity of the introduced phases

Challenging National Narratives: On the Origins of Sweet Potato in China as Global Commodity During the Early Modern Period

The introduction of American cereal crops is probably one of the most important events in China¿s agricultural history, having a great effect on the agriculture production, national life, the transformation of consumer behaviour and, to some extent, the nationalization of consumption. The sweet potato (Ipomoea Batatas L.), in Chinese g¿nsh¿ ¿¿, is a staple food crop for ancient Chinese society. Today it still plays an important role in Chinese daily life, as well as guaranteeing national food security.GECEM Project, Global Encounters between China and Europe: Trade Networks, Consumption and Cultural Exchanges in Macau and Marseille (1680-1840), ERC (European Research Council)- Starting Grant, programa Horizon 2020, número de ref. 679371, www.gecem.eu.Versión del edito

Tailoring Excited-State Properties and Electroluminescence Performance of Donor–Acceptor Molecules through Tuning the Energy Level of the Charge-Transfer State

Three donor–acceptor (D–A) compounds (PTZ-10-AnP, PTZ-10P-AnP, and PTZ-3-AnP) were designed and synthesized through linking the same D and A units with different architectures. The structural change, mainly referring to the torsion angle and distance between D and A, gives rise to the significantly different CT level positions for these compounds. The CT state of PTZ-10-AnP locates at the lowest excited state, while that of PTZ-10P-AnP stays at the higher excited state. For PTZ-3-AnP, the CT energy is close to that of the locally π–π* excited state, and a hybridized local and charge-transfer (HLCT) state dominates the S₁ state. Photophysical experiment data of these compounds demonstrate that the energy level of the charge-transfer (CT) state plays a decisive role in the emissive state properties of donor–acceptor (D–A) compounds. In addition, the exciton utilization efficiency of the PTZ-3-AnP device exceeds the limit of the spin statistics, which enlightens the molecular design toward harvesting triplet excitons in fluorescent organic light-emitting diodes (OLEDs)