Coordination-Self-Assembly Approach Toward Transition Metal-Ordered Mesoporous Carbon Nanocomposites For Electrochemical Application

Multifunctional ordered mesoporous carbon materials that feature high surface area,uniform pores,good conductivity of carbon skeletons and specific host-gust interactions,which are of interest for a wide variety of applications,for instance catalysis,photonics,bioscience and energy storage.Here we establish a facile and generalizable “coordination-assisted self-assembly” for encapsulation of aggregationfree and highly dispersed metal nanoparticles inside the mesoporous carbon frameworks.The choice of pyrogallol as phenolic resin precursor is essential for the in situ encapsulation,because the strong coordination between the three hydroxide groups of pyrogallol and metal ions favors the immobilization of transition metal into the mesopores,and then suppress the sintering of metal nanoparticles at high carbonization temperatures.The metal supported mesoporous composites possess the very high loading content of 1.25%-7.27%,tiny particle sizes of 4.3-15.6 nm and high surface area of 475-589 m2 g-1.The unique structure in deed endows high sulfur loading content in the conductive mesoporous carbon channels,and meanwhile metal nanoparticles as catalyst effectively promotes the electrochemical conversion of polysulfides,resulting in a high reversible capacity,excellent rate capability and good cycling stability for Li-S batteries.The N-doped metal-OMC nanocomposites were synthesized through a simple ammonia-active step to dope nitrogen into the metal-OMC nanocomposites,which leads to higher electrochemical catalysis activities of the products.In consider of that the well-dispersed nanoparticles can be maintained under a high pyrolysis temperature,the calcining temperature was lift to 850 oC to get products with higher graphitization level which endows metal-OMC nanocomposites better electroconductivity.The Ndoped metal-OMC nanocomposites exhibit favorable performance for hydrogen evolution reaction(HER)in both acid and alkaline electrolyte.It delivered a current density of 10 m A cm-2 at the overpotential of 180 m V in 1 M KOH and 188 m V in 0.5 M H2SO4 electrolyte.The transition metal nanoparticles embedded in the mesoporous wall were protected from corrosion of electrolyte.Therefore,the nanocomposites exhibit excellent stability.The catalyst could sustain potentiostatic electrolysis for at least 20 hours at 10 m A cm-2 in both acidic and alkaline solutions.