Current battery technology urgently requires improvement for higher energy density applications such as electric vehicles. Lithium-oxygen (Li-O2) battery is a promising alternative but still far from commercialization. It is highly expected that cathode kinetics be accelerated with the assistance of electrocatalysts. Tailoring the electrochemical interface is critical in improving the catalytic activity and controlling product selectivity for high-performance energy conversion and storage. Here we show the co-facially solvothermal docking of ultrathin (&lt;3 nm) cobalt-porphyrin-based 2D metal-organic framework (MOF) on few-layer nitrogen-doped graphene (NG). MOF@NG is behaved as the electrocatalytic cathode in the Li-O2 battery for the first time, demonstrating large discharge capacity of 3895 mAh g-1, an overpotential 60 mV, round-trip efficiency of 57.9% and stable cycling performance for almost 2 days. Well crystallized MOF structure offers enormous amounts of cavities for O2 adsorption. NG with higher conductivity greatly lowers the charge transfer resistance, enlarges the ECSA and accelerates the electron transfer from the electrocatalyst to O2. Most importantly, the cross-interfacial electronic interplay between MOF and NG around Co(II) site actives its performance and accelerates the oxygen reduction reaction in terms of positively shifted onset potential by 200 mV and increased mass activity by 4-fold compared to sole MOF. This work highlights the mechanism of tailoring 2D interfaces promotes the rate of oxygen reduction for Li-O2 battery.

Steering oxygen reduction pathways by docking cobalt-porphyrin nanogrids on graphene

256th National Meeting (2018)

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