The reactive and stable catalysts for the oxygen reduction reaction are highly desirable for low temperature fuel cells. The commercial oxygen reduction reaction electrocatalysts generally reply on noble metal based nanomaterials, which suffer from inherent cost and selectivity issues. At present, it still remains challenge for designing efficient non-noble metal-based oxygen reduction reaction electrocatalysts. Herein, we successfully synthesize Co nanoparticles supported on three-dimensionally N-doped holey graphene aerogels hybrids by the high-temperature calcination of the graphene aerogels-polyallylamine-Co II hybrids. The component optimized hybrids show the excellent electrocatalytic activity for oxygen reduction reaction in alkaline media, which is comparable to commercial Pt/C electrocatalyst. Meanwhile, the hybrids also show eminent tolerance for CO and methanol, attributing to their excellent oxygen reduction reaction selectivity. The three-dimensionally interconnected structure of graphene aerogels, N-doping, uniform dispersion and high crystallinity of Co nanoparticles, and holey structure of graphene contribute to the striking oxygen reduction reaction activity of hybrids.
Low temperature co-fired ceramics (LTCC) technology is extensively utilized to meet the requirements of device integration and miniaturization. Low-fired Li 3 Mg 2 NbO 6 ceramics doped with x wt% Li 2 O–MgO–B 2 O 3 –CaF 2 –SiO 2 glass (LMBCS, x = 0.5, 1.0, 1.5, 2.0) were prepared by the solid-state reaction method for applications in microwave communication materials. All samples exhibited a single-phase Li 3 Mg 2 NbO 6 structure. The addition of LMBCS glass effectively reduced the sintering temperature of Li 3 Mg 2 NbO 6 ceramics from 1250 °C to 875 °C. And adding LMBCS glass improved the Q × f value of Li 3 Mg 2 NbO 6 ceramics. The Li 3 Mg 2 NbO 6 -1.0wt% LMBCS ceramics exhibited outstanding microwave dielectric properties: ε r = 16.8, Q × f = 89,495 GHz, τ f = − 27.4 ppm/°C at 875 °C, which indicates that this ceramic is potential candidate materials for LTCC.
The adsorption-catalysis synergy for accelerated conversion of polysulfides is critical toward the electrochemical stability of lithium-sulfur battery (LSB). Herein, a non-metallic polymer network with anion receptor units, trifluoromethanesulfonyl (CF 3 SO 2 -) substituted aza-ether, was in-situ integrated on PE separator, working as an efficient host for anchoring lithium thiophosphates (LPS) as redox mediators and polysulfides through Lewis acid-base interaction. The anchored LPS on the modified PE separator displayed a robust chemical adsorption ability towards polysulfides through the formation of S S bond. Meanwhile, LPS decreased the energy barrier of Li 2 S nucleation and promoted redox reaction kinetics. The battery with LPS decorated separator revealed a long cycling lifespan with a per cycle decay of 0.056 % after 600 cycles, and a competitive initial capacity of 889.1 mAh/g when the of sulfur cathode increased to 3 mg cm −2 . This work developed a new design strategy to promote the utilization of lithium phosphorus sulfide compounds in LSB.
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