Well-defined carbon polyhedrons prepared from nano metal-organic frameworks for oxygen reduction

We report a nanostructured electrocatalyst engineered from molecular design and morphology evolution. Using a typical Co-based metal-organic framework, ZIF-67, nanocrystals were precisely synthesized with tunable size and morphology. Nitrogen-doped carbon nano polyhedrons decorated with cobalt nanoparticles were fabricated via pyrolysis of ZIF-67 and the carbonized products inherited the nanosize and shape of the MOF precursor. The intense effect of size on the electrocatalytic activity and transport properties was systematically investigated. The catalyst derived from the smallest MOF (300 nm), exhibited superior performance towards oxygen reduction with an onset potential of 0.86 V and a half-wave potential of 0.71 V in acidic solution, which are comparable to the best carbon-based oxygen reduction reaction (ORR) catalysts. This work will pave the way for the development of MOF-derived energy materials in various fields such as fuel cells and Li-air batteries, and opens new avenues for the design of MOFs in electrochemical applications.