Single Crystalline Co(3)O(4) Nanocrystals Exposed with Different Crystal Planes for Li-O(2) Batteries

Single crystalline Co(3)O(4) nanocrystals exposed with different crystal planes were synthesised, including cubic Co(3)O(4) nanocrystals enclosed by {100} crystal planes, pseudo octahedral Co(3)O(4) enclosed by {100} and {110} crystal planes, Co(3)O(4) nanosheets exposed by {110} crystal planes, hexagonal Co(3)O(4) nanoplatelets exposed with {111} crystal planes, and Co(3)O(4) nanolaminar exposed with {112} crystal planes. Well single crystalline features of these Co(3)O(4) nanocrystals were confirmed by FESEM and HRTEM analyses. The electrochemical performance for Li-O(2) batteries shows that Co(3)O(4) nanocrystals can significantly reduce the discharge-charge over-potential via the effect on the oxygen evolution reaction (OER). From the comparison on their catalytic performances, we found that the essential factor to promote the oxygen evolution reactions is the surface crystal planes of Co(3)O(4) nanocrystals, namely, crystal planes-dependent process. The correlation between different Co(3)O(4) crystal planes and their effect on reducing charge-discharge over-potential was established: {100} < {110} < {112} < {111}.