Anisotropic N-Graphene-diffused Co₃O₄ nanocrystals with dense upper-zone top-on-plane exposure facets as effective ORR electrocatalysts

We provide strong evidence of the effectiveness of homogenously self-propelled particle-in-particle diffusion, interaction and growth protocol. This technique was used for one-pot synthesis of novel nitrogen-graphene oxide (N-GO)/Co₃O₄ nanocrystals with cuboid rectangular prism-shaped nanorods (NRs) along {110}-plane and truncated polyhedrons with densely-exposed, multi-facet sites along {311} and {111} planes. These hierarchal nanocrystals create electrode catalyst patterns with vast-range accessibility to active Co²⁺ sites, a vascular system for the transport and retention of captured O₂ molecule interiorly, and low adsorption energy and dense electron configuration surfaces during the oxygen reduction reaction (ORR). The superior electrocatalytic ORR activity of the N-GO/Co₃O₄ polyhedron nanocrystals in terms of electrochemical selectivity, durability and stability compared with NRs or commercial Pt/C catalysts confirms the synergetic contribution of multi-functional, dense-exposed, and actively topographic facets of polyhedrons to significantly activate the catalytic nature of the catalyst. Our findings show real evidence, for the first time that not only the large number of catalytically active Co²⁺ cations at the top surface layer but also the dense location of active Co²⁺ sites on the upper-zone top-on-plane exposure, and the electron density configuration and distribution around the Co²⁺ sites were important for effective ORR.